Joint Education Initiative/Joint Education Initiative.iso/programs/dos/gna/gna.doc

Text File | 1990-06-25 | 172KB | 4,190 lines

                                                            Trademark
       Acknowledgements


       In  this documentation for the Geophysics of North America CD-ROM
       application,  trademarked  commercial products and companies  are
       named.  Mention of a commercial company or product does not imply
       endorsement  by  the  National Geophysical  Data  Center  or  the
       Department  of  Commerce.    Use  for  publicity  or  advertising
       purposes   of   information  from  this  publication   concerning
       proprietary  products  or  the  tests of  such  products  is  not
       authorized.

       Throughout the publication, rather than put a trademark symbol in
       every  occurrence  of a trademarked name,  we state that  we  are
       using the names only in an editorial fashion with no intention of
       infringement of the trademark.

       Trademarks  indicated  below were derived from  various  sources.
       The  National  Geophysical  Data  Center  cannot  attest  to  the
       accuracy nor completeness of this information.

       IBM  is  a  registered  trademark  and  PS/2,  VGA,  and  AT  are
       trademarks of International Business Machines Corporation.

       Macintosh is a trademark of Apple Computer, Inc.

       MS-DOS  and  Microsoft Extensions are  registered  trademarks  of
       Microsoft Corporation.

       WindowDOS is a registered trademark of WindowDOS Associates.

       Lotus is a registered trademark of Lotus Development Corporation.



       Disclaimer

       While  every  effort has been made to ensure that these data  are
       accurate  and reliable within the limits of the current state  of
       the art,  NOAA cannot assume liability for any damages caused  by
       any inaccuracies in the data or as a result of the failure of the
       data to function on a particular system.  NOAA makes no warranty,
       expressed   or  implied,   nor  does  the  fact  of  distribution
       constitute such a warranty.

       The  user  must be cautious when using these  data  and  computer
       programs.   None of the data represented here are perfect.  As in
       many complex scientific endeavors, errors can be expected.





                                       1


                                        Contents

       Prefacei

       Introductioniii
       Purpose of this Compilationiii
       Contacts for Suggestionsiii

       Chapter 1:  Getting Started1
       Setting Up Your Computer1
       Using the Compact Disc2
       Loading Access Software3
       Running the Tutorial5
       For Additional Help5

       Chapter 2:  User Instructions7
       Introduction7
       Learning the Menu Structure8
       Menu Structure Overview9
       The Main Menu9
       Data Display11
       Default Color Palettes12
       Changing the Palette13
       Changing the Area15
       Displaying the Image17
       Point Data17
       Contours20
       Boundaries21
       Saving and Restoring an Image22
       Special Features23
       Data Utilities26

       Chapter 3:  Technical Specifications27
       Data Formats on the Compact Disc27
       Directory Structure of the Compact Disc27

       Chapter 4:  Data Preparation Techniques33
       Philosophy of Data Preparation33
       Gridded Data33
       Topographic 30-Second Grid Data33
             Regridding Arrays34
       DNAG Magnetics Data for North America35
       Point Data35
       DNAG Seismicity Data35
       Crustal Stress Data37
       DNAG Thermal Aspects Data37
       Contour Data38
       Geographic Binning39
       Binning Point Data40
       Binning Geopolitical Boundary Data40
       Binning Contour Data41





                                       2


       Chapter 5:  History of Data Compilation43
       Decade of North American Geology Overview43
       Data Compilation Efforts45
       Potential Fields Data45
       SEG Gravity Data for the United States45
       Isostatic Gravity Data for the United States47
       DNAG Gravity Data for North America49
       DNAG Magnetics Data for North America49
       MAGSAT Data for North America55
       Topographic Data60
       Average Elevations and Bathymetry60
        Topography Data for the United States60
       Lithospheric Data62
       DNAG Seismicity Data62
       Crustal Stress Data for North America65
       DNAG Thermal Aspects Data66
       NOAA AVHRR Data67
       Satellite Radiometric Data67
       Normalized Vegetation Index (NVI) Data68

       Chapter 6:  Your Data Center for Solid Earth Geophysics69
       Program Overview69
       World Data Center A70
       Visiting Scientists Program70
       Cooperative Institutes70
       Staff Credits72

       Appendix A:  Directory Tree73

       Appendix B:  Running Utilities81

       Release 1.1 Preface

       In  September 1989,  the original Geophysics of North America CD-
       ROM  was  published  by  the  National  Oceanic  and  Atmospheric
       Administration (NOAA).   This quickly became a popular product in
       the  academic community because it provided  an  intuitive,  user
       interface to vast amounts of Earth science data.

       Portions  of this data compilation have been selected for use  in
       the JEDI (Joint Educational Initiative) Project.   These features
       include  all  of the display data (42% of the original data)  and
       associated access software.

       Please note that archival data have been eliminated from the JEDI
       Project  compilation.    The  archival  data  formats  frequently
       contained  higher resolutions (than those presented  for  graphic
       viewing)  and  more  informational  content.    The  data  output
       software has also been excluded.   This software allowed for data
       retrieval  and  output from the CD-ROM to  hard  disk.   Finally,
       geographically  partitioned  files have been omitted  (for  space
       considerations).   Because  of  this,  you  may  experience  some
       slowing  in  data  display features associated with  gravity  and
       magnetics images.


                                       3


       Release 1.1Introduction

       Introduction

       PURPOSE OF THIS COMPILATION

       The original Geophysics of North America compact disc project was
       an  outgrowth  of  numerous research efforts.   For more  than  a
       decade,  scientists,  their  professional  societies  (e.g.,  the
       Society  of Exploration Geophysicists and the Geological  Society
       of America),  and their governments (e.g., United States, Canada,
       and Mexico) have been working toward a consolidated collection of
       land and marine geophysical data for North America.  Much of this
       important work is represented in this data base.

       The National Geophysical Data Center (NGDC) appreciates the value
       of  integrated  data  management,  and assembled  data  for  this
       compact  disc  in  order  to  simplify  the  work  of  scientists
       performing regional geophysical studies.  The compact disc format
       was selected because it is capable of storing large quantities of
       data,  while  providing  easy and cost-effective retrieval  in  a
       workstation environment.

       Applications  for  the disc could include  analysis  of  regional
       trends,  or  analysis  of interrelationships between gravity  and
       magnetics in comparison with topography or earthquake seismicity.

       To encourage innovative use of the data,  we have included access
       software  that  simplifies data  selection.   The  software  also
       allows  the  user to obtain "quick-look" retrievals of the  data,
       complete with geographical references and data contour  overlays.

       This  publication  describes  the data contained on  the  compact
       disc, data sources and contributors, and access software provided
       on the accompanying diskettes.   Discussions of the hardware  and
       software environment are also presented.

       CONTACTS FOR SUGGESTIONS

       The  developers of this data compilation invite user comments  on
       all  aspects  of this product  -- format,  access  software,  and
       documentation.   Future projects of this kind are anticipated and
       we are eager to improve our services.

       Please forward general comments to:  Herbert Meyers, Chief, Solid
       Earth  Geophysics  Division,  National Geophysical  Data  Center,
       NOAA,  Code E/GC1,  325 Broadway,  Boulder,  Colorado 80303, USA.
       Telephone: [phone]; Fax: [phone].

       If  you have questions about the Geophysics of North America data
       base, please contact the following specialists at (303) 497-xxxx:

       End-user support6591Allen Hittelman
       System support6404John Kinsfather
       CD-ROM technology6276Carl Abston

                                       4


       Release 1.1Getting Started


       Getting Started


       SETTING UP YOUR COMPUTER

       The  access  software provided with this package will operate  on
       any  IBM PC/AT (286 or 386) or compatible personal computer  with
       an  Enchanced Graphics Adaptor (EGA) graphics board and a  CD-ROM
       reader.   The software is not designed to operate on other  types
       of computers (e.g.,  Macintosh).   However, the data files on the
       CD-ROM can be read on a Macintosh.

       NGDC uses CD-ROM drives made by Hitachi and SONY, with controller
       board,  connecting cable,  and applications software by Reference
       Technology.   This  applications  software  is  a  standard  file
       manager (STDFMAN, release 2.01 or higher) that interacts with the
       resident  PC Disk Operating System (DOS) to make the CD-ROM drive
       appear to be as a read-only disk drive.   Microsoft Extensions to
       DOS (release 2.0 or higher) are also used on some  systems.   The
       CD-ROM  readers  are  used  with a variety  of  PC/AT  compatible
       systems running at various speeds up to 25 MHz.   Various EGA/VGA
       graphics  boards  are used at NGDC,  although any  board  with  a
       standard EGA mode is adequate.

       A  single,  high-density  diskette drive and 3 megabytes of  hard
       disk  space  are required to load and execute  the  software.   A
       large-capacity  hard  disk  is needed if large files  are  to  be
       copied from the CD, or if many screen images are to be saved.  We
       recommend using a computer with at least 640 kilobytes of RAM and
       2  megabytes  of available hard disk.   The Geophysics  of  North
       America access software requires 450 kilobytes of free RAM.  This
       is  in addition to the CD-ROM reader application software  (e.g.,
       Reference   Technology's  Standard  File  Manager  (STDFMAN)   or
       Microsoft   Extensions  to  DOS).    A  math  co-processor   will
       significantly speed up the application.

       The  amount  of available RAM can be checked by issuing  the  DOS
       command  CHKDSK.   Depending on the software  configurations  for
       your  PC,  you  may not have 450 kilobytes available even  though
       there  are  640 kilobytes of installed RAM.   This can  often  be
       corrected  by  altering  parameters  in  your  CONFIG.SYS   file,
       AUTOEXEC.BAT  file,  or in STDFMAN.EXE.   Reducing the number  of
       assigned  buffers  and files in CONFIG.SYS will free up some  RAM
       but  a minimum of 10 files and 10 buffers are  recommended.   The
       access software will not run or the run will lock-up with too low
       a DOS file number.   Also, the I/O will be very slow with too few
       buffers.   STDFMAN.EXE  uses a default of four buffers  of  5,000
       bytes  each.   The recommended values for use with the Geophysics
       of  North  America software are one buffer (NDBUF=1)  and  buffer
       size 16,000 (DBSIZ=16000).



                                       5


       In  order  to  free up RAM,  you may need to  remove  any  device
       drivers  from  CONFIG.SYS not needed while running the  software.
       You  may  also  need to remove any resident  software  that  gets
       loaded automatically at boot time from AUTOEXEC.BAT.   Be sure to
       reboot  your PC after making any of the above changes and  before
       running the Geophysics of North America software.

       There are many possible computer,  EGA graphics board, and CD-ROM
       reader configurations;  some trial and error may be necessary  to
       get a compatible configuration.  This may require restrapping the
       CD-ROM   interface  board  to  change  the  I/O  address   and/or
       interrupt.   The driver software will then have to be modified to
       match the hardware configuration.   A special AUTOEXEC.BAT and/or
       CONFIG.SYS file may be needed on some PCs.

       Anyone  who  purchases a personal computer,  CD-ROM  reader,  and
       supporting  hardware and software is advised to check  how  these
       will  work  together as a system.   Each computer may  present  a
       slightly  different  problem  which  must be  solved  before  the
       complete system works successfully.   We have no experience  with
       using these devices with any PCs other than IBM PC/AT-compatibles
       that operate under DOS version 3.0 through 4.01.


       USING THE COMPACT DISC

       The Geophysics of North America files contain about 249 megabytes
       (249  million  characters) of data and information compiled  from
       many different source tapes available at NGDC and the World  Data
       Center  A  for  Solid  Earth Geophysics  (colocated  in  Boulder,
       Colorado).   The  data  are on the CD-ROM  in  the  International
       Organization for Standardization (ISO) 9660 format.

       Handle  the CD-ROM carefully to avoid damage.   Dust,  scratches,
       ink, paint, and fingerprints may obscure some of the data.  Given
       careful handling,  one can expect at least a 10-year lifetime for
       the data disc.

       LOADING ACCESS SOFTWARE

       The  access software is provided on  high-density (1.2  megabyte)
       5.25"  floppy  diskettes or  high-density (1.44  megabyte)   3.5"
       diskettes.   Installation instructions can be found in the README
       file on the diskettes, and are outlined below:

        1.Create a subdirectory to hold the access software (e.g., MKDIR
       C:\GNA).

        2.Change your directory to the newly created subdirectory (e.g.,
       CD C:\GNA).

        3.Insert  the access software diskette into the  diskette  drive
       (e.g., drive "A").
        4.Copy  all  the  diskette files to the hard  disk  (e.g.,  COPY
       A:\*.*).

                                       6



        5.Remove the diskette from the diskette drive.

        6.Repeat  steps 3 - 5 if you received the software on more  than
       one diskette.

        7.Add the directory name that you created in step 1 to your  DOS
       search  path.   This  will require you to edit your  AUTOEXEC.BAT
       file  or other .BAT file where you store your search  path.   The
       new  directory  name may be inserted anywhere in  the  path,  but
       normally at the end (e.g., C:\; C:\DOS; C:\BIN; .....; C:\GNA).

        8.Be sure that all CD-ROM reader software (provided with the  CD
       reader)  is  loaded into the directory you created in step  2  or
       another  directory  on  the PC's DOS search path.   This  can  be
       either Reference Technology's "STDFMAN" or a Microsoft  extension
       to  DOS.   The CD-ROM can then be accessed from any directory  or
       subdirectory on your PC's hard disk.

       WARNING:   STDFMAN may crash if Terminate and Stay Resident (TSR)
       utilities are loaded first (e.g.,  WindowDOS).  The error message
       may  say  "FLOATING  POINT  NOT  LOADED."   Call   STDFMAN   from
       AUTOEXEC.BAT before anything else gets loaded.

        9.Place  the CD-ROM (picture side up) into the reader unit,  and
       turn the unit on.

       10.Power up your PC.   From your AUTOEXEC.BAT file,  the  command
       STDFMAN (if this was used) will execute the standard file manager
       program.   [Note:  The drive should not be opened when the "busy"
       light is on.]

       The  Geophysics of North America software uses drive letter   "L"
       by default.   You may specify a different drive letter by setting
       the  DOS  environmental variable CDROMDRIVE before executing  the
       program.  For example, to use drive "P" enter SET CDROMDRIVE=P.

       11.It  is  recommended  that  you execute  the  software  from  a
       separate  "data" directory (other than the directory  created  in
       step 1 that contains the access software).   This will facilitate
       maintenance  of software and output files.   To begin  execution,
       enter the command GNA.

       12.The  CD-ROM can also be a direct data source.   Some users may
       choose  to create their own access programs in order to  use  the
       few  parameters  on the CD that are not accessed by the  standard
       programs  provided.   While some DOS commands work on the  CD-ROM
       drive and its contents, a few do not (e.g., DEL or WRITE).   This
       is explained in documentation supplied with the CD-ROM drive.







                                       7


       While at the DOS prompt,  you may change drives to the CD-ROM  by
       entering " L:  ".  Entering DIR causes the monitor to display the
       subdirectories  into  which the compact disc  is  divided.   Each
       contains further subdirectories as well.   Refer to the directory
       structure  in  Chapter  3,  Technical  Specifications,  for  more
       information.

       The  access  software serves two primary purposes  -- to  support
       data  retrieval  from the compact disc and to provide a  facility
       for a graphic "quick-look" at the data.   The retrieval  software
       emphasizes  extracts  of  latitude,  longitude,  and  geophysical
       parameters.   The  quick-look facility emphasizes screen displays
       of  data  images  (e.g.,   color  raster  representations),  data
       contours, cross sections, and value postings.

       Data  supporting the display software are generally derived  data
       sets,  stored  in  binary files on the  disc.   These  data  were
       developed  for  quick-look  display and should not  be  used  for
       rigorous numerical analyses.   Such work should be performed only
       on the archival data which are stored in an ASCII format.

       The access software will be periodically updated;  therefore, the
       user  should  reference  all inquiries to  the  specific  release
       version  number which appears in the title,  screen,  and on  the
       software diskette.



       RUNNING THE TUTORIAL

       If  you are a first time user of the Geophysics of North  America
       data base,  it is recommended that you schedule 10 minutes to run
       the tutorial provided.   This will provide a good overview to the
       protocols used throughout the product.

       The  tutorial is passive.   The user is not interacting with  the
       access software.   The  only  choices are  screen forward, screen
       backward,  or end the tutorial.   To go forward, press almost any
       key;  to go backward, press the PageUp key; to end, press the End
       key.


       FOR ADDITIONAL HELP

       If  you have technical questions about the data base,  the access
       software,  or equipment used with the disc,   please contact John
       O.  Kinsfather [303-497-6404] or Carl Abston [303-497-6276].  The
       NGDC address is:   National Geophysical Data Center,  NOAA,  Code
       E/GC1, 325 Broadway, Boulder, Colorado 80303, USA.


       Release 1.1User Instructions




                                       8


       User Instructions

       INTRODUCTION

       Each time you use the Geophysics of North America  software,  you
       create  a  color  (raster) display,  plotted and  mapped  on  the
       computer screen using VIEW DATA (IN EGA GRAPHICS MODE).   You can
       choose a data set from the menu, or from a previously saved file.

       Once you have chosen a data set,  you can display it as is, using
       default settings that are built into the software.   Or,  you can
       further  refine  the scope of the display as well as  the  colors
       used in it.

       Then,  if you wish, you can add overlays of contours, boundaries,
       and point data to the display.   The image(s) that you create can
       be  stored  to disk (or diskette) for display at a later time  or
       for creating your own computerized slide show.

       In  a  nutshell,  these  are  the things  you  can  do  with  the
       Geophysics of North America data base.   The rest of this chapter
       tells you how to do them.

       A   more  extensive  version  of  Geophysics  of  North   America
       (available  from NOAA) contains additional grids and capabilities
       to OUTPUT DATA from CD-ROM to disk.

       The  instructions are given in the order in which most users  are
       likely to proceed.   It is possible to learn to use the  software
       simply  by working your way through this User Instruction portion
       of  the  documentation,  preferably  with a  system  running  the
       Geophysics of North America data base in front of you.

       You are strongly encouraged,  however, to take the tutorial which
       comes  with the software.   You are also reminded that F1 is  the
       key to press for on-line, context-sensitive help.

       Before  you begin the step-by-step instruction,  you may want  to
       take  a  moment  to  examine  the  following  list  of   keyboard
       protocols:

       Cursor  KeysCursor keys are the keys with up,  down,  right,  and
       left  arrows on them.   You can use these to scroll  through  the
       menu and highlight each item.

