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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: (303) 497-6521; Fax: (303) 497-6513.
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., (303) 447-2020.
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: (301) 763-8400
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