       ENTERSelect highlighted item by pressing the ENTER key.

       ESCEscape.   Exit  menu  and  return to a  previously  requested,
       higher-level  menu.   If  used  during the  creation  of  a  data
       display, it will interrupt the data being plotted.

       F1View context-sensitive HELP screens.

       F2Re-display  options.   Used  when changing previously  selected
       options.

                                       9


       F3When displaying an image, produces a colored scale.

       F10Complete a process.



       LEARNING THE MENU STRUCTURE

       You will need to refer to Chapter 1, Getting Started, to find out
       how  to  set  up  your computer and  CD  reader  to  provide  the
       necessary CD-ROM environment.

       Once  the  parts of your system are connected and  Geophysics  of
       North America data base has been installed,  you can begin to use
       the software by typing the word  GNA  at the DOS prompt, and then
       pressing ENTER.

       [The DOS prompt is the symbol that indicates that your computer's
       operating  system is waiting for your instructions.  It may  look
       like this:  C> ]

       The first thing you will see on your screen is the program title,
       Geophysics of North America, and an instruction to type I to view
       the Introduction, or any other letter to begin using the program.

       The  Introduction explains the types of documentation  available,
       and where to find them.   Detailed information on how to view the
       CD-ROM  ".DOC" files,  physically located on the CD-ROM,  can  be
       obtained by pressing F1 at this point.   These .DOC files provide
       technical documentation about each of the data files.

       The Introduction also provides background information on the data
       collection  and  preparation,  and  credits the  individuals  and
       organizations  responsible  for developing  Geophysics  of  North
       America.

       Menu Structure Overview

       The software has a series of on-screen "menus" which allow you to
       choose among the available options as you use the software.   The
       diagram  on  the  following  page  illustrates  the  hierarchical
       organization represented by the various menus.


       The Main Menu

       After you view the introduction,  the first thing you will see on
       the screen is the Main Menu.

       When  an  item in a menu is highlighted by appearing  in  inverse
       video,  it  means  that this item will be selected if  you  press
       ENTER.   Typically,  when a menu first appears on the screen, the
       first  item  in  it is highlighted.   Thus,  when the  Main  Menu
       appears on the screen, the first item, VIEW DATA (IN EGA GRAPHICS
       MODE), appears highlighted.

                                      10


       You  can  choose another item by using the arrow  keys.   If  you
       press  the  down  arrow  key  once,  RUN  TUTORIAL  now  will  be
       highlighted in inverse video.  You also can use the arrow keys to
       highlight RUN UTILITIES or EXIT.

       While it is always possible to use arrow keys to highlight a menu
       item,  it is also possible simply to type the first letter of the
       item.   This will take you to the item and invoke it,  all in one
       step.   If  two  or more menu items begin with the  same  letter,
       typing that letter will select the first.

       A line at the bottom of the screen also keeps track of which item
       will be selected if you press ENTER, and reminds you that you can
       choose another item by using the arrow keys.  This Status Line is
       a regular feature of each menu in the program.

       In  addition  to  the Status Line  itself,  there  will  also  be
       reminders  about  which key to press if you need help  (F1),  and
       other useful information.   When in doubt, check the Status Line.
       It will often tell you exactly what you need to do to continue.


       DATA DISPLAY

       If  you select VIEW DATA (IN EGA GRAPHICS MODE),  the  View  Menu
       will  appear  on the screen.   The View Menu gives you access  to
       each of the major options for constructing a display image.   For
       now,  you only need to know that the item IMAGE on the View  Menu
       will  be highlighted,  and you can press ENTER to move on to  the
       Image  Selection Menu.   This menu lists all of the data  display
       (raster) sets that come with the Geophysics of North America data
       base.

       It  is  not required that you choose a data display set  at  this
       point.   If  you  wish,  you can press ESC to return to the  View
       Menu,  where  you  may decide upon other  parameters  before  you
       select an image data set.   For more predictable display results,
       however, our advice is to make your data set selection first.

       You may select one set.  The sets include:

       Topography (North America)
       Topography (United States - land/coast)
       DNAG Magnetics (DNAG = Decade of North American Geology)
       MAGSAT  Magnetics   (MAGnetics  measured  by  SATellite:   NASA's
       satellite  project to measure the near-Earth magnetic field on  a
       global basis)
       DNAG Gravity
       Isostatic Gravity (isostatic residual gravity grid for the United
       States only, using an Airy-Heiskanen model)
       Satellite Imagery, Summer
       Satellite Imagery, Fall
       (For  the  satellite imagery,  also choose  a  type:   vegetation
       index, visible, reflected infrared, thermal infrared)
       User File

                                      11


       Note:   Other  types  of  data  can be displayed  as  POINT  DATA
       (described later in this chapter).

       Detailed  information on the history of the data compilation  for
       each  of  these  data sets can be found in the  History  of  Data
       Compilation  and  Data Preparation Techniques  chapters  of  this
       manual.  Short  descriptions  of each are available on  the  help
       screen for this menu.  Press F1.

       To  make  your selection,  move through the list of data  display
       sets using the up and down arrow keys.  When you have highlighted
       the one you want, press ENTER.

       To display a "User File", the data must be in a format compatible
       with the Geophysics of North America access software.  A software
       utility  is  provided  which assists  users  in  developing  such
       formats.   For  additional information see "Running Utilities" in
       the Technical Specifications chapter of this manual.

       Whenever you return to the Image Selection Menu,  the choice  you
       made  will be highlighted,  indicating to you which data  display
       set you are presently using.   You may select only one image data
       set per data display session.  Other data sets may be overlaid as
       contours (see description in Contours section of this chapter).

       Default Color Palettes

       Each  data display set has already been prepared for display with
       a default color code or "palette" and a default area (the  entire
       data set).

       After you've made your data set selection, palette choices appear
       on  the  screen.   You can accept the system default  palette  or
       create  a new palette.   If you wish,  you can create a  "custom"
       palette  for temporary use or save it as a USER DEFAULT,  so that
       in  the future whenever you choose the user default  palette  you
       will be using your own custom palette.

       If  you choose a default palette (system or user),  the View Menu
       will  reappear.   This is the menu you will use most in  creating
       your  data displays.   If you choose to create a new  palette,  a
       Palette  Selection chart will appear (explained in detail  below,
       under "Changing the Palette").  Then, once you have repainted the
       palette, the View Menu will appear.

       The  View Menu allows you to make a number of additions  to  your
       display,  to  return  to the Image Selection Menu,  to  exit  the
       program,  or  to display the data.   Before you make use of these
       functions,  however,  you may want to delimit the area within the
       data set that you wish to display.  To do this, you should select
       the AREA option on the View Menu.





                                      12


       If  you choose to select a NEW area,  you will delimit  the  area
       using  one of two methods.   These are discussed in detail below,
       under "Changing the Area".  Or you may choose the entire data set
       by selecting ALL.

       You  can display the data set immediately from the View  Menu  by
       choosing GO.  Select GO by typing  G .  Or, you can use the arrow
       keys to highlight the word GO, and then press ENTER.

       The  image  will be drawn on the screen.   To return to the  View
       Menu and continue layering the display with boundaries, contours,
       and point data, just press the ENTER key or F10.


       Summary

       In order to display an image,  you must select (1) data set,  (2)
       palette,  and  (3) area.   If the default values for palette  and
       area  are satisfactory for your purposes,  you can  select  them,
       select  GO,  and see the image on-screen.   If not,  the  program
       allows  you to re-define either one,  or both,  of these  values.
       The  next  two sections describe how to design a new palette  and
       how to define a new area.


       Changing the Palette

       After you have selected your image,  the Palette Menu will appear
       on  the screen.   Select NEW.   The EGA COLOR  PALETTE  SELECTION
       screen will appear.

       On  the left side of the screen,  you'll see a color bar  showing
       the  default  values for each color distributed over the  extreme
       range  of the selected data set.   In the middle will be  another
       color bar showing available EGA colors with a number assigned  to
       each  one.  To  the right of this color chart is a  scaled  chart
       showing the current data intervals and the color for each.  If an
       image  has  been  previously viewed,  a data  distribution  plot,
       unique for the area chosen,  will appear.  This data distribution
       plot is very helpful to the user;  therefore,  it is  recommended
       that  you  always view the area with the default  palette  before
       changing  colors.   Instructions  on  how to change  the  current
       palette,  and on how to save your changes,  appear at the top  of
       the screen in a HELP window.   Press the F1 key to toggle between
       the HELP windows.

       Notice the arrow pointing to the bottom of the data interval bar.
       The up and down arrows move this marker to allow you to designate
       colors  for your own specified data value intervals.   Use the up
       arrow  to establish your first color interval.   Notice that  the
       corresponding data value appears to the left of the marker as  it
       moves  up  and  down.   You  may change  the  arrow  speed  (step
       interval) by pressing the + (fast) or - (slow) keys.



                                      13


       Anchor the marker at the top of the interval by pressing ENTER.

       Now  type  the  number  of  the color you want  to  use  in  this
       interval,  and  press ENTER again.   The color you have  selected
       will  appear  in the distribution plot,  from the bottom  to  the
       point you have just fixed.

       Move  the marker up the distribution plot to the top of the  next
       interval,  anchor the marker,  type the number of the next color,
       and press ENTER.   Continue this process until you have  selected
       colors for the entire palette chart.

       A  quick  way to alter colors in an area of interest that  has  a
       small  range of colors is to use a color stretch  technique.   To
       rapidly stretch the 15 colors into the range of your data,  press
       the "Insert" key during your "NEW" palette session.

       If   you  have  selected  a  palette  which  you  expect  to  use
       repeatedly,  you may save it as a custom "user default"  palette,
       to  be substituted for the software's default palette.   To  save
       your  new palette,  and return to the View Menu,  press the "End"
       key.

       If you did not save a user default palette, press F10 to indicate
       that you are done.   The View Menu will appear on the screen,  so
       that you can make your selection regarding AREA.


       Summary

       To change the palette,  select NEW at the Image Selection  screen
       palette  menu.   Then define the intervals and the color for each
       interval.   Save  the palette,  if you wish,  as a  user  default
       palette for future use.  Press F10 to indicate that you are done.


       Changing the Area

       After  selecting  option AREA (from the View Menu),  a menu  will
       appear with two choices, NEW and ALL.  If you do not wish to view
       the  entire  data set,  you may change the default  settings  for
       AREA.   Select NEW.   Then you may choose the WINDOW IMAGE method
       or the ENTER LIMITS method of defining the area,  by highlighting
       the one you want and pressing ENTER.

       If  you  select ENTER LIMITS,  type in the values for  upper  and
       lower latitude,  right and left longitude,  pressing ENTER  after
       you type each one.  The maximum area limits containing data are 0
       to  90  degrees  N latitude,  and 170 degrees E to 10  degrees  W
       longitude.

       If, instead, you select WINDOW IMAGE, a map will appear on screen
       with  the "window" (a rectangle shape) superimposed on  it.   You
       may  move the window to a different location on the  map,  change
       its proportions,  and/or enlarge or decrease its size.

                                      14


       The  area enclosed by your completed window will be the new  area
       displayed on the screen.

       There  are some important technical features of the WINDOW IMAGES
       which deserve explanation:

       1.If a display image is selected prior to defining an area  (this
       is  the  recommended procedure),  the background image will be  a
       display  of  that data set.   It will present the window  in  the
       exact  dimensions that will fill a screen,  with one color  pixel
       representing  each  grid  value of that  data  set.   Choosing  a
       smaller  area  will cause the image to fill an area less  than  a
       whole  screen.    Using  a  larger  area  will  result  in   data
       decimation, and will require more time to draw the picture.

       2.If a display image is not selected prior to defining an area, a
       generic  coastline  boundary appears on the screen with a  select
       rectangle  containing dimensions of 29 degrees latitude  by  53.3
       degrees  longitude.   This window size will produce a full-screen
       image for any data type other than satellite imagery  (decimating
       all  data sets other than 5-minute topography).   A smaller  size
       may fill less than a full screen, depending on the data type.

       The  various keys used for these manipulations of the window  are
       given  in a HELP menu that you can call to the screen by pressing
       F1.  These are:


         Key  Action

       (box movements)Up ArrowMove North
       Left ArrowMove West
       Right ArrowMove East
       Down ArrowMove South

       (box size)tShrink top
       bShrink bottom
       lShrink left
       rShrink right
       TGrow top
       BGrow bottom
       LGrow left
       RGrow right

       (other)PgUpIncrease box size in all directions
       PgDnDecrease box size in all directions
       -Decrease action step size
       +Increase action step size
       F10Select current coordinates and exit
       EscExit this help screen


       Once the window size and location meets your requirements,  press
       the ENTER key or F10 to indicate you are done.


                                      15


       Summary

       At  the  View Image screen,  select AREA.   To change  the  area,
       select NEW.  Then select either WINDOW IMAGE or ENTER LIMITS.  If
       you  select WINDOW IMAGE,  position the window where you want  it
       and  determine  its size and proportions.   If you  select  ENTER
       LIMITS,  type in the limits you wish to set.   Press F10 or ENTER
       to indicate that you are done.


       Displaying the Image

       Once  you have accepted the default values for palette  and  area
       (or selected your own)  and returned to the View Menu by pressing
       the  ENTER key or F10,  you can select GO to display an image  of
       your data.

       Even  if you plan to add a variety of optional overlays,  you may
       want  to display the image at this point to make sure that  color
       and area look as you expect them to.   The first time you display
       an  image,  particularly if you have redefined both  palette  and
       area,  painting  it  on  the screen may take up to  two  minutes.
       Typically,  after it has been displayed once,  it will take  only
       seconds to display again.

       To add a color scale to your display,  press F3.    To remove the
       scale, press F3 again, or ESC.

       When you are finished viewing the display, press the ENTER key or
       F10 again or ESC, to return to the View Menu.  You can now add to
       the display or start a new one.   The three types of overlays are
       point data, contours, and boundaries.


       Summary

       Select  GO from the View Menu to display an image.   Press ENTER,
       F10, or ESC to return to the View Menu.


       Point Data

       POINT  DATA are lithospheric data relating to specific points  of
       occurrence.   Geophysics of North America provides point data for
       seismicity,  crustal stress, and thermal aspect.  To choose POINT
       DATA,  press  p ,  or highlight the item and press  ENTER.   Then
       choose one of the three types listed, and press ENTER again.  The
       types are EARTHQUAKES, STRESS, and THERMAL.

       To  remove all the earlier point data and start  anew,  you  also
       have the
       option of selecting CLEAR FIELDS, and then selecting POINT MENU.




                                      16


       DNAG Seismicity Data

       To  plot  seismic  (earthquake  epicenter)  point  data,   select
       EARTHQUAKES.   Select  from the Symbol Box the symbol you wish to
       use in your display to indicate earthquakes.  Symbol choices  are
       closed box, open box, closed circle, open circle, and cross.

       Select  from  the Color Chart the color you want  to  use.  Since
       colors  vary  on different monitors,  the name of each  color  is
       displayed at the bottom of your screen in that color, so that you
       can tell exactly what you are going to get.

       The  earliest  and latest dates for which data will be  displayed
       are 1534 and 1985.  You may narrow these ranges by typing a later
       minimum or earlier maximum date.  Also,  if you wish,  enter  the
       minimum  and  maximum magnitudes of earthquakes you want  plotted
       (ranging from 2.50 to 8.70).  Use ENTER to record each value.

       You may also select CLEAR FIELDS, and then select EARTHQUAKES, to
       remove all earlier earthquake point data and start  anew.  Select
       View Menu to return to that menu.

       When you have completed your selections,  you will be returned to
       the  View Menu.   Select GO to display the data.   You may repeat
       this process,  selecting a different symbol and/or color for each
       set of dates and magnitudes.


       Crustal Stress Data

       To plot crustal stress point data,  select STRESS.   Type in  the
       minimum  and maximum azimuths (from 0 to 180),  and use ENTER  to
       record each value or accept defaults.   Then select the type from
       the  list on-screen.  If you choose not to specify a type,  press
       ENTER and all types will be included.  Types include:

       ALLAll types
       BOBreakouts
       FM (A)Average of focal mechanisms
       FM (C)Composite focal mechanism
       FM (S)Single focal mechanism
       G-FSGeologic - fault slip
       G-VAGeologic - volcanic alignment dikes and cinder cones
       IS-FJIn-Situ - flat jack
       IS-HFIn-Situ - hydrofrac
       IS-OCIn-Situ - overcore
       IS-PCIn-Situ - petal center core
       MMixed indicators

       Select minimum and maximum quality in the range from A (best)  to
       D (worst) or E (unknown),  and select color to be associated with
       directional symbol.




                                      17


       You  may  also select CLEAR FIELDS,  and then select  STRESS,  to
       remove all earlier stress point data and start anew.  Select View
       Menu to return to that menu.

       When you have completed your selections,  you will be returned to
       the View Menu.  Select GO to display the data.

       You  may  repeat  this process,  selecting  different  types  and
       quality ranges.


       DNAG Thermal Aspects Data

       To  plot thermal aspects point data,  select  THERMAL.   You  may
       search  for heat flow data or thermal gradient data in a  variety
       of ways:   individually, in unique combinations, or simply as ALL
       thermal aspects data.

       Select  from  the Symbol Box the symbol you wish to use  in  your
       display  to  indicate thermal aspect.  Symbol choices are  closed
       box,  open box,  closed circle,  open circle,  and cross.  Select
       from the Color Chart the color you want to use.

       Enter  the minimum and maximum heat flow you want plotted  and/or
       the  minimum  and maximum thermal  gradients.   The  minimum  and
       maximum quality should also be entered in a range from 1 to 6 (as
       shown below).

        PublishedDataError              Description
       CodeCode+/- %


         A 01  5High quality data:   deeper than 100 m,  at least a 50 m
       linear gradient
         B 02 10Medium quality data:  deeper than 50 m; some problems
         C 03 25Low quality data:  shallow; isothermal
         G 04Geothermal system
         D 05Gradient may be useful
         X 06No hope--large scale aquifer



       You  may also select CLEAR FIELDS,  and then select  THERMAL,  to
       remove all earlier thermal aspect point data and start anew.

       When you have completed your selections,  you will be returned to
       the View Menu.  Select GO to display the data.

       You may repeat this process,  selecting a different symbol and/or
       color  for  different sets of minimum and maximum heat  flow  and
       minimum and maximum thermal gradients.





                                      18


       Summary

       To plot point data on an image,  first select POINT DATA from the
       View  Menu.   Choose from EARTHQUAKE,  STRESS,  and THERMAL point
       data.   For each, delimit parameters specific to the type as well
       as symbol and color.


       Contours

       Contour  mapping  for  topography,   magnetics,  and  gravity  is
       available.

       To  choose CONTOURS,  press c,  or highlight CONTOURS  and  press
       ENTER  on the View Menu.   A menu will appear from which you  can
       select one or more of the following types of contour overlays:

       TOPOGRAPHY
       ISOSTATIC GRAVITY
       DNAG GRAVITY
       DNAG MAGNETICS
       MAGSAT MAGNETICS

       Make  your  selections by moving through the list with the  arrow
       keys until you arrive at the overlay you want; then type Y .

       Now,  select an interval for contour plotting and a color.   Each
       of  these  selections  is made by highlighting  your  choice  and
       pressing  ENTER.   If the multiple color option  is  chosen,  the
       colors   selected   represent   negative  and   positive   values
       respectively,  with the zero datum displayed in white.   Remember
       that  the  name of each color is displayed at the bottom  of  the
       screen  in that color,  so that you can tell exactly what  colors
       will appear.

       When you have completed your selections,  you will be returned to
       the View Menu.  Select GO to display the data.


       Summary

       From the View Menu,  select CONTOURS and then select the type  of
       contour overlay desired.   Enter an interval and a color for each
       contour plot you wish to make.


       Boundaries

       To  plot  geopolitical  boundaries on  your  image,  type  b,  or
       highlight  BOUNDARIES  and  press  ENTER.   Select  one  or  more
       boundary display sets from the list that follows:





                                      19


       COASTLINE:    Coastlines   of  oceans  and  lakes,   as  well  as
       international boundaries.   Choose GENERAL (plots  quickly;  good
       for   large  displays  such  as  a  country)  or  DETAIL   (finer
       resolution).

       STATES   &  PROVINCES:    Use  this  with  COASTLINE  to  include
       international boundaries.

       U.S. COUNTIES:  Use this with STATES & PROVINCES to include state
       boundaries,   and   with  COASTLINE  to   include   international
       boundaries.

       LAT\LONG GRID:  Choose specific grid color and interval.

       To  display  a  grid overlay while viewing  the  image,  use  the
       special  feature CTRL-G.   This capability is described later  in
       this  chapter (see the section on Special Features).   Make  your
       display  selections  by  highlighting  the  items  you  want  and
       pressing Y after each.

       Choose the color in which you want the boundary displayed and, in
       the  case of the latitude/longitude grid,  the number of  degrees
       between lines of latitude and lines of longitude.   When you have
       completed your selections, you will be returned to the View Menu.
       Select GO to display the data.


       Summary

       To plot geopolitical boundaries,  select BOUNDARIES from the View
       Menu.    Then  choose  one  or  more  boundary  sets.    For  the
       latitude/longitude grid, also enter the desired interval.  Select
       the color for each boundary set.


       Saving and Restoring an Image

       Once you have created a satisfactory image,  you may wish to save
       it in a data file so that you may recall it to the screen at some
       future  date  without needing to reconstruct it.   To  save  your
       screen return to the View Menu.

       Select  SCREEN,  and then select SAVE.   You will be prompted  to
       provide  a file name.   Type in the file name,  and press  ENTER.
       The last image that you displayed on the screen will be saved.

       SCREEN provides several other functions:

       To  retrieve  an  image that you have  previously  saved,  select
       SCREEN,  and then select RESTORE.   You will be prompted for  the
       name  of  the  file you wish to restore.   Type it in  and  press
       ENTER.




                                      20


       Select SCREEN, and then select TITLE to give a title to the image
       most  recently  displayed.   Type in the title  you  want;  press
       ENTER.

       Select  GO and the image will be redisplayed with the  title  you
       have chosen.   If you save an image with a title,  the title will
       be  saved  with  it and will appear when you restore  the  image.
       Titles created using this technique can not be erased;  they  can
       only be changed.   Another technique,  which produces an erasable
       pre-defined  title,  is the CTRL-T function (described in Special
       Features below).

       Select  SCREEN,  and  then select CLEAR SCREEN to erase  all  the
       parameters that you have selected during the session, and begin a
       new session.

       Finally,  you may select VIEW MENU to leave the SCREEN option and
       return to the View Menu.


       Summary

       To title,  save, or restore an image, select SCREEN from the View
       Menu.  SCREEN may also be used to clear the screen.


       Special Features

       Escape and Soft Abort

       While  using  this software package,  you may quit what  you  are
       doing at any time by pressing the ESC (Escape) key, which returns
       you to your previous screen or previous menu item.

       Often  the ESC option is listed in the STATUS LINE at the  bottom
       of  your  screen,  along with a short explanation  of  what  will
       happen when you choose it.  You can also use it to abort an image
       that is presently on-screen.

       It  can take a few minutes for some images to be drawn on-screen.
       If  you decide after just a few seconds that what is being  drawn
       isn't what you want,  you don't have to wait for the whole  image
       to be drawn.  You can abort the image by pressing ESC.  This will
       stop  the  current data layer from being drawn and return you  to
       the next data layer or the menu for a new selection,  leaving  in
       place  all  of  the earlier choices you have made.   If  you  are
       trying  to escape from a multiple layer display,  you must  press
       ESC once for each layer.








                                      21


       CTRL-V -- Specify Data Values at a Point

       You  may request data for a specific point on any image you  have
       created,  by  using  the CTRL-V command while that image  is  on-
       screen.   To  execute a CTRL-V,  press the Control (CTRL) key  on
       your keyboard, and while you are holding it down, press the V key
       (upper or lower case).

       A cross-hairs marker will appear in the lower left hand corner of
       the screen, which can be moved about on the image using the arrow
       keys.   The  latitude and longitude position of this  cross-hairs
       marker will also appear on the screen.   In this context, + and -
       can  be  used  to increase or decrease  the  movement  step  size
       incrementally.   When  you have located the cross-hairs marker at
       the point for which you wish to obtain data,  press ENTER.  A box
       will  appear  on-screen,   giving  the  data  values   (latitude,
       longitude,  topography, magnetics, and gravity) for the point you
       selected.

       Press  ESC  or  ENTER  to exit the CTRL-V command  and  to  erase
       values.


       CTRL-P -- Create a Data Profile

       When  viewing an image,  you may request a data cross-section  by
       pressing CTRL-P.   To execute a CTRL-P,  press the Control (CTRL)
       key on your keyboard,  and while you are holding it  down,  press
       the  P  key  (upper or lower case).   A cross-hairs  marker  will
       appear on-screen,  which you can move using the arrow keys.   The
       latitude  and longitude position of this cross-hairs marker  will
       also  appear  on the screen.   The + and - keys can  be  used  to
       increase  or decrease the step sizes in this process.   When  you
       have  located  it on the first point of the line  delimiting  the
       cross-section,  press  ENTER.   Then move it to the second point,
       press ENTER again, and a profile of the image will appear.

       Information  that  accompanies  the  profile  includes:  (1)  the
       latitude and longitude positions of the end points, (2) the title
       of  the  data  type (with units of  measure),  and  (3)  a  scale
       identifying the highest and lowest values along the profile.

       To change the vertical scale,  use the PAGE DOWN or PAGE UP keys.
       To  change the color of the profile,  use the + and  - keys.   To
       compare this profile with profiles of other data types one enters
       a data type code.   To view the choices of data type codes, press
       F1  and then enter the code desired.

       To  save  a  profile,  press CTRL-S.   Enter a name (of up  to  8
       characters and no extension) and then press ENTER.   The  profile
       image  will  be  saved as your file name with a  ".BMP"  (bitmap)
       extension.

       Press ESC or ENTER to exit the CTRL-P command.


                                      22


       CTRL-G -- Create Grid

       You  may add a grid to and remove a grid from an on-screen  image
       by   pressing  the  CONTROL  key  and  the  letter   G   (CTRL-G)
       simultaneously.   Prior to using this feature,  the grid size and
       colors  must be specified within the BOUNDARY selection option of
       the View Menu.  Type CTRL-G a second time to remove the grid.


       CTRL-T -- Display a Title for Screen

       By  pressing  CTRL-T,  a title will appear on  your  screen.   To
       remove this title,  press CTRL-T again.   This title differs from
       the  one  created by the SCREEN option in the View  Menu  in  two
       ways:   (1)  the user has no control over the words in the title,
       and (2) the title is erasable.


       PgUp -- Enlarge Image

       Some  combinations of requests may result in an image which  does
       not  fill the screen.   This is likely to occur if you  determine
       area before you select the data set.

       To enlarge such an image so that it more nearly fills the screen,
       press PgUp (the Page Up key).   This option increases the  number
       of  pixels used per square unit of display;  it does not increase
       the  resolution.   Put simply,  it enlarges whatever  detail  you
       already have, but it does not increase the amount of detail.  You
       can  PgUp  more than one time,  and PgDn reverses this  sequence.
       The PgUp feature enlarges up and to the right from the lower left
       hand screen corner.

       If data were decimated in the data selection procedure,  the PgUp
       feature will not work.


       F3 -- Display Color Scale

       If you press the F3 key while viewing an image,  a color bar will
       appear  which identifies the range of data values represented  by
       each color.  Pressing F3 again will remove this scale.



       DATA UTILITIES


       There  are two stand-alone utilities for the Geophysics of  North
       America  (GNA)  data  base.   These utilities may  help  you  (1)
       produce  a PC-style slide show of saved images or (2)  convert  a
       user  file into a format compatible with the GNA Access Software.
       In the future,  users of our access software may contribute their
       own utilities.  To learn more about available utilities, refer to


                                      23



       Release 1.1Technical Specifications


       Technical Specifications


       DATA FORMATS ON THE COMPACT DISC

       Details  of the specific format of each data file are located  in
       fifteen  separate  .DOC files written on the  compact  disc.   To
       learn   how   to  view  these  documentation   files,   run   the
       "Introduction"  from  the title screen and press F1  for  on-line
       help.   You  may  find it appropriate to have a printout  of  the
       documentation as you work with the files.



       DIRECTORY STRUCTURE OF THE COMPACT DISC

       The  directory structure of the compact disc is outlined  on  the
       following   pages.   For  a  more  detailed  description  of  the
       directory, see Appendix A.


       1.ARCHIVE

       1.1GRAV

       1.1.1DNAGGRAV6-km gravity grid of N. America
       1.1.2ISOSTAT.REG8-km isostatic gravity grid of U.S.
       1.1.3ISOSTAT.RES4-km isostatic residual grid of U.S.
       1.1.4ISOSTAT.TOP8-km isostatic topography grid of U.S.
       1.1.5SEGGRAV4-km gravity grid of U.S.


       1.2MAG

       1.2.1MAGSAT22-deg satellite magnetic grid
       1.2.2DNAGMAG.GRD2-km magnetic anomaly grid of N. America

       1.3POINT

       1.3.1SEISMIC
       1.3.1.1SEISARCEarthquake seismicity data
       1.3.1.NEQARC.NNRegionalized earthquake seismic data (32 files)
       1.3.2STRESSCrustal stress data
       1.3.3THERMALThermal aspects data


       1.4TOPO

       1.4.1ETOPO55-min topographic grid of N. America
       1.4.2NOSATL30-sec bathymetric grid of U.S. - Atlantic
       1.4.3NOSGLF30-sec bathymetric grid of U.S. - Gulf of Mexico

                                      24


       1.4.4NOSGRL30-sec bathymetric grid of U.S. - Great Lakes
       1.4.5NOSPAC30-sec bathymetric grid of U.S. - Pacific
       1.4.6NOSPRR30-sec bathymetric grid of U.S. - Puerto Rico
       1.4.7TOPOEA30-sec topographic grid for eastern U.S.
       1.4.8TOPONW30-sec topographic grid for northwestern U.S.
       1.4.9TOPOSW30-sec topographic grid for southwestern U.S.
       1.4.Nnnnnnn.INXIndex files (8) for 30-sec data retrievals



       2.IMAGE

       2.1BOUNDARY

       2.1.1COASTHI
       2.1.1.1COASTHI.INXHigh-resolution coastline index file
       2.1.1.NCOASTHI.NN41 regionalized high-resolution  coastline files

       2.1.2COASTLO
       2.1.2.1COASTLO.INXLow-resolution coastline index file
       2.1.2.NCOASTLO.NN6 regionalized low-resolution coastline files

       2.1.3COUNTY
       2.1.3.1COUNTY.INXCounty boundary index file
       2.1.3.NCOUNTY.NN37 regionalized county boundary files

       2.1.4STATE
       2.1.4.1STATE.INXState boundary index file
       2.1.4.NSTATE.NN7 regionalized state boundary files


       2.2CONTOUR

       2.2.1DNAGGRAV
       2.2.1.1DGRAV.INXGravity anomaly contour index file
       2.2.1.NGRAV.NN100 regionalized gravity contour files

       2.2.2DNAGMAG
       2.2.2.1DMAG.INXMagnetic anomaly contour index file
       2.2.2.NDMAG.NNN133 regionalized magnetic contour files

       2.2.3ETOPO5
       2.2.3.1ETOPO5.INXTopography contour index file
       2.2.3.NETOPO5.NN72 regionalized topography contour files

       2.2.4ISOSTAT
       2.2.4.1IGRAV.INXIsostatic gravity contour index file
       2.2.4.NIGRAV.NN 25 regionalized isostatic gravity contour files

       2.2.5MAGSAT
       2.2.5.1MAGSAT.INXSatellite magnetic contour index file
       2.2.5.NMAGSAT.NN3 regionalized satellite magnetic contour files




                                      25


       2.3DEMOnot available in this release


       2.4POINT

       2.4.1SEISMIC
       2.4.1.NEQ.NN33 regionalized earthquake seismic display files
       2.4.2STRESSBCrustal stress display file
       2.4.3THERMALBThermal aspect display file


       2.5RASTER

       2.5.1AVHRRSatellite   data   - Advanced   Very    High-Resolution
       Radiometry (AVHRR)
       2.5.1.1JUN86.CH110-min grid AVHRR channel 1 data for June 1986
       2.5.1.2JUN86.CH210-min grid AVHRR channel 2 data for June 1986
       2.5.1.3JUN86.CH510-min grid AVHRR channel 5 data for June 1986
       2.5.1.4JUN86.NVI10-min  grid  normalized  vegetation  index  data
       (NVI) for June 1986
       2.5.1.5NOV86.CH110-min  grid  AVHRR channel 1 data  for  November
       1986
       2.5.1.6NOV86.CH210-min  grid  AVHRR channel 2 data  for  November
       1986
       2.5.1.7NOV86.CH510-min  grid  AVHRR channel 5 data  for  November
       1986
       2.5.1.8NOV86.NVI10-min grid NVI data for November 1986

       2.5.2GRAV
       2.5.2.1ISOSTATB2.5-min isostatic gravity grid for U.S.
       2.5.2.2DGRAV2.5-min gravity anomaly grid for N. America
       2.5.2.NDGRAV.NNNnot available in this release

       2.5.3MAG
       2.5.3.1MAGSATB2.5-min satellite magnetic grid (0-50 N deg)
       2.5.3.2DMAG2.5-min magnetic anomaly grid for N. America
       2.5.3.NDMAG.NNNnot available in this release

       2.5.4SUMMARY
       2.5.4.1DGRAV.ALLDecimated gravity grid of N. America
       2.5.4.2DGRAV.IMGDecimated gravity image of N. America
       2.5.4.3DMAG.ALLDecimated magnetic grid of N. America
       2.5.4.4DMAG.IMGDecimated magnetic image of N. America
       2.5.4.5ETOPO5.ALLDecimated 5-min topography grid of N. America
       2.5.4.6ETOPO5.IMGDecimated 5-min topography image of N. America
       2.5.4.7GNA_AREA.IMGDecimated area boundary image of N. America
       2.5.4.8ISOSTAT.ALLDecimated isostatic gravity grid of N. America
       2.5.4.9ISOSTAT.IMGDecimated   isostatic  gravity  image  of    N.
       America
       2.5.4.10JUN86.ALLDecimated NVI grid of N. America - summer
       2.5.4.11JUN86.IMGDecimated NVI image of N. America - summer
       2.5.4.12MAGSAT.ALLDecimated MAGSAT grid of N. America (to 50 N)
       2.5.4.13MAGSAT.IMGDecimated MAGSAT image of N. America (to 50 N)
       2.5.4.14NOV86.ALLDecimated NVI grid of N. America - late autumn
       2.5.4.15NOV86.IMGDecimated NVI image of N. America - late autumn

                                      26


       2.5.4.16TOPO30.ALLDecimated  30-sec  topographic and  bathymetric
       grid of U.S.
       2.5.4.17TOPO30.IMGDecimated  30-sec topographic  and  bathymetric
       image of U.S.


       2.5.5TOPO
       2.5.5.1ETOPO5B5-min topographic grid of N. America
       2.5.5.2TOPO3030-sec topographic and bathymetric grid of U. S.
       2.5.5.mTOPO30.mmm30-sec regionalized topographic grids (11 files)


       Release 1.1Data Preparation
       Techniques


       Data Preparation Techniques


       PHILOSOPHY OF DATA PREPARATION

       Original  data  were  altered as little as  possible  during  the
       preparation   of  archival  data  sets  for  the  original   NOAA
       Geophysics of North America CD-ROM.  These archival data sets are
       not  present  in  the JEDI disc.   Only image  data  sets,  which
       represent a regridded and lower resolution data set are included.
       The  purpose  of  developing  the Image Data  Sets  was  to  have
       compatible  grids  which  could  be  compared  to  one   another.
       Researchers  who need higher resolution are encouraged to  obtain
       the  archival  data  available on the NOAA  Geophysics  of  North
       America CD-ROM.


       GRIDDED DATA

       Topographic 30-Second Grid Data

       There  are  several 30-second topographic files on  the  original
       Geophysics  of North America CD-ROM.   Only the combined land and
       coast file is present on the JEDI CD-ROM.

       Coastal Data.  The newest topographic data set (developed by NGDC
       specifically  for  this CD-ROM  project)  contains  U.S.  coastal
       bathymetry.    These data were generated from a higher resolution
       15-second  data set,  which in turn was developed from  trackline
       data  collected by the National Ocean Service (NOS).   The format
       was  chosen  to  be  compatible with  a  similar  land  data  set
       (described  below),  with  the exception that quality codes  were
       added to each data value.

       Land Data.  The oldest 30-second file represented an average grid
       for  land  values  only.   This file was developed  by  the  U.S.
       Defense Mapping Agency and the U.S. Geological Survey.



                                      27


       One  of the historic problems of these data was the treatment  of
       coastal  values,  as  the value of "1" was used to  represent  an
       offshore  "no  data  flag".    Software,   therefore,   can   not
       distinguish  between swamp regions (e.g.,  Mississippi Delta  and
       southern Florida) and the marine environment.

       Land/Coast.   A  combined 30-second file was created to solve the
       historic offshore problem (discussed above).  To create this data
       set,  we  masked out coastal values from the land data  set,  and
       subsequently  merged  these with the  companion  coastal  values.
       Details  of these data are found on the CD-ROM in a documentation
       file called IMAGE\RASTER\TOPO\TOPO30.DOC.  Caution should be used
       when interpreting data for inland waters,  because many of  these
       regions  are on datums that are other than sea level (e.g.,  Lake
       Superior is on a 600-foot datum).

       Regridding Arrays

       The original gridded data sets were obtained from their compilers
       in  a  variety  of  spatial  reference  systems.    In  order  to
       facilitate  the comparison of these data,  a  geodetic  reference
       system was used as the most suitable common coordinate frame.
       The Brigg's minimum curvature algorithm was chosen for a gridding
       procedure  since  the  majority  of  these  data  sets  represent
       potential  field  estimates.   We used an implementation  of  the
       Briggs  algorithm written by Mike Webring of the U.S.  Geological
       Survey.   The  Webring  code allowed us to  generate  grids  from
       randomly spaced data.

       A  grid  cell dimension of 2.5 minutes of longitude and  latitude
       was used in this regridding process.   Other gridding  parameters
       were  chosen  so  that  flagged areas containing  no  data  would
       correspond to the published DNAG maps.   The 2.5 minute grid cell
       dimension led to a high degree of spatial distortion at very high
       latitudes.   Therefore,  we  decided  to truncate  the  latitude-
       longitude grids above 80 degrees North.   NOTE:   Regridding  the
       potential  field  data from kilometers on a map  projection  into
       latitude  and  longitude introduced some gradient distortions  at
       all latitudes.   We would recommend that anyone attempting to  do
       quantitative work with the potential field grids use the archival
       data  sets.   The resulting analysis could then be projected into
       latitude  and  longitude with special utilities supplied  in  the
       access software.

       DNAG Magnetics Data for North America

       The  DNAG  magnetics compilation was received  as  four  separate
       spherical  transverse Mercator grids,  corresponding to the  four
       map  sheets published by the Geological Society of America  (GSA)
       as  the  Magnetic Anomaly Map of North America.   These maps  and
       their  corresponding  grids  overlap by about  one-third  in  the
       North-South direction.  In order to simplify the recovery of sub-
       grids in the areas of overlap,  we generated a single merged grid
       from the four original grids.   It is this merged grid which  was
       placed on the CD-ROM.

                                      28



       While merging the four grids, data values in the areas of overlap
       were compared to assure proper alignment.   Subsets of the merged
       grid  in the areas of overlap  were contoured  and plotted at the
       GSA  publication  scale  and compared to the  published  maps  to
       assure  data integrity.   These 2-km data were regridded to  2.5-
       minutes.



       POINT DATA

       DNAG Seismicity Data

       The DNAG seismicity data base was constructed by Dr.  Bob Engdahl
       of  the  U.S.  Geological Survey and contains a large  amount  of
       information  about  each  earthquake  in  the  database.  A  full
       description   of  the  process  through  which  the  catalog  was
       constructed  can be found in the paper "Seismicity Map  of  North
       America  Project"  by  E.R.   Engdahl  and  W.A.   Rinehart,   in
       Neotectonics  of North America,  Centennial Special Map Volume 1,
       by D.B.  Slemmons,  E.R.  Engdahl,  D. Blackwell, and D. Schwartz
       (The Geological Society of America, Boulder, Colo., in press).

       In  order  to make it possible to read and display  the  data  as
       quickly  as  possible,  we  kept only the information  needed  to
       display the earthquakes on the screen in our data file. The files
       are  binary,  which makes it easier for a computer to read  them.
       The names of the data files are EQ.NUM where NUM is the number of
       the region covered by that file (see list below).  Each data file
       contains a 24 byte record for each event.   The numbers contained
       in each record are:

            Date: 8 bytes in days from January 1, 1980
            Latitude (East) and longitude: 4 bytes each
            Magnitude: 4 bytes
            Line Number: (long int) 4 bytes

       The magnitude listed is the one selected by Engdahl as the  best.
       The  line  number is the number of the event in a list  which  is
       sorted chronologically.

       The entire data set was regionalized into 33 regions, each with a
       limit  of  3000 events.   The boundaries and number of events  in
       each region are:

       MinimumMinimumMaximumMaximum
       LongitudeLatitudeLongitudeLatitudeNumber
       0260.413.6265.434.63023
       1244.432.0250.837.83016
       2228.432.0238.243.62996
       3260.40.0276.013.63004
       4170.051.6199.290.03004
       5170.00.0228.451.62982
       6244.437.8250.847.62985

                                      29


       7241.434.2243.436.42980
       8228.40.0260.432.02942
       9265.413.6268.016.22949
       10208.061.6210.865.22985
       11199.251.6208.060.02945
       12208.051.6218.861.62903
       13238.232.0241.436.02917
       14243.432.0244.433.82769
       15238.236.0239.651.62752
       16228.443.6238.251.62708
       17241.036.0241.437.62644
       18241.432.0243.434.22583
       19276.00.0350.090.02367
       20218.851.6276.090.02255
       21239.636.0241.051.62247
       22268.013.6276.051.62230
       23210.861.6218.872.32122
       24243.433.8244.451.61836
       25199.260.0208.090.01786
       26241.436.4243.451.61268
       27241.037.6241.451.61263
       28265.416.2268.051.6775
       29208.065.2210.890.0621
       30250.832.0260.451.6339
       31244.447.6250.851.6114
       32260.434.6265.451.664


       The  program  LISTEQ  (on the accompanying  diskette)  reads  the
       earthquake data files and outputs the data to standard output.


       Crustal Stress Data

       The  DNAG stress display file was created from stress data  which
       were obtained from Mary Lou Zoback at the U.S.  Geological Survey
       in Menlo Park.   The display file is binary.  The entire data set
       is contained in one display file.

       The name of the data display file is NASTRESS.DAT. It is a binary
       file  and each record is 14 bytes long.  The record contains  the
       following information:

       Latitude:  4 byte float
       Longitude: 4 byte float (0 to 360 positive east)
       Quality:   1 character
       Type of Measurement: 1 character

       Character                Type

       ABO=Breakouts
       BFM(A)= Average of focal mechanism
       CFM(C)=Composite focal mechanism
       DFM(S)=Single focal mechanism
       EG-FS = Geologic - fault slip

                                      30


       FG-VA= Geologic - volcanic alignment dikes and cinder cones
       GIS-FJ=In-Situ - flat jack
       HIS-HF=In-Situ - hydrofrac
       IIS-OC=In-Situ - overcore
       JIS-PC=In-Situ - petal center core
       LM=mixed indicators

       Stress  Azimuth:  2  byte  integer  (SHmax  orientation  measured
       clockwise from North)
       Line_number: 2 byte integer reference to the archive file

       The  program  LISTSTR (on the accompanying  diskette)  reads  the
       stress data file and outputs the data to standard output.


       DNAG Thermal Aspects Data

       The  DNAG thermal data display file was created from thermal data
       which were obtained from David D. Blackwell at Southern Methodist
       University  in Dallas.   The entire data set is contained in  one
       display file.

       The name of the display file is THERMALB. It is a binary file and
       each record is 20 bytes long.  The record contains the  following
       information:

       Latitude:  4 byte float
       Longitude: 4 byte float
       Thermal Gradient (Degrees C / km : 4 byte float
       Heat Flow (Heat Flow Units, milliwatts / sq meter):  4 byte float
       Quality:   1 character

       Code      Quality

       1Errors < 5%
       25% <= Errors < 10%
       310% <= Errors < 25%
       4Geothermal System, not representative of region
       5Uncertain Quality
       6No Quality Specified

       Line_number: 2 byte integer reference to the archive file

       The  program LISTTHER reads the thermal data file and outputs the
       data to standard output.


       CONTOUR DATA

       All  data contours stored on the CD-ROM were developed using  the
       National  Center  for  Atmospheric  Research  (NCAR)   Scientific
       Computing  Division's contouring package.   Source code for  this
       package  was modified in order to capture each contour "move"  or
       "draw"  instruction.


                                      31


       The  NCAR software produces a contour position solution for  each
       contour  as  it enters or exits a grid cell.   These  "move"  and
       "draw"  instructions were then mapped from the units of the  grid
       being  contoured  (spherical transverse  Mercator,  Albers  equal
       area,  etc.) into latitude and longitude using map transformation
       software.

       The  NCAR contouring package could at best contour an array  with
       dimensions  300 by 300.  It was therefore necessary to apply  the
       contouring algorithm successively to subregions of the grid  with
       dimensions less than or equal to 300 by 300 grid cells.  A driver
       program  was written which divided the grid being contoured  into
       subregions  with one column and/or row of overlap and then called
       the contouring package.  The overlap was necessary to insure that
       contours crossing adjacent subregions would join smoothly.

       The  subregions generated by this procedure imposed a  "regional"
       structure  on  the  resulting output.   An index  data  file  was
       written  for  each data set in order to take  advantage  of  this
       regionalization of the contour vector output.  This file contains
       the positional extremes for each contour level within a region, a
       record  pointer into the contour vector file,  and the number  of
       contour  coordinate  pairs  found there.   This  index  structure
       facilitates  fast  contour  lookup by  the  Geophysics  of  North
       America  access  software in a manner that is transparent to  the
       typical user.

       Vector contour files for the DNAG gravity,  5-minute  topography,
       and  U.S.  isostatic  gravity  were produced  by  contouring  the
       original  archival  grid  data  sets.  The  vector  contour  file
       generated  by  the  attempt to contour the  DNAG  magnetics  file
       overwhelmed  the  mass storage system available to us (more  than
       160  megabytes).  We decided to contour the  regridded  latitude-
       longitude  data set.   This reduced the size (and resolution)  of
       the resulting contour vector file.

       The  original MAGSAT data contains magnetic field estimates  over
       two-degree blocks of longitude and latitude.   When this file was
       contoured,  the resulting resolution was insufficient to generate
       smooth  curves when displayed at the scales typically produced by
       our  access software.   It was therefore decided  to  interpolate
       this grid at 2.5-minute intervals and contour the resulting grid.

       Note:   The  contouring  procedure created artifacts in two  data
       sets.  In the DNAG gravity and the DNAG magnetics data, the field
       was  often  sampled along a traverse or ship  track.   The  grids
       produced,  either  by  the  original compilers or by  us  in  our
       regridding,  generated solutions several grid cells  wide.   When
       these  grids are displayed as color raster images or examined  on
       the  GSA  maps,  the track data appear as narrow bands of  color-
       coded information rather than as lines.  The contouring algorithm
       often produced closures at the edges of these same bands.   These
       closures are obviously spurious since the field was only measured
       along along a traverse.   For similar reasons, care must be taken
       when examining data adjacent to areas where there is no no data.

                                      32


       GEOGRAPHIC BINNING

       An important goal of the original Geophysics of North America CD-
       ROM  project was to make available a wide variety of  geophysical
       data sets for analysis on a regional scale.  This goal determined
       the scale for which the quick-look software was  designed.   Once
       this  scale  was decided,  one could tailor aspects of  the  data
       structure  to it,  hopefully minimizing the amount of time needed
       for  the  "average" regional-scale search  and  retrieval.   This
       optimization was done for the contour,  boundary,  and earthquake
       data  using  a  geographic binning  technique  developed  at  the
       National  Geophysical  Data  Center.   The  binning  process  and
       structure is transparent to the user of our access software.


       Binning Point Data

       The  binning  scheme is most easily understood  using  earthquake
       data because they are point data and fall easily into bins.   The
       motivation  was  to develop bins which contained nearly the  same
       number  of events,  and to let the geographic characteristics  of
       the bins (locations and sizes) be determined by the  data.   This
       was  done  using  a bin-growing algorithm which  starts  at  some
       location in an array of data and successively adds cells from the
       array  until  no  more cells can be added without  exceeding  the
       limit  on the number of events in the bin.   When this  limit  is
       reached  a new bin is started.   These steps are continued  until
       the  entire  array has been binned.   The regions which  resulted
       from  application  of this technique to the earthquake  data  are
       listed  in the .DOC files in the appropriate directories  of  the
       CD-ROM.


       Binning Geopolitical Boundary Data

       The  boundary data is different from the earthquake data  because
       the basic unit of the data is a "segment", not a point.  Segments
       are  sets  of  points which are to be connected by lines  on  the
       display.  Each segment has a bounding rectangle determined by the
       minimum  and  maximum latitudes and longitudes  in  the  segment.
       These  bounding  rectangles determined the unit which was  to  be
       placed in the appropriate bin.

       The  procedure for binning the boundary data started by  counting
       the  segments which occurred in a set of general geographic  bins
       (for example, 10 x 10 degrees).  Combinations of these bins which
       equalized the number of points were then sought.   An attempt was
       also made to minimize the number of segments which overlapped the
       bin  boundaries.   These  segments were picked up at the  end  by
       specifying the last region as the entire spatial data set.






                                      33


       Binning Contour Data

       The  data  sets which were contoured at the National  Geophysical
       Data  Center  were  split into 15 x 15  degree  regions  for  the
       contouring  procedure.   These regions were used directly without
       equalization on the CD-ROM.


       Release 1.1History of   Data Compilation

       History of Data Compilation

       DECADE OF NORTH AMERICAN GEOLOGY OVERVIEW

       by
       Dr. A.R. Palmer
       Geological Society of America (GSA)

       The  Decade  of  North American Geology  (DNAG)  Project  is  the
       centerpiece  publication project for GSA's Centennial.   By 1990,
       this project will have produced:

       a  28-volume  set of syntheses on The Geology of  North  America;
       seven  major  wall-size  maps  of North America  at  a  scale  of
       1:5,000,000   showing  geology,   magnetic   anomalies,   gravity
       anomalies,  seismicity,  heat flow, stress, and neotectonics, all
       on the same computer-compatible base; six Centennial Field Guides
       providing  short texts describing 100 of the best geologic  sites
       in each of GSA's regional sections;  twenty-four  Continent/Ocean
       Transects at a scale of 1:500,000 providing geologic and tectonic
       strip maps and cross-sections,  together with related geophysical
       information, more or less evenly spaced around the margins of the
       continent  and extending from stable craton to ocean  floor;  two
       sheets   of  comparative  continental-margin  cross-sections  for
       eastern  and  western  North America at a  scale  of  1:1,000,000
       derived  from  the  transects;  and,  six  miscellaneous  topical
       volumes.   Five of these are projects of GSA's topical divisions,
       and one relates to the Continent/Ocean Transects.

       This  massive  effort  has involved participants  from  over  100
       universities,  20 provincial and state geological surveys, 23 oil
       or  mining companies or consulting forms,  18 countries,  and  23
       national agencies in the United States,  Canada,  Mexico, Central
       and  South  America,   Greenland,   and  Israel.    This  immense
       undertaking,  ultimately  involving  over  2,000  geologists  and
       geophysicists,  should  be completed by 1990 -- a fitting  climax
       for a Centennial decade.









                                      34


       Now  -- a bit of history.   The germ of the idea for the  project
       was proposed by A.W. Bally at a GSA Council meeting in 1977.  The
       following  year,   the  Canadian  Geoscience  Council  agreed  to
       collaborate  in the DNAG Project,  and the Geological  Survey  of
       Canada  agreed to integrate the nine volumes of its next  edition
       of  Geology  and  Economic  Minerals of Canada into  the  set  of
       synthesis volumes being contemplated for the entire continent and
       adjacent oceanic regions.   In 1979, the GSA Council approved the
       DNAG  project  concept and agreed to provide  startup  funds.   A
       steering  committee,  with representatives from  Canada,  Mexico,
       Central America, and the United States, met for the first time in
       January   1980  and  a  full-time  Centennial   Science   Program
       Coordinator (CSPC) was chosen.

       In January 1981, the Geological Society of America Foundation was
       created  to  hold the money that was to be raised to finance  the
       estimated  $4 million cost to GSA for the DNAG  Project.   Before
       the  end  of  the year,  the bulk of the needed  funds  had  been
       identified in pledges from most of the major oil companies.   The
       project was off and running!


       For  more  information  on  the  DNAG  project  or  any  of   its
       publications,  contact:   Allison R.  Palmer,  Centennial Science
       Program  Coordinator,  Geological Society of America,  Box  9140,
       Boulder, CO 80301, U.S.A., [phone].

       DATA COMPILATION EFFORTS


       Hundreds of individual Earth scientists contributed indirectly to
       the  NOAA  Geophysics of North America data base -- many  through
       participation  in the committees which generated the seven  wall-
       size maps mentioned by Dr.  Palmer.   Where committee members are
       known and references are available,  credits are provided in this
       user's manual and in the automated documentation accompanying the
       accession software.



       POTENTIAL FIELDS DATA


       SEG Gravity Data for the United States

       These  data  are the product of the ad hoc  Gravity  Anomaly  Map
       (GAM)   Committee,   sponsored  by  the  Society  of  Exploration
       Geophysicists (SEG) and the U.S.  Geological Survey (USGS).   The
       committee included:

       Carlos L. AikenSigmond I. HammerRobert F. McMahon
       David F. BarnesWilliam A. HannaHerbert Meyers
       Roger H. ChapmanRalph C. HolmesNorbert W. O'Hara*
       Kenneth L. CookMartin F. KaneDonald M. Scheibe
       Peter DehlingerGeorge R. KellerWilliam E. Strange

                                      35


       Craig FerrisGeorge W. LisleClaude W. Wessels
       Richard H. GodsonPaul L. Lyons*Luman E. Wilcox

       * co-chairmen

       CONTRIBUTORS:   Air   Force  Geophysical   Laboratory,   American
       Geophysical Union,  Arizona State University,  Ashland Oil, Brown
       Geophysical  Research Corporation,  California  Division of Mines
       and  Geology,  California   Institute  of   Technology,  Chevron,
       Colorado  School of Mines,  Dartmouth  College,  Defense  Mapping
       Agency Aerospace Center,  Defense Mapping Agency Hydrographic and
       Topographic Center,  East Texas State University, El Paso Natural
       Gas  Company,  EXXON,  Florida  Department of Natural  Resources,
       Geological  Survey  of Alabama,  Geophysical  Society  of  Tulsa,
       Georgia  Institute of Technology,  Gulf Research and  Development
       Corporation,  Harvard University, Hawaii Institute of Geophysics,
       Idaho  Bureau of Mines and Geology,  Illinois Geological  Survey,
       Indiana  Department  of  Conservation,  Iowa  Geological  Survey,
       Kansas  Geological  Survey,  Kentucky Geological  Survey,  Lamont
       Doherty Geophysical Observatory,  Los Alamos National Laboratory,
       Marathon Oil Company,  E.V.  McCollum and Company, Michigan State
       University,  Michigan Technological University,  National Oceanic
       and  Atmospheric Administration,  New Mexico Institute of  Mining
       and Technology,  New Mexico State University, Newmont Exploration
       Company,   North  Dakota  Geological  Survey,  Northern  Illinois
       University,  North Western University, Ohio State University, Old
       Dominion University,  Oregon State University, Pennsylvania State
       University,    Petty-Ray   Company,   Phelps-Dodge   Corporation,
       Princeton University, Purdue University, Rensselaer Polytechnical
       Institute,  Scripps Institute of Oceanography, SOHIO Oil Company,
       South Carolina Geological Survey, South Dakota Geological Survey,
       Southern  Illinois  University,  Southern  Methodist  University,
       Stanford  University,  State  University of  New  York,  Sunmark,
       Tennessee  Valley  Authority,  Texas A and  M  University,  Texas
       Technological College,  Union Oil Company, University of Arizona,
       University of California,  University of Connecticut,  University
       of  Kentucky,   University  of  Miami,  University  of  Michigan,
       University  of Nevada,  University of New Mexico,  University  of
       North Carolina,  University of Oregon, University of Puget Sound,
       University  of  South  Dakota,  University of  Texas  at  Austin,
       University  of Texas at Dallas,  University of Texas at El  Paso,
       University  of  Utah,  University of  Washington,  University  of
       Wisconsin,  University of Wyoming,  U.S.  Geological Survey, U.S.
       Naval  Oceanographic  Office,   Vanderbilt  University,  Virginia
       Department of Mineral Resources,  Virginia Polytechnic Institute,
       Washington  University,  West  Virginia Geological  and  Economic
       Survey,  West Virginia University,  Western Illinois  University,
       and Woods Hole Oceanographic Institute.

       The compilation was developed primarily from the digital files of
       the Defense Mapping Agency (DMA).   Solicitation of data resulted
       in  the  release of about 1 million land and 0.8  million  marine
       gravity  values previously contributed to DMA and members of  the
       GAM Committee.


                                      36


       The  data  were screened to eliminate redundant  and/or  spurious
       data  points.   Onshore  data consist of Bouguer gravity  anomaly
       values  computed using a rock density of  2.67  g/cc.   Offshore,
       where data are less adequately corrected for topography, free air
       gravity anomaly values were incorporated.   Datum control for the
       gravity  computations  is  based  on  the  International  Gravity
       Standardization  Net  of  1971 and the  1967  Geodetic  Reference
       System formula for theoretical gravity (International Association
       of Geodesy, 1971).





       Data from areas with substantial relief were terrain-corrected by
       the   USGS.    Terrain  corrections  were  calculated  at  radial
       distances  from station locations ranging from 0.895  km  (Hammer
       zone F) to 166.7 km (Hayford zone O) using a rock density of 2.67
       g/cc.  The National Geodetic Survey (NGS) of the National Oceanic
       and  Atmospheric  Administration  (NOAA)  made  similar  terrain-
       corrected  calculations for editorial comparison.   The corrected
       data  were  then  transformed from geodetic  coordinates  to  map
       coordinates.

       A  gridding  program  based  on  a  minimum  curvature  procedure
       produced  values at 4-km intervals,  where  non-proprietary  data
       exists, to develop a digital data set suitable for contouring and
       data  manipulation.    This  data  base,   covering  95%  of  the
       conterminous United States, provides a station distribution of at
       least  5  minutes.    The  program,   applied  through  the  USGS
       facilities,  used a search radius of 40 km to determine values at
       grid   positions  in  areas  of  sparse  data.   This   procedure
       extrapolates  the  data  out  to the  search  radius  around  the
       irregular  boundaries of the data.  Therefore,  contours based on
       extrapolated values should be used with caution.   Station values
       included  in  the digital data set were evaluated  and  computer-
       edited by DMA, USGS, and NOAA.



       Isostatic Gravity Data for the United States

       The  isostatic  residual gravity grid was developed by  the  U.S.
       Geological   Survey  using  an   Airy-Heiskanen   model.    Local
       compensation was computed with a depth of 30.0 km to the root for
       sites  with  sea level elevations and a density contrast of  0.35
       g/cm3 across the bottom of the root.

       The isostatic grid was derived from the gravity data set used  to
       prepare  the  Gravity  Anomaly Map of the  United  States  (1982)
       published  by the Society of Exploration Geophysicists,  and from
       the  5-minute North American topographic and SYNBAPS  bathymetric
       data  sets  obtained from the National Geophysical  Data  Center.
       Contour  and colored maps of the isostatic residual gravity  data
       have been published.

                                      37



       There are four United States isostatic gravity data files on  the
       CD-ROM:

       ISOSTATB   - Residual   isostatic   gravity   in   a   2.5-minute
       latitude/longitude  grid  with  values in  mgals.   This  binary-
       formatted file was developed by Richard Hansen of the Cooperative
       Institute   for  Geoscience  Data  Management  and   Applications
       (CIGMA), using the 4-km isostatic grid described below.





       ISOSTAT.RES - Residual isostatic gravity in a 4-km grid using  an
       Albers projection (central meridian = 96-degrees; base latitude =
       0-degrees)  with  values in mgals.   These ASCII for-matted  data
       were computed from the following two 8-km grid which were also in
       an  identical Albers projection.  (Note:   Isostatic  Residual  =
       Bouguer - Isostatic Regional).

       ISOSTAT.REG  - Sea level isostatic regional data in a 8-km  grid.
       These data are ASCII formatted and in units of mgals.

       ISOSTAT.TOP - Topographic data for the conterminous U.S.  in a 8-
       km grid.  These data are ASCII formatted and in units of meters.


       Isostatic Gravity References:

       Godson,  R.H.,  and Scheibe,  D.M., 1982, Description of magnetic
       tape containing conterminous U.S. gravity data in gridded format:
       U.S.  Dept.  of Commerce, National Technical Information Service,
       PB82-254798 (magnetic tape with description), 5 p.

       Jachens,  R.C.,  Simpson,  R.W., Saltus, R.W., and Blakely, R.J.,
       1985, Isostatic residual gravity anomaly map of the United States
       (exclusive   of  Alaska  and  Hawaii):    National  Oceanic   and
       Atmospheric Administration,  National Geophysical Data Center map
       on clear film, scale 1:2,500,000.

       Simpson,  R.W.,  Jachens, R.C., Blakely, R.J., 1983, AIRYROOT:  A
       Fortran  program for calculating the gravitational attraction  of
       an Airy isostatic root out to 166.7 km:   U.S.  Geological Survey
       Open-File Report 83:883, 66 p.

       Simpson,  R.W.,  Saltus,  R.W.,  Jachens, R.C., and Godson, R.H.,
       1983,  A  description  of  colored isostatic gravity maps  and  a
       topographic  map of the conterminous United States  available  as
       35-mm slides:  U.S. Geological Survey Open File Report 83-884, 16
       p.





                                      38


       Simpson,  R.W.,  Jachens,  R.C., Saltus, R.W., and Blakely, R.J.,
       1985,  Isostatic residual gravity maps,  topographic,  and first-
       vertical-derivative  gravity  maps  of  the  conterminous  United
       States:   U.S.  Geological  Survey Geophysical Investigations Map
       GP-975, scale 1:7,500,000.

       Society of Exploration Geophysicists,  1982,  Gravity anomaly map
       of the United States (exclusive of Alaska and  Hawaii):   Society
       of Exploration Geophysicists,  scale  1:2,500,000.







       DNAG Gravity Data for North America

       The gravity grid values, spaced at 6 km, were used to produce the
       DNAG   Gravity  Anomaly  Map  of  North  America   (1987;   scale
       1:5,000,000).   Considerable  caution  should be  exercised  when
       using  these  gridded  data in regions of  sparse  coverage  (for
       example,  deep  oceanic areas).   The spatial distribution of the
       original data from which the grid was generated is shown on sheet
       5 of the published map.   Note:  There are no gridded data values
       for Mexico.

       All data were transformed to map coordinates using the  spherical
       North  American  transverse  Mercator projection with  a  central
       meridian of longitude 100 degrees W, a scale factor of 0.926, and
       a  radius  of  6371.204 km.   The forward  (STMFWD)  and  inverse
       (STMINV)  projection  routines,  which  are  included  with  this
       documentation,  can be used with this data.   The user should use
       CAUTION, however, when applying this code in two specific cases:

       1.At  or near the top of the map (Longitude = 10 degrees  W,  190
       degrees  W),  double precision constants and intrinsic  functions
       may be required on some computers to yield correct results.

       2.Since  the  top  two rows of the North  American  gravity  grid
       extend  into  another hemisphere,  modifications  to  the  listed
       routines will be necessary to yield correct results.

       These  data,  representing Bouguer gravity anomalies on land  and
       free-air  gravity anomalies over the oceans,  were produced under
       the  direction  of the Committee for the Gravity Anomaly  Map  of
       North America.  This committee was chaired by J. G. Tanner of the
       Geological  Survey  of  Canada and sponsored  originally  by  the
       Society of Exploration Geophysicists and later by the  Geological
       Society  of  America and the International Gravity Commission  of
       the International Association of Geodesy.

       Members  of  the Committee for the Gravity Anomaly Map  of  North
       America included:


                                      39


       Carlos L.V. AikenWilliam F. HannaNorbert W. O'Hara
       Peter DehlingerThomas G. HildenbrandAllison R. Palmer
       Warren T. DewhurstM. Dean KleinkopfDonald M. Scheibe
       Mauricio F. George A. McCalpinRonald E. Sweeney
         de la Fuente DuchR. Kenneth McConnellJames G. Tanner*
       Valery M. GodleyHerbert MeyersLeif Thorning
       Richard H. Godson
       * chairman


       Technical aspects of data compilation, editing, and gridding were
       carried  out  by the staff of the U.S.  Geological  Survey  under
       guidelines provided by a Data Base Working Group.  This group was
       chaired by T.G. Hildenbrand, U.S. Geological Survey, and included
       the following members:   R.E. Sweeney, R.H. Godson and W.F. Hanna
       of the U.S.  Geological Survey; J.G. Tanner and R.K. McConnell of
       the  Geological Survey of Canada;  C.L.V.  Aiken,  University  of
       Texas at Dallas;  H.  Meyers,  National Geophysical Data  Center,
       National  Oceanic and Atmospheric Administration;  D.M.  Scheibe,
       Defense Mapping Agency Aerospace Center;  and  N.W.  O'Hara,  SEA
       Inc., Indialantic, Florida.

       The  data  were  compiled from about 2  million  gravity  anomaly
       values   derived   from   surface,    airborne,   and   satellite
       measurements.    For  continental  areas,   anomalies  have  been
       computed  from measurements made with static gravimeters operated
       on dry land, sea and lake bottoms, and the frozen surfaces of the
       sea  or  lakes.   Over oceanic areas,  data  were  acquired  with
       dynamic  gravimeters operated on surface ships or in helicopters.

       For  Alaska,  Chukchi Sea,  Western Beaufort Sea,  Norton  Sound,
       Caribbean Islands,  land and offshore Colombia,  eastern  Panama,
       parts  of southern Mexico,  and the Mexico-Panama Pacific margin,
       where surface data could not be readily obtained in digital form,
       contour maps provided synthetic point gravity values.

       Over  the  oceans,   up  to  about  70  degrees  North  latitude,
       satellite-derived  free-air values filled in areas where  surface
       data were either unavailable or too sparse to provide  reasonable
       definition of the gravity field.

       Computation   of   the  gravity  anomalies  was  based   on   the
       International  Gravity Standardization Net 1971 and the  Geodetic
       Reference System 1967.  Bouguer gravity anomalies were calculated
       using  a  standard crustal density of 2670 kg/m3.   The data  for
       Venezuela  and  the high-relief areas of Canada  and  the  United
       States  have  been terrain corrected.   Elsewhere,  the data  are
       generally  not terrain corrected.   The estimated rms  error  for
       land,  surface marine, and airborne data ranges from +/- 1 to +/-
       5 milligals.  Satellite data have an estimated rms error of +/- 8
       milligals.





                                      40


       Data  were  interpolated  to  a uniform grid  using  the  minimum
       curvature method.   Satellite data,  which were provided on a 15-
       minute geographic grid, were first gridded at a 24-km interval to
       remove  the short-wavelength components at higher  latitudes  and
       then combined with the surface data.   The resultant data set was
       then interpolated to a 6-km grid.

       Data  sources and the individuals or agencies responsible for the
       compilation and integrity of each source are listed below.  Where
       data  from  two or more sources overlap,  the data set  with  the
       highest  integrity has been used.   The final selection  of  data
       from  each  source  is shown by the data distribution  index  map
       which accompanies the Gravity Anomaly Map of North America.






       DNAG Gravity Data Sources and References:

       Bering Sea/Marine:
       Childs,  J.R., Magistrale, H.W., and Cooper, A.K., 1985, Free-air
       gravity anomaly map of the Bering Sea:   U.S.  Geological  Survey
       Miscellaneous Field Studies Map MF-1728, scale 1:2,500,000.


       Alaska/Marine:
       Fisher,  M.A., Childs, J.R., and Magistrale, H.W., 1982, Free-air
       gravity  map,  Norton Basin,  Alaska:   U.S.  Geological  Survey,
       Miscellaneous Field Studies Map MF-1460, scale 1:250,000.


       Alaska/Land:
       Barnes,   D.F.,  1977,  Bouguer  gravity  map  of  Alaska:   U.S.
       Geological  Survey Geophysical Investigations Map  GP-913,  scale
       1:2,500,000.


       Chukchi and Beaufort Seas/Marine:
       May,  S.D., 1985, Free-air gravity anomaly map of the Chukchi and
       Alaskan  Beaufort seas,  Arctic Ocean:   U.S.  Geological  Survey
       Miscellaneous   Investigations   Series   Map   I-1182E,    scale
       1:1,000,000.


       Greenland/Land and Marine:
       Anderson,  O.B.,  1973,  Surface-ship gravity measurements in the
       Davis Strait,  western Greenland:  Geodaetisk Instituts Skrifter,
       3. RK., v. 39.

       Blundell,  D.J., 1978, A gravity survey across the Gardar Igneous
       Province, southwest Greenland:  Journal of the Geological Society
       of London, v. 135, pp. 545-554.


                                      41


       Bull,  C.,  1955,  Values  of gravity on the inland ice in  north
       Greenland:   Meddelelser om Gronland,  v.  137, no. 1, part 3, 11
       pp.

       Forsberg,  R.,  1986,  Gravity  measurements in Jameson Land  and
       neighbouring  parts of east Greenland:   Meddelelser om Gronland,
       Geoscience, no. 15, 23 pp.

       Hoisl,  R.,  1965,  Gravimetermessungen  uber das  Gronlandisches
       Inlandseis auf einer West-Ost profil (E.G.I.G.)  1959:   Deutsche
       Geodaetische Kommission, Reihe C, Heft 85, 53 pp.

       Kejlso, E., 1958, Gravity measurements in western Greenland 1950-
       1952:  Geodaetisk Instituts Skrifter, 3. RK., v. 27, 69 pp.

       Saxov,  S.E.,  1958,  Gravity  in western Greenland:   Geodaetisk
       Instituts Skrifter, 3. RK., v. 29.


       Svejgaard,  B.,  1959, Gravity measurements in western Greenland,
       1953-1955:  Geodaetisk Instituts Skrifter, 3. RK., v. 32, 19 pp.

       Digital  data  were provided by the  Danish  Geodetic  Institute,
       Gamlehave Alle 22, DK-2920, Charlottenlund, Denmark.

       Canadian Land and Offshore/Land and Marine:
       Digital data from the National Gravity Data Base were provided by
       the  Geophysical  Data Centre,  Geophysics  Division,  Geological
       Survey of Canada, Ottawa, Canada.

       Continental U.S./Land:
       Godson,  R.H.,  and Scheibe, D.M., 1982,  Description of magnetic
       tape  containing  conterminous U.S.  gravity data  in  a  gridded
       format:    U.S.   Department   of  Commerce  National   Technical
       Information Service, PB82-254798.

       Digital  data were provided by U.S.  Geological  Survey,  Denver,
       Colorado.


       Northern Mexico/Land:
       Digital   data  were  provided  by  C.L.V.   Aiken,   Center  for
       Lithospheric Studies,  University of Texas at Dallas, and M.F. de
       la Fuente Duch, Geosciencias Applicadas SA, Mexico, D.F.


       Southern Mexico/Land:
       Digital  data were provided by M.F.  de la  Fuente,  Geosciencias
       Applicadas  SA,  Mexico,  D.F.,  Carlos L.V.  Aiken,  Center  for
       Lithospheric Studies,  University of Texas at Dallas, and M. Mena
       Jara,  Instituto  de Geofisica,  Universidad  Nacional  Autonoma,
       Mexico D.F.




                                      42


       Central America/Land:
       Digital data were provided by C.L.V.  Aiken, V.M. Godley and J.N.
       Kellogg, Hawaii Institute of Geophysics, Honolulu, Hawaii, and M.
       Zuniga, Universidad Nacional Autonoma de Honduras.


       Central and South America/Land and Marine:
       Kellogg,  J.N.,  Godley,  V.M.,  Woollard,  G.P., Ropain, C., and
       Bermudez Gomez, A., 1983, Simple Bouguer gravity map of Columbia,
       eastern Panama,  and adjacent marine areas:   Transactions of the
       10th Caribbean Geological Conference, Cartegena, Columbia.

       Kellogg, J.N., Godley, V.M., Woollard, G.P., Ropain, C., Bermudez
       Gomez,  A.,  and  Murphy,  T.,  Free-air gravity map of Columbia,
       eastern  Panama,   and  adjacent  marine  areas:    submitted  to
       Geological Society of America Map and Chart Series.

       Digital data were provided by J.N.  Kellogg,  formerly of  Hawaii
       Institute of Geophysics (HIG),  Honolulu, Hawaii and presently at
       University of South Carolina,  Columbia, South Carolina, and V.M.
       Godley, HIG, Honolulu, Hawaii.


       Venezuela/Land and Marine:
       Digital  data were provided by V.  Graterol from the  Universidad
       Simon  Bolivar (USB) gravity data base,  including the  following
       data sets:

       1.USB  gravity  surveys  in  Venezuela,   1975-1987,   containing
       collaborative projects with Direccion de Cartografia Nacional and
       Interamerican Geodetic Survey;
       2.DCN gravity surveys in Venezuela, 1950-1986;
       3.Woods Hole Oceanographic Institution gravity surveys,  offshore
       Venezuela, 1950-1960; and,
       4.Princeton  University  gravity surveys,  R.J.  Smith  and  W.E.
       Bonini, 1970-1975.


       Caribbean region/Land and Marine:
       Westbrook,  G.K.,  in press, Gravity anomaly map of the Caribbean
       region:  in Dengo,  Gabriel and Case,  J.E.,  eds., The Caribbean
       region:  Boulder,  Colorado,  Geological Society of America,  The
       Geology of North America, v. H, scale: 1:5,000,000.


       Bahamas/Land and Marine (via Helicopter):
       Helicopter  gravity  survey flown by Carson  Geoscience  Company,
       1985.

       Digital data were provided by U.S.  Department of Defense Gravity
       Library.





                                      43


       Pacific Margin and Gulf of Mexico/Marine:
       Couch,  R.W.,  Ness, G.E., Victor, L., Shanahan, S., and Troseth,
       S.C.,  1986, Free-air gravity anomalies, Southern Mexico to Costa
       Rica  margin in Ladd,  J.W.,  and  Buffler,  R.T.,  eds.,  Middle
       America    Trench   off   Western   America:     Marine   Science
       International, Ocean Drilling Program, Regional Atlas Series.

       Digital data were provided by R.W.  Couch and G.E.  Ness,  Oregon
       State University,  Corvallis,  Oregon, for Gulf of California and
       offshore Yucatan.   Other digital data from R.W.  Couch and  G.E.
       Ness  for the margins of Oregon,  Washington,  British  Columbia,
       Alaska and Mexico are included in the U.S.  Department of Defense
       Gravity Library data.


       Atlantic, Pacific and Arctic Oceans and Caribbean Sea/Marine:
       U. S. Department of Defense Gravity Library, St. Louis, Missouri.


       Open Oceans/(via Satellite):
       Balmino, G., Moynot, B., Sarrailh, M., and Vales, N., 1987, Free-
       air  gravity  anomalies  over the oceans from Seasat and  GEOS  3
       altimeter data: EOS, v. 68, no. 2, pp. 17-18.

       DNAG Magnetics Data for North America

       The magnetic data,  gridded at 2-km intervals,  were developed in
       order to produce the Magnetic Anomaly Map of North America (1987;
       scale  1:5,000,000).   Users should be aware that the  data  were
       compiled  at a grid interval appropriate for the published  scale
       and color contour intervals of 100 nanoteslas (gammas).  Attempts
       to use the data to produce larger scale maps or contour intervals
       less  than 100 nanoteslas may reveal discontinuities between some
       data sets used in compiling the map.

       All data were transformed to map coordinates using the  spherical
       North  American  transverse  Mercator projection with  a  central
       meridian of longitude 100 degrees W, a scale factor of 0.926, and
       a  radius  of  6371.204 km.   The forward  (STMFWD)  and  inverse
       (STMINV)  projection  routines,  which  are  included  with  this
       documentation,  can be used with this data.   The user should use
       CAUTION, however, when applying this code in two specific cases:

       1.At  or near the top of the map (Longitude = 10 degrees  W,  190
       degrees  W),  double precision constants and intrinsic  functions
       may be required on some computers to yield correct results.

       2.Since  the  top two rows of the North  American  magnetic  grid
       extend  into  another  hemisphere,  modifications to  the  listed
       routines will be necessary to yield correct results.


       Members  of the Committee for the Magnetic Anomaly Map  of  North
       America included:


                                      44


       William E. BoniniWilliam J. Hinze*Allison R. Palmer
       James E. CaseJames R. HeirtzlerNorman W. Peddie
       Mauricio F. Robert H. HiggsMichael S. Reford
          de la Fuente DuchPeter J. Hood*Dennis J. Teskey
       Richard H. GodsonM. Dean KleinkopfLeif Thorning
       Stuart A. HallHerbert MeyersIsidore Zietz
       William F. Hanna
       * co-chairmen

       The  final  version  of  the magnetic data was  compiled  by  the
       Aeromagnetic  Data  Processing  Section,   Geological  Survey  of
       Canada,  Ottawa, under the direction of S. Dwight Dods, Dennis J.
       Teskey,  and Peter J. Hood from original ship-track data, flight-
       line data,  gridded data, and compiled regional maps.  Sources of
       these  data  are shown on the data distribution index  map  which
       accompanies the Magnetic Anomaly Map of North America.   However,
       as  some  of these sources represent compiled  maps  and  gridded
       data,  it  is  not possible to acknowledge all original  sources.
       Those interested in the original sources should view the list  of
       data sources for further information.




       The  magnetic  map was compiled using a nucleus of data from  the
       conterminous  United States,  Canada,  and Alaska.   Each of  the
       three  data  sets forming the nucleus was  prepared  individually
       using the new Definitive Geomagnetic Reference Field (DGRF),  and
       the  original  join  between them was remarkably  free  of  major
       discrepancies.   Adjustments  to  this  nucleus  were  necessary,
       however,  in the northeast corner of the United States, where the
       United  States  data were tilted 70 nanoteslas to match  the  New
       Brunswick data and the newly-acquired Canadian offshore data, and
       in  the  panhandle area of Alaska,  where the data  were  lowered
       approximately 150 nanoteslas.

       The   extensive   ship-track  data  provided  by   the   National
       Geophysical Data Center were also corrected using the DGRF.  Even
       though  they were not extensively edited or leveled,  except  for
       obvious  erroneous  tracks,  the data merged very well  with  the
       nucleus;    however,   discrepancies   remain   at   some   track
       intersections.  These ship-track data and the nucleus then served
       as a basis for making necessary adjustments to other data sets.

       Control lines flown by the Geological Survey of Canada were  used
       to  resolve leveling problems in the area south of James Bay  and
       to verify data levels in the Caribbean region.


       DNAG Magnetic Data References and Sources:






                                      45


       North Atlantic Ocean:
       Roberts,  I.G.,  and Jones, M.T., 1980, Magnetic anomalies in the
       north
       east   Atlantic:    United  Kingdom  Institute  of  Oceanographic
       Sciences.

       Walzak, J.E., 1963, A marine  magnetic survey of the  New England
       Seamount Chain:  U.S. Naval Oceanographic Office Report TR-159.

       Digital  data were provided by U.S.  Naval Oceanographic  Office,
       Bay St. Louis, Miss.;  U.S. Geological Survey, Denver, Colo.; and
       United Kingdom Institute of Oceanographic Sciences.


       Iceland:
       Digital data were provided by U.S. Naval Research Laboratory.


       Greenland:
       Digital data were provided by Gronlands Geologiske  Undersogelse,
       Greenland.



       Gulf of Mexico and Caribbean Sea Area:
       Bracy,  D.P., 1968, Structural implications of magnetic anomalies
       north of the Bahama-Antilles Islands:  Geophysics, v. 33, p. 950-
       961.

       Hall, S.A., Shepherd, A.V., Titus, M.W., and Snow, R.L. (east  of
       90 degrees), Pilger, R.H., Rubin, D.S., and Kauth, L.M. (west  of
       90 degrees),  1984,   Magnetic total anomalies in Buffler,  R.T.,
       Locker,  S.D.,  Bryant,  W.R.,  Hall, S.A., and Pilger Jr., R.H.,
       eds.,  Gulf  of Mexico:   Ocean Margin Drilling Program  Regional
       Atlas 6, Marine Science International, Woods Hole, Mass.

       Hall,  S.A.,  and Westbrook, G.K., in press, Magnetic anomaly map
       of the Caribbean region, in Dengo, Gabriel, and Case, J.E., eds.,
       The Caribbean Region:  Geological Society of America, Volume H of
       the Geology of North America, Boulder, Colo.

       Westbrook,  G.K.,  1984,  Magnetic  total intensity anomalies  in
       Lesser  Antilles  in  Arc and Adjacent  Terranes:   Ocean  Margin
       Drilling Program Regional Atlas 10, Marine Science International,
       Woods Hole, Mass., p. 4.

       Digital  data  were provided by British  Royal  Navy,  Geological
       Survey of Canada, Lamont-Doherty Geological Observatory, National
       Oceanic   and  Atmospheric   Administration,   Petroleum   Office
       Belmokan,  U.S.  Geological  Survey,  U.S.  Navy,  University  of
       Houston, and Woods Hole Oceanographic Institution.





                                      46


       Pacific Ocean:
       Atlas Geofisico De La Margin,  Continental Oeste,  Mexico, 22-deg
       to 32-deg Lat. Norte, 1980, Direccion General De Oceanografia, SM
       No. 14a. Secretaria De Marina, Estados Unidos Mexicanos.

       Ladd,  J.W.,  and Buffler, B.T., eds., 1985, Total field magnetic
       intensity anomalies,  in Southern Mexico and Guatemala Margin, in
       Middle America Trench off Western Central America:  Ocean  Margin
       Drilling Program Regional Atlas 7,  Marine Science International,
       Woods Hole, Mass.

       Mason,  R.G.,  and Raff, A.D., 1961, Magnetic survey off the west
       coast of North America, 32 to 42 degrees N. latitude:  Geological
       Society of America Bulletin, v. 72, p. 1259-1266.

       Raff,  A.D.,  and Mason, R.G., 1961, Magnetic survey off the west
       coast of North America, 40 to 52 degrees N. latitude:  Geological
       Society of America Bulletin, v. 72, p. 1267-1270.

       Digital  data were provided by  National Geophysical Data Center,
       Boulder, Colo., and Oregon State University, Corvallis, Oregon.


       USSR:
       Makarova,  V.A.,  chief  editor,  1977,  Chart of  the  anomalous
       magnetic field (dT)A of the USSR, 1974:  All Union Aerogeological
       Science Industrial Society,  AEROGEOLCGIYA,  Ministry  of Geology
       of the USSR, Moscow, Scale 1:2,500,000.


       Canada:
       Digital data were provided by Geological Survey of Canada.


       Conterminous United States/Alaska:
       Godson,  R.H.,  1986,  Description  of  magnetic tape  containing
       conterminous  U.S.  magnetic  data in  a  gridded  format:   U.S.
       Department  of  Commerce National Technical  Information  Service
       PB86-197423, 5 p.

       Godson,  R.H.,  1986,  Description  of  magnetic tape  containing
       Alaska  magnetic data in a gridded format:   U.S.  Department  of
       Commerce National Technical Information Service PB86-197399, 5 p.

       Digital data were provided by U.S. Geological Survey.



       MAGSAT Data for North America

       The  MAGSAT project was a NASA effort to measure  the  near-Earth
       magnetic  field,  on  a global basis.   MAGSAT  collected  scaler
       (total-field)  and  three  orthogonal vector  components  of  the
       magnetic  field.


                                      47


       During  its seven and one-half months in orbit (October  1979  to
       June   1980),   this   satellite  provided  the   most   accurate
       measurements  of the global field ever obtained,  as well as  the
       first measurement of the vector field in low-Earth orbit.

       MAGSAT  data have been used to investigate the tectonics  of  the
       continental and oceanic lithosphere, to research the external and
       core fields, and to improve data processing techniques and sensor
       design.   Many  of  the  studies are  documented  in  Geophysical
       Research  Letters (April 1982,  vol.  9,  no.  4) and Journal  of
       Geophysical Research (February 1985, vol. 90, no. B3).

       The data presented on the compact disc represent scalar anomalies
       covering non-auroral latitudes (i.e., 50-degrees N  to 50-degrees
       S) on a two-degree grid interval.

       TOPOGRAPHIC DATA


       Average Elevations and Bathymetry

       Digital  land  and  seafloor  elevations,   gridded  at  5-minute
       intervals,   were  assembled from several uniformly-gridded  data
       bases.   Oceanic  bathymetry  was  compiled  by  the  U.S.  Naval
       Oceanographic  Office  and  revised by them in  1987.   The  land
       elevations  of the conterminous United States were compiled  from
       gridded data supplied by the Defense Mapping  Agency;  elevations
       for   other   land  areas  were  interpolated  by  the   National
       Geophysical  Data  Center  (NGDC) from  10-minute  gridded  modal
       height   data  provided  by  the  U.S.   Navy   Fleet   Numerical
       Oceanographic Center.   While data in this compilation represents
       only  areas in and adjacent to North America,  the entire  global
       set (known as ETOPO5) is also available from NGDC.


       Topography Data for the United States

       These  30-second  grid average elevation values were compiled  by
       the U.S.  Geological Survey,  the National Geodetic  Survey,  the
       Defense Mapping Agency, and the National Geophysical Data Center.

       The  original Digital Terrain Data Base (3-second point data) was
       compiled by the Defense Mapping Agency.   The data were generated
       by digitizing 1-degree by 2-degree (1:250,000) scale  maps.   The
       Defense  Mapping  Agency  selected  every tenth  point  from  the
       Digital Terrain Data Base to create the 30-second point data set.
       These  data  were  rounded to the nearest 20 feet  for  every  30
       seconds of latitude and longitude (approximately 2700 feet on the
       surface of the Earth).

       A copy of the data was then transferred to the National  Geodetic
       Survey (NGS), who reformatted and corrected the data, rounding to
       the nearest 10 meters.   NGS sent a copy of the 30-second data to
       the USGS, who averaged the data by using the four corners of each
       cell.

                                      48



       To  complement  the  30-second land data,  coastal  and  waterway
       bathymetry were developed by the National Geophysical Data Center
       from data archived by the National Ocean Survey (NOS).  Trackline
       data  were averaged into 15-second cells and then  averaged  into
       30-second cells.   In the process of averaging these data, a code
       was  used  to  determine how many 15-second cells  were  used  to
       develop  the 30-second values;  this code is part of the  archive
       record.

       One  of the problems with the 30-second land data is that much of
       the  offshore data were coded with a no-data value of  "1"  which
       represents a valid land elevation.  This created many problems in
       representing coastlines accurately, especially in regions such as
       southern  Florida  and  the Mississippi  Delta.   To  solve  this
       problem  NGDC  decided to merge the NOS bathymetry data with  the
       land data.   First,  a mask was developed to delete the  offshore
       data from the land data set, and then the coastal bathymetry data
       were  added.   The  data are now suitable for  display;  however,
       caution is recommended for those doing detailed coastal studies.

       Included in the coastal data are some inland waterways.   Some of
       these regions are on datums that are other than sea  level.   For
       example:

       Lake Superior  600 feet
       Lake Michigan  577 feet
       Lake Huron  577 feet
       Lake St. Clare  572 feet
       Lake Erie  569 feet
       Lake Ontario  243 feet

       The  above  values represent 1955 datums.   As the datum  changes
       with  time and the surveys used in the averages represent  values
       collected  over  a  long  time,  these  datum  values  should  be
       considered  as  an approximation whose accuracy is  less  than  2
       feet.

       LITHOSPHERIC DATA


       DNAG Seismicity Data

       Construction of the seismicity data base required the analysis of
       more  than  one-half million earthquake epicenters  from  global,
       national,   regional,   and  local  catalogs,  and  other  source
       materials.   Duplicate entries were removed regionally based on a
       comparison  of reported origin times,  epicentral locations,  and
       magnitudes.  The  edited  data base spans an interval  from  1534
       through 1985.






                                      49


       Further details on the rationale used to construct the seismicity
       data  base and detailed regional interpretations can be found  in
       the   seismicity  section  of  Neotectonics  of  North   America,
       Centennial Special Map Volume 1,  by D.B. Slemmons, E.R. Engdahl,
       D.  Blackwell,  and D.  Schwartz (Geological Society of  America,
       Boulder, Colo., in press).

       Members  of  the  working group for the Seismicity Map  of  North
       America (1988) included:

       J. Adams
       P.W. Basham
       N.N. Biswas
       G.A. Bollinger
       D.J. Cash
       E.J. Corbett
       J.P. Eaton
       J.E. Ebel
       P. Einarsson
       W.L. Ellsworth
       E.R. Engdahl*
       S. Gregerson
       F. Buendel
       D.P. Hill
       L.K. Hutton
       K.H. Jacob
       C.E. Johnson
       J.L. King
       J.C. Lahr
       R.S. Ludwin
       B.J. Mitchell
       A.R. Palmer
       P.W. Pomeroy
       W.A. Rinehart
       A.M. Rogers
       G.C. Rogers
       A.S. Ryall
       A.R. Sanford
       R.B. Smith
       C.W. Stover
       G. Suarez
       J.J. Taber
       J.N. Taggart
       P. Talwani
       R.A. Uhrhammer
       R.A. White
       * chairman

       Data sources and the agencies responsible for the compilation and
       integrity  of  each source are shown in  the  following  listing.
       Where  data  from two or more sources overlapped,  the  data  set
       judged   to  have  the highest integrity  was  used.   The  final
       selection  of  data  from  each  source  is  shown  by  the  data
       distribution  index map  which accompanies the Seismicity Map  of
       North America.

                                      50


       DNAG Seismic Data References and Sources:

       North America:
       Abe,  K., 1981, Magnitudes of large shallow earthquakes from 1904
       to 1980:  Physics of the Earth and Planetary Interiors, v. 27, p.
       72-92.

       Abe,  K.,  and Noguchi, S., 1983, Revision of magnitudes of large
       shallow   earthquakes  1897-1912:    Physics  of  the  Earth  and
       Planetary Interiors, v. 33, p. 1-11.

       Bath,   M.,  and  Duda,  S.J.,  1979,   Some  aspects  of  global
       seismicity:  Report No.  1-79,  Seismological Institute, Uppsala,
       Sweden, 41 p.

       Gutenberg,  B., and Richter, C.F., 1954,  Seismicity of the Earth
       and associated phenomena:  Princeton University Press, 310 p.

       Digital  data were also provided by  International  Seismological
       Centre,  Newbury, United Kingdom; Bureau Central International de
       Seismologique,  Strasbourg,  France;  and U.S. Geological Survey,
       Denver, Colo.


       Alaska/Aleutians:
       Boyd,  T.M.,  and Lemer-Lam,  A.,  1988,  Spatial distribution of
       turn-of-the-century  seismicity  along the  Alaska-Aleutian  Arc:
       Bulletin of the Seismological Society of America,  v. 78, p. 636-
       650.

       Engdahl,  E.R.,  1977,   Seismicity  and plate subduction in  the
       central Aleutians, in island arcs, deep sea trenches and back arc
       basins: Maurice Ewing Series, v. 1, p. 259-271.

       Digital  data were provided by U.S.  Geological  Survey,  Denver,
       Colorado  and Menlo Park,  California;  Cooperative Institute for
       Research  in the  Environmental   Sciences,  Boulder,   Colorado;
       Lamont-Doherty  Geological Observatory,  Palisades, New York; and
       University of Alaska, Fairbanks, Alaska.



       Canada:
       Digital data were provided by Geological Survey of Canada.


       Greenland:
       Digital data were provided by Geodetic Institute of Denmark.


       Iceland:
       Digital data were provided by the University of Iceland.




                                      51


       Mid-Atlantic:
       Digital   data   were  provided  by   Lamont-Doherty   Geological
       Observatory.


       Conterminous United States:
       Davis,   S.D.,   Pennington,   W.D.,  and  Carlson,  S.M.,  1985,
       Historical   seismicity   of  the  State  of  Texas--a   summary:
       Transactions,  Gulf Coast Association of Geological Societies, v.
       35, p. 39-44.

       Dewey,  J.W.,  and Gordon,  D.W.,  1984,  Map showing  recomputed
       hypocenters  of earthquakes in eastern and central United  States
       and  adjacent  Canada,   1925-1980:    U.S.  Geological   Survey,
       Miscellaneous Field Studies Map MF-1699 Pamphlet, 39 p.

       Kollman,  A.,  and Zollweg,  J.,  1985, Oregon seismicity--August
       1980 to October 1982:   U.S.  Geological Survey Open File Report,
       84-832, 28 p.

       Smith,  S.W.,  and Knapp, J.S., 1980, The northern termination of
       the San Andreas Fault:  California Division of Mines and Geology,
       Special Report 140, p. 153-164.

       Digital  data were provided by U.S.  Geological Survey,  National
       Geophysical  Data  Center,   Woodward-Clyde  Consultants,  Oregon
       State University,  University of Washington,  California Division
       of  Mines  and  Geology,  University  of  California,  California
       Institute of  Technology,  U.S. Bureau of Reclamation, University
       of Nevada,  Montana Bureau of Mines and Geology,  Idaho  National
       Engineering Laboratory,  University of Utah, New Mexico Institute
       of  Mining  and  Technology,  Los  Alamos  National   Laboratory,
       Electric  Power  Research  Institute,   Saint  Louis  University,
       Oklahoma  Geological   Survey,   Boston  College,   and  Virginia
       Polytechnic Institute and State University.

       Middle America:
       Singh,  S.K., Rodriquez, M., and Espindola, J.M., 1984, A catalog
       of shallow earthquakes of Mexico from 1900 to 1981:   Bulletin of
       the Seismological Society of America, v. 74, p. 267-279.

       White,  R.A.,  and Cifuentes,  I.L., 1988, Seismic history of the
       Middle  America  Trench from Chiapas,  Mexico,  to  El  Salvador:
       Bulletin of the Seismological Society of America (in press).

       Digital  data were provided by National Geophysical Data  Center,
       National University of Mexico, U.S. Geological Survey, Guatemalan
       National  Institute of Seismology,  Volcanology,  Meteorology and
       Hydrology,  Nicaraguan  Institute  of  Territorial  Studies,  and
       National University of Costa Rica.






                                      52


       Crustal Stress Data

       Crustal  stress data for North America were provided by Mary  Lou
       Zoback of the U.S.  Geological Survey,  Menlo  Park,  California.
       The data were compiled as part of the World Stress Map project of
       Working  Group-3  on Intraplate Phenomena for  the  International
       Lithosphere Program.   The goal of this project is to compile and
       interpret a global data base of modern intraplate tectonic stress
       orientations  and stress-magnitude data (where  available).   The
       project  also  studies the relationship of intraplate  seismicity
       and in situ stress patterns.

       Four  main types of tectonic stress indicators were  included  in
       the   data   base:    earthquake   focal   mechanisms,   wellbore
       elongations, in situ stress measurements, and young geologic data
       including   volcanic   alignments   and  fault   slip   analyses.
       Information  recorded  for each data  point  include:   location,
       maximum  horizontal compressive stress azimuth,  type  of  stress
       indicator,   quality,   stress  regime,   depth,  reference,  and
       comments.

       Crustal Stress Data References:

       Zobak,  M.L.,  Nishenko,  S.P., Richardson, R.M., Hasegawa, H.S.,
       and  Zobak,   M.D.,  1986,  Mid-plate  stress,  deformation,  and
       seismicity,  in  The  Geology of North America,  Volume  M.,  the
       Western North Atlantic Region,  Vogt,  P.R.,  and Tucholke, B.E.,
       editors, Geological Society of America, p. 297-312.

       Zoback,  M.L.,  and Zoback,  M.D.,  1980,  State of stress in the
       conterminous United States:   Journal of Geophysical Research, v.
       85, p. 6113-6156.

       Zoback,  M.L.,  and Zoback,  M.D., 1988, Tectonic stress field of
       the  continental United States:   Geological Society  of  America
       Memoir (in press).


       DNAG Thermal Aspects Data

       A comprehensive data base of heat flow and ancillary measurements
       for  North  America was compiled as basis for preparation of  the
       DNAG  Thermal  Aspects  Map of North  America  (in  press).   The
       objective  of  the  compilation  was  to  provide  relevant  site
       information  so that investigators and researchers would be  able
       to  study relationships between the heat flow data  and  geology,
       elevation,   physiographic  province,  location,  and  geothermal
       gradient.  Information about each site is divided into five basic
       groups:   hole  location  and  date of  temperature  measurement,
       minimum and maximium values,  gradient and heat flow results  per
       depth interval, lithologic information, and general comments.





                                      53


       DNAG Thermal Aspects Data Sources:

       United States and Central America Geothermal Data Base:
       Digital data were compiled by David D. Blackwell, John L. Steele,
       and Larry S.  Carter, Department of Geological Sciences, Southern
       Methodist University, Dallas, Texas.

       Assisting  in the compilation of United States data were  Douglas
       Smith,  University of Florida;  Edward R.  Decker,  University of
       Maine at Orono; Paul Morgan, Northern Arizona University; William
       R.  Gosnold,  University  of North Dakota;  Marshall Reiter,  New
       Mexico  Institute of Technology;  and James Witcher,  New  Mexico
       State University.


       Canada Geothermal Data Base:
       Digital  data  were compiled by  Alan  M.  Jessop,  Institute  of
       Sedimentary  and Petroleum Geology,  Geological Survey of Canada,
       Calgary, Alberta, Canada.


       Canadian Cordillera Geothermal Data Base:
       Digital  data were compiled by Trevor Lewis,  Pacific  Geoscience
       Center,  Geological Survey of Canada,  Sidney,  British Columbia,
       Canada.


       DNAG Thermal Aspects Data References:

       Steele,  John L.,  and Blackwell,  David D.,  1988,  Appendix  A,
       Description  of  the  GSA-DNAG Geothermal Map  of  North  America
       Master  File Data Base System,  in U.S.  Geothermal Database  and
       Oregon  Cascade  Thermal Studies:   U.S.  Department  of  Energy,
       DOE/ID/12623-1, Southern Methodist University, Dallas, Texas.

       Slemmons, D.B., Engdahl, E.R., Zoback, M.D., Blackwell, D.D., and
       Schwartz,  D.,  editors,  1989,  Neotectonics  of North  America:
       Geological Society of America Centennial Special Map Volume 1 (in
       press).

       A  complete  list of references for the DNAG map and data may  be
       found  in  Appendix  B  of  U.S.   Department  of  Energy  Report
       DOE/ID/12623-1,  U.S.  Geothermal  Database  and  Oregon  Cascade
       Thermal Studies, by David D. Blackwell, John L. Steele, and Larry
       Carter (Southern Methodist University, 1988).  The references are
       too numerous to list here.










                                      54


       NOAA AVHRR DATA


       Satellite Radiometric Data

       Advanced  Very  High  Resolution  Radiometer  (AVHRR)  data  were
       obtained  from the National Environmental  Satellite,  Data,  and
       Information Service's Satellite Data Services Division.  The data
       were  in  the "Plate Carree" latitude/longitude format  and  were
       converted by the National Geophysical Data Center into  10-minute
       grids.   Channels  1,  2 and 5 were chosen for time periods which
       were  judged to be relatively cloud-free.   These  periods  cover
       June and November, 1986, for Julian days 162 - 168 and 316 - 322,
       respectively.   George  Stevens  of the  NOAA/NESDIS  Interactive
       Processing Branch selected these dates as being relatively useful
       for  regional  geological  analysis,  as well as  for  vegetation
       studies.


       Channel Wavelength               Primary Purpose
       (micrometers)
       10.58 - 0.68 Visible spectrum - cloud mapping

       20.725 - 1.10Reflected infrared - surface water boundaries

       511.50 - 12.50Thermal infrared - water vapor correction

       Normalized Vegetation Index (NVI) Data

       A normalized vegetation index was computed as  NVI = (Channel 2 -
       Channel  1)  /  (Channel 2 +  Channel  1).   Since  the  spectral
       reflectance  of  chlorophyll  pigment is more  than  three  times
       greater  in  the  reflected infrared spectrum  than  the  visible
       spectrum, this index provides a good indicator for monitoring the
       vigor  and  density  of  green  vegetation.    The  normalization
       procedure is generally preferred because it partially compensates
       for  changing illumination conditions,  surface slope and viewing
       aspect.  It  should be noted that water,  snow,  and clouds  have
       larger AVHRR responses in the visible spectrum than the reflected
       infrared,  and therefore these features have negative NVI.   Rock
       and  soil tend to result in NVI values of  zero,  and  vegetation
       density  tends  to range from 0.1 to 0.6 (the higher  values  are
       associated   with  greater  density).    Atmospheric  effects  of
       scattering  and  clouds act to increase visible  reflectance  and
       thus reduce the values of NVI.

       Detailed  information  on  operational  AVHRR  data  and  derived
       products can be obtained by contacting:

       NOAA/NCDC/Code ECC6
       Satellite Data Services Division
       Princeton Office Building, Suite 100
       Washington, DC 20233
       Telephone: [phone]


                                      55


       Release 1.1Your Data Center
        for Solid Earth Geophysics


       Your Data Center for Solid Earth Geophysics


       PROGRAM OVERVIEW


       The  National  Oceanic  and  Atmospheric  Administration   (NOAA)
       collects,  manages,  and disseminates scientific data that result
       from  an inquiry into the environment.   The National Geophysical
       Data Center (NGDC), one of the several data management centers of
       NOAA,  is  responsible  for  data activities  in  the  fields  of
       seismology,   gravity,   topography,  geomagnetism,  geothermics,
       marine  geology  and geophysics,  and solar-terrestrial  physics.
       NGDC also provides facilities for World Data Center-A  (including
       the  disciplines  of Solid Earth Geophysics,  Marine Geology  and
       Geophysics,  Solar-Terrestrial Physics,  and Glaciology--Snow and
       Ice) under the auspices of the National Academy of Sciences.

       This overview focuses on the principal products and services NGDC
       provides  through  its Solid Earth  Geophysics  Division  (SEGD).
       Among  the  most important activities of SEGD are  acquiring  and
       archiving  data,  processing  and formatting data  into  standard
       sets,   developing  useful  data  products  for  customers,   and
       disseminating  data to the scientific,  academic,  and industrial
       communities.

       SEGD data support many scientific and engineering endeavors, both
       in  the  assessment  and  mitigation  of  geologic  hazards  (for
       example,  earthquakes  and tsunamis) and in the  exploration  for
       minerals and petroleum.   Our data also support basic and applied
       research   in   many  of  the  Earth  science   and   engineering
       disciplines.    Customers   include  the  general  public,   data
       managers,   engineers,   and  scientists  in  private   industry,
       academia, and federal and state governments.

       SEGD  provides  data  and  products in  the  fields  of  gravity,
       topography,    seismology   (including   earthquake   seismology,
       engineering  seismology,  and tsunami),  land seismic reflection,
       geomagnetism  (Earth-surface,   airborne,  and  satellite  data),
       geothermics, and geochemistry.  Typical services include:

       Selective searches of data bases
       Customized data retrieval and output
       Computer-generated   data   products--including    formatted
       listings, data summaries, map plots
       Technical reports, catalogs of data inventories
       Publication  of  selected  reports for  other  organizations
       (through World Data Center-A)
       International data exchange (through World Data Center-A)
       Data systems for managing all types of geoscience data
       Data management and archival for special projects

                                      56


       WORLD DATA CENTER A

       World Data Center-A for Solid Earth Geophysics (WDC-A)  exchanges
       data internationally,  and assists scientists in obtaining copies
       of  original or calibrated data held by other scientists or other
       world data centers.  WDC-A also publishes data reports, maps, and
       compilations  (including selected manuscripts) for  international
       organizations.    Both  our  national  and  world  data   centers
       encourage data-exchange agreements with other organizations.



       VISITING SCIENTISTS PROGRAM

       NGDC and WDC-A operate a modest visiting scientist program, which
       provides space and access to computers,  plotters, and data files
       to  researchers  who  need  to access  data.   Contact  NGDC  for
       details.



       COOPERATIVE INSTITUTES

       To  foster  the  development of  technology  in  remote  sensing,
       mineral  and energy resources,  and management and application of
       geoscience  data bases,  NGDC has joined with the  University  of
       Colorado and the Colorado School of Mines to form two cooperative
       institutes:

       Cooperative Institute for Research in Environmental Sciences
       (CIRES)
       Cooperative  Institute  for Geoscience Data  Management  and
       Applications (CIGMA)

       CIRES,  managed by the University of Colorado (Boulder), conducts
       a  wide range of research:   glaciology (including directing  the
       National  Snow  and  Ice Data Center for  NGDC),  remote  sensing
       (including  operating  the newly formed Center for the  Study  of
       Earth from Space), seismology, and many other disciplines.

       CIGMA, operated by the Colorado School of Mines (Golden), fosters
       research   and   development  focused  on  the   management   and
       application of large geoscience data bases.

       Additionally,    NGDC's   parent   organization,   the   National
       Environmental  Satellite,   Data,  and  Information  Service,  is
       establishing  several cooperative institutes that will  focus  on
       remote sensing applications to natural resources.   Each of these
       institutes  increases  the  synergetic  benefits  of  cooperative
       research and development for scientists in government,  academia,
       and industry.





                                      57


       STAFF CREDITS

       Many  workers  in the National Geophysical Data Center and  joint
       institutes were involved in the preparation of the original  NOAA
       Geophysics of North America CD-ROM and the related software:

       Project Authorization:Michael A. Chinnery, Director
       National Geophysical Data Center

       Project Concept and Guidelines:Herbert Meyers, Chief
       Solid Earth Geophysics Division

       Project Management:   Allen M. Hittelman

       Data Preparation:
       W.  Minor Davis,  Ray E.  Habermann,  John O. Kinsfather, John J.
       Kineman,  Ronald W.  Buhmann, Peter W. Sloss, Susan E.L. Godeaux,
       and David T.  Dater.  Support was also provided by Richard Hansen
       and  Cemal  Erdemir of the Cooperative Institute  for  Geoscience
       Data  Management  and Applications (CIGMA) at Colorado School  of
       Mines.

       Access Software:
       John O.  Kinsfather,  Allen M. Hittelman, Ray E. Haberman, Gerald
       H. Orita, Carl C. Abston, W. Minor Davis, and Chris Wells.

       Documentation:
       Allen M.  Hittelman,  Ronald W. Buhmann, Joy A. Ikelman, and Jean
       Pfleiderer.

       Advisory:
       Richard Hansen and David A. Hastings.


       Release 1.1Appendix A:  Directory Tree


       Appendix A:  Directory Tree

       The  following lists the file names and byte sizes of  the  image
       files contained on the Geophysics of North America data base.



       BOUNDARY

       COASTHI
       COASTHI.0076,568
             COASTHI.0148,072
       COASTHI.0292,264
       COASTHI.0362,288
       COASTHI.04133,184
       COASTHI.05110,960
       COASTHI.0637,640
       COASTHI.07366,224

                                      58


       COASTHI.0834,784
       COASTHI.09178,584
       COASTHI.1048,000
       COASTHI.1115,896
       COASTHI.12815,432
       COASTHI.13121,560
       COASTHI.1463,640
       COASTHI.1551,800
       COASTHI.1625,080
       COASTHI.17175,328
       COASTHI.1833,408
       COASTHI.1967,832
       COASTHI.2090,280
       COASTHI.2144,408
       COASTHI.22173,248
       COASTHI.23661,024
       COASTHI.2486,224
       COASTHI.2535,704
       COASTHI.2631,760
       COASTHI.2747,504
       COASTHI.2854,336
       COASTHI.2956,312
       COASTHI.3042,424
       COASTHI.3131,216
       COASTHI.3269,128
         COASTHI.3357,944
         COASTHI.3450,216
         COASTHI.3531,448
         COASTHI.3644,592
         COASTHI.37240,728
         COASTHI.38115,440
         COASTHI.3950,568
         COASTHI.4031,432
         COASTHI.DOC6,012
         COASTHI.INX15,680

        COASTLO
         COASTLO.0035,880
         COASTLO.0138,640
         COASTLO.0210,472
         COASTLO.0315,704
         COASTLO.0421,072
         COASTLO.0538,176
         COASTLO.DOC3,141
         COASTLO.INX7,080

        COUNTY
         COUNTY.0014,752
         COUNTY.0111,392
         COUNTY.0212,384
         COUNTY.034,000
         COUNTY.042,704
         COUNTY.054,384
         COUNTY.062,016
         COUNTY.079,496

                                      59


         COUNTY.085,584
         COUNTY.092,112
         COUNTY.1011,272
         COUNTY.119,112
         COUNTY.1222,752
         COUNTY.1341,784
       COUNTY.142,552
       COUNTY.153,088
       COUNTY.168,040
       COUNTY.177,440
       COUNTY.187,048
       COUNTY.195,584
       COUNTY.202,416
       COUNTY.214,544
       COUNTY.225,344
       COUNTY.238,568
       COUNTY.247,784
       COUNTY.257,232
       COUNTY.266,584
       COUNTY.272,808
       COUNTY.282,144
       COUNTY.297,272
       COUNTY.308,584
       COUNTY.315,400
       COUNTY.322,336
       COUNTY.333,704
       COUNTY.348,784
       COUNTY.35808
       COUNTY.3635,664
       COUNTY.DOC5,615
       COUNTY.INX77,200

       STATE
       STATE.0067,392
       STATE.0172,960
       STATE.0242,184
       STATE.0337,080
       STATE.0432,328
       STATE.0578,896
       STATE.0641,312
       STATE.DOC3,098
       STATE.INX13,380


       CONTOUR

       DNAGGRAV
       DGRAV.0011,248
             DGRAV.017,288
             DGRAV.0217,456
       DGRAV.0315,808
       DGRAV.0417,088
       DGRAV.0541,424
       DGRAV.0675,744
         DGRAV.0786,320

                                      60


         DGRAV.0884,848
         DGRAV.09111,792
         DGRAV.1016,056
         DGRAV.119,240
         DGRAV.1223,824
         DGRAV.1322,728
         DGRAV.1474,184
         DGRAV.1596,904
         DGRAV.16109,936
         DGRAV.1789,392
         DGRAV.18103,840
         DGRAV.19116,664
         DGRAV.2010,272
         DGRAV.219,040
         DGRAV.2226,728
         DGRAV.23142,688
         DGRAV.2448,848
         DGRAV.2556,000
         DGRAV.2660,848
         DGRAV.2785,768
         DGRAV.2838,376
         DGRAV.2926,144
         DGRAV.3020,624
         DGRAV.3116,240
         DGRAV.3234,200
         DGRAV.33119,040
         DGRAV.3467,792
         DGRAV.3545,672
         DGRAV.3648,048
         DGRAV.3748,680
         DGRAV.3829,368
         DGRAV.3921,688
         DGRAV.4016,024
         DGRAV.4126,184
         DGRAV.4263,360
         DGRAV.4378,192
         DGRAV.4458,360
         DGRAV.4571,552
         DGRAV.4641,936
         DGRAV.4752,776
         DGRAV.4833,248
         DGRAV.4927,744
         DGRAV.5018,992
         DGRAV.5115,928
         DGRAV.5250,552
         DGRAV.5371,544
         DGRAV.5436,024
       DGRAV.5546,760
       DGRAV.5643,096
       DGRAV.5751,440
       DGRAV.5856,704
       DGRAV.5934,552
       DGRAV.6023,160
       DGRAV.6124,416
       DGRAV.6256,552

                                      61


       DGRAV.63121,504
       DGRAV.6434,696
       DGRAV.6534,624
       DGRAV.6655,200
       DGRAV.6755,912
       DGRAV.6858,392
       DGRAV.6947,136
       DGRAV.7029,552
       DGRAV.7180,232
       DGRAV.7291,208
       DGRAV.7398,688
       DGRAV.7442,920
       DGRAV.7544,504
       GRAV.7671,832
       DGRAV.7785,544
       DGRAV.7840,264
       DGRAV.7932,184
       DGRAV.8094,936
       DGRAV.8177,216
       DGRAV.8248,272
       DGRAV.8343,032
       DGRAV.8467,144
       DGRAV.85143,504
       DGRAV.86103,584
       DGRAV.8780,040
       DGRAV.8829,456
       DGRAV.8936,480
       DGRAV.9090,904
       DGRAV.9155,288
       DGRAV.9261,328
       DGRAV.93110,152
       DGRAV.94156,520
       DGRAV.95183,432
       DGRAV.96126,504
       DGRAV.97134,584
       DGRAV.9855,496
       DGRAV.9942,904
       DGRAV.DOC11,043
       DGRAV.INX315,500

        DNAGMAG
         DMAG.00017,856
         DMAG.00161,976
         DMAG.002208,160
         DMAG.00376,968
         DMAG.00473,496
         DMAG.005150,176
         DMAG.006155,104
         DMAG.007150,536
         DMAG.00867,344
         DMAG.00915,800
         DMAG.01035,144
         DMAG.011233,936
         DMAG.012164,520
         DMAG.013184,464

                                      62


         DMAG.01473,616
         DMAG.01526,688
         DMAG.01624,096
         DMAG.01753,784
         DMAG.018181,864
         DMAG.019165,512
         DMAG.02076,992
         DMAG.0212,624
         DMAG.02212,056
         DMAG.02334,272
         DMAG.02476,664
         DMAG.025137,584
         DMAG.026203,504
         DMAG.027227,496
         DMAG.028119,720
         DMAG.02944,720
         DMAG.0304,808
         DMAG.03113,192
         DMAG.03262,648
         DMAG.033102,824
         DMAG.034328,760
         DMAG.035486,576
         DMAG.036284,664
         DMAG.03758,496
         DMAG.03867,896
         DMAG.0395,464
         DMAG.04015,856
         DMAG.04170,504
         DMAG.042221,160
         DMAG.043408,768
         DMAG.044346,504
         DMAG.045220,784
         DMAG.04688,584
       DMAG.04760,184
       DMAG.04812,216
       DMAG.049102,384
       DMAG.050212,544
       DMAG.051234,664
       DMAG.052318,304
       DMAG.053244,272
       DMAG.054392,800
       DMAG.055261,480
       DMAG.05629,520
       DMAG.05730,416
       DMAG.058223,600
       DMAG.059110,864
       DMAG.060195,984
       DMAG.061342,072
       DMAG.062193,376
       DMAG.063614,872
       DMAG.064413,008
       DMAG.06540,536
       DMAG.06617,176
       DMAG.067133,448
       DMAG.06818,496

                                      63


       DMAG.069148,880
       DMAG.070446,136
       DMAG.071545,872
       DMAG.072679,056
       DMAG.073354,336
       DMAG.07464,784
       DMAG.07546,056
       DMAG.07662,752
       DMAG.07779,192
       DMAG.078197,192
       DMAG.079423,224
       DMAG.080543,024
       DMAG.081471,472
       DMAG.082239,864
       DMAG.083147,560
       DMAG.08414,616
       DMAG.085129,392
       DMAG.086149,496
       DMAG.087197,304
       DMAG.088409,360
       DMAG.089615,544
       DMAG.090663,376
       DMAG.091152,176
       DMAG.092109,064
       DMAG.0939,616
       DMAG.09487,512
         DMAG.095159,264
         DMAG.096179,432
         DMAG.097194,736
         DMAG.098725,280
         DMAG.099650,008
         DMAG.100160,712
         DMAG.101101,456
         DMAG.1028,752
         DMAG.10378,904
         DMAG.104105,872
         DMAG.105182,664
         DMAG.106157,960
         DMAG.107696,552
         DMAG.108333,000
         DMAG.109149,728
         DMAG.11066,256
         DMAG.1111,192
         DMAG.11224,744
         DMAG.113192,296
         DMAG.114188,152
         DMAG.115146,448
         DMAG.11677,056
         DMAG.11747,440
         DMAG.118139,600
         DMAG.119161,632
         DMAG.12079,488
         DMAG.12180
         DMAG.12282,504
         DMAG.123286,632

                                      64


         DMAG.124221,256
         DMAG.125115,008
         DMAG.126455,416
         DMAG.127356,848
         DMAG.12857,056
         DMAG.12963,360
         DMAG.130217,352
         DMAG.131520,584
         DMAG.132125,192
         DMAG.DOC13,591
         DMAG.INX4,166,780

        ETOPO5
         ETOPO5.0072,400
         ETOPO5.0175,704
         ETOPO5.02231,624
         ETOPO5.03238,224
         ETOPO5.04266,496
         ETOPO5.05195,176
       ETOPO5.06100,296
       ETOPO5.0739,400
       ETOPO5.08153,560
       ETOPO5.09128,136
       ETOPO5.10319,600
       ETOPO5.11243,416
       ETOPO5.1286,288
       ETOPO5.13158,000
       ETOPO5.14156,576
       ETOPO5.15123,464
       ETOPO5.16200,464
       ETOPO5.17161,856
       ETOPO5.1855,496
       ETOPO5.19167,136
       ETOPO5.20226,048
       ETOPO5.21160,040
       ETOPO5.22126,528
       ETOPO5.2363,576
       ETOPO5.24101,136
       ETOPO5.25111,016
       ETOPO5.26366,192
       ETOPO5.27310,024
       ETOPO5.28176,296
       ETOPO5.2969,424
       ETOPO5.3088,304
       ETOPO5.3145,072
       ETOPO5.3290,032
       ETOPO5.33245,680
       ETOPO5.34347,944
       ETOPO5.35118,824
       ETOPO5.36120,568
       ETOPO5.3755,384
       ETOPO5.3827,064
       ETOPO5.3938,432
       ETOPO5.40245,176
       ETOPO5.41196,344

                                      65


       ETOPO5.42182,152
       ETOPO5.4397,032
       ETOPO5.4446,048
       ETOPO5.4598,456
       ETOPO5.46362,784
       ETOPO5.47311,312
       ETOPO5.48127,712
       ETOPO5.49129,376
       ETOPO5.50111,488
       ETOPO5.51156,128
       ETOPO5.52236,816
       ETOPO5.53170,072
         ETOPO5.5489,304
         ETOPO5.55158,736
         ETOPO5.56111,968
         ETOPO5.57208,968
         ETOPO5.58338,056
         ETOPO5.59178,344
         ETOPO5.6090,336
         ETOPO5.61138,304
         ETOPO5.62173,664
         ETOPO5.63254,496
         ETOPO5.64246,032
         ETOPO5.65235,528
         ETOPO5.66111,152
         ETOPO5.67165,912
         ETOPO5.68164,864
         ETOPO5.69259,104
         ETOPO5.70133,456
         ETOPO5.71155,232
         ETOPO5.INX1,096,340
         ETOPO5B.DOC8,701


        ISOSTAT
         IGRAV.00115,016
         IGRAV.0147,496
         IGRAV.02140,848
         IGRAV.03234,304
         IGRAV.049,408
         IGRAV.05149,352
         IGRAV.06171,704
         IGRAV.079,688
         IGRAV.08107,888
         IGRAV.09136,864
         IGRAV.1031,912
         IGRAV.11158,712
         IGRAV.12106,856
         IGRAV.1385,600
         IGRAV.14133,400
         IGRAV.15109,424
         IGRAV.1696,680
         IGRAV.1740,736
         IGRAV.18129,880
         IGRAV.19127,512

                                      66


         IGRAV.2062,896
         IGRAV.21120,080
         IGRAV.22134,000
         IGRAV.2361,808
         IGRAV.2437,616
       IGRAV.DOC4,827
       IGRAV.INX175,240

       MAGSAT
       MAGSAT.0097,504
       MAGSAT.01157,896
       MAGSAT.02118,264
       MAGSAT.DOC2,976
       MAGSAT.INX7,360


       POINT

       SEISMIC
       EQ.0072,552
       EQ.0172,384
       EQ.0271,904
       EQ.0372,096
       EQ.0472,096
       EQ.0571,568
       EQ.0671,640
       EQ.0771,520
       EQ.0870,608
       EQ.0970,776
       EQ.1071,640
       EQ.1170,680
       EQ.1269,672
       EQ.1370,008
       EQ.1466,456
       EQ.1566,048
       EQ.1664,992
       EQ.1763,456
       EQ.1861,992
       EQ.1956,808
       EQ.2054,120
       EQ.2153,928
       EQ.2253,520
       EQ.2350,928
       EQ.2444,064
       EQ.2542,864
       EQ.2630,432
       EQ.2730,312
       EQ.2818,600
       EQ.2914,904
       EQ.308,136
       EQ.312,736
       EQ.321,536
       EQ.DOC3,259
        STRESSB23,142
        STRESSB.DOC1,910

                                      67


        THERMALB147,600
        THERMALB.DOC1,422


       RASTER

        AVHRR
         AVHRR.DOC3,587
         JUN86.CH1974,160
         JUN86.CH2974,160
         JUN86.CH5974,160
         JUN86.NVI974,160
         NOV86.CH1974,160
         NOV86.CH2974,160
         NOV86.CH5974,160
         NOV86.NVI974,160

        GRAV
         DGRAV15,693,696
         ISOSTATB1,958,138

        MAG
         DMAG16,640,640
         MAGSATB10,379,042

        RASTER.DOC3,373


        SUMMARY
         DGRAV.ALL327,104
         DGRAV.IMG112,000
         DMAG.ALL346,680
         DMAG.IMG112,000
         ETOPO5.ALL293,222
         ETOPO5.IMG112,000
         GNA_AREA.IMG112,000
         ISOSTAT.ALL272,214
         ISOSTAT.IMG112,000
         JUN86.ALL244,080
         JUN86.IMG112,000
         MAGSAT.ALL217,482
         MAGSAT.IMG112,000
         NOV86.ALL244,080
         NOV86.IMG112,000
         TOPO30.ALL345,696
         TOPO30.IMG112,000


       TOPO
       ETOPO5B4,672,082
       TOPO3044,928,000
       TOPO30.2348,486,400
       TOPO30.2407,737,600
       TOPO30.2457,737,600
       TOPO30.2507,737,600

                                      68


       TOPO30.2557,737,600
       TOPO30.2607,737,600
       TOPO30.2657,737,600
       TOPO30.2707,737,600
       TOPO30.2757,737,600
       TOPO30.2807,737,600
       TOPO30.2856,739,200
       TOPO30.DOC2,995

       Totals:  525 files; 248,651,160 bytes

       Release 1.1Appendix B:  Running Utilities


       Appendix B:  Running Utilities



       CAVEAT


       The  utilities offered in this release have not received as  much
       quality control as the main access software.   Furthermore,  they
       may  contain  fewer  "user  entry"  checking  routines.    Please
       exercise caution when using these features.

       Future utilities may be contributions from users of this product,
       and  these routines also may not be fully tested by the  National
       Geophysical Data Center.




       SHOW UTILITY


       Introduction

       The "SHOW" utility can be used to display saved images in a slide
       show type presentation on your computer.   A series of up to nine
       EGA  graphic  images  may be presented sequentially,  or  in  any
       order, within each SHOW.


       Saving Images

       The image files are saved by options within the access  software.
       To save an image during your VIEW session,  enter SCREEN function
       and  then select the SAVE option.   To save a profile during your
       VIEW session,  use the CTRL-S function while viewing the profile.
       Both  of  these  files are saved with a  name  you  provide  (for
       example, IMAGE1) and a ".BMP" file name extension.




                                      69


       Creating Your Show

       At  a DOS prompt,  enter the image (or profile) names you created
       without the ".BMP" extension as follows:

       Show Image1 Image2 Image3 Image4 Image5 .... Image9


       Displaying Your Show

       When the SHOW utility is executed, the first image will appear on
       the screen in several seconds.   Your keyboard number keys may be
       used to display your other saved images within the SHOW.  The "2"
       (numeric)  key  will display Image2,  the "4"  key  will  display
       Image4,  and so on.   You can use the "PgDn" key to view the next
       image  or the "PgUp" key to view the previous image.   Also,  the
       "Home"  and  "End"  keys will let you view  the  first  and  last
       images,  respectively.   To exit the SHOW utility,  press the ESC
       key.



       MAKE LABEL UTILITY


       Introduction

       The "MAKE LABEL" utility helps the user display their own gridded
       data within the access software. Having displayed one's own data,
       the  user may then overlay boundary data and other data contained
       on the CD-ROM (e.g., earthquakes, topography contours, etc.).

       In  the  Geophysics of North America data base  access  software,
       each  data set that can be displayed is summarized with  a  label
       file.   This  information is used to define (among other  things)
       certain  default  conditions,  such as:  (1) the limits  of  VIEW
       range,  should the user wish to view ALL of the data, and (2) the
       limits  of the data range,  should the user wish to use a default
       color palette.   The label file has a name identical to the  data
       file,  except for the file name extension.  The software will add
       an  ".LBL"  extension to this name to distinguish the label  file
       from the data file.


       Grid Requirements

       The input matrix must be a two dimensional array with each  value
       represented  as a 16-bit binary field.   The grid spacing must be
       in  a latitude-longitude projection with grid intervals in  units
       of minutes (e.g.,  2.5-minutes).   The sequence within the  array
       should be from left to right then top to bottom.   Therefore, the
       first value will be in the northwestern corner and the last value
       will be in the southeastern corner.



                                      70


       Building a Label File

       The  MAKE  LABEL  utility prompts the user to  provide  input  to
       critical  fields  within  the label  format.   Any  fields  whose
       parameters known (based upon the grid requirements defined above)
       will be automatically set.   Additionally the software makes some
       assumptions   with   respect  to  other  label   fields.    These
       assumptions include:  (1) the grid has no header, (2) the missing
       value data flags are "-9999",  and (3)the registration within the
       cell is "center of cell".  If any of these assumptions are wrong,
       or if the user wishes to add comments to the label file,  a  text
       editor can be used.   The user is prompted to provide information
       as follows:

       File  Name:   Your  default directory will appear.   If  this  is
       correct, simply add a "\" and your file name.  The name should be
       identical  to  your data file name.   The software  utility  will
       append a ".LBL" extension to the label file.

       Descriptive  Title:   Enter a short title that will describe  the
       type of data you are using.

       Number  of  Rows & Columns:   Enter the dimensions of your  grid.
       Rows are horizontal and columns are vertical.

       Data Units:  Enter the appropriate units of measure.

       Maximum  and Minimum Data Values:   Preferably enter the  largest
       and smallest values within your grid.   If this is unknown, enter
       the  reasonable  range of values for your type  of  data.   These
       values  are  used to assign colors associated  with  the  default
       palette.

       Latitude  & Longitude Limits:   Enter the geographical limits  of
       your array.

       Grid Size:  Enter the appropriate grid spacing.

       After  completing  MAKE LABEL,  you will be returned to your  DOS
       prompt.   To  use your new file,  enter the VIEW/IMAGE  menu  and
       input your file name into the "User File".   You can then proceed
       to plot your data and overlay data that are on the CD-ROM.














                                      71