Download Data
Arc/Info Export Files
There are two ARC/INFO export files (.e00) available
for the San Diego Margin on this CD-ROM;
1. Bathymetry - Depth
sd_bathy.e00.gz
2. Backscatter - Digital number (DN) associated with the reflected energy
off the seafloor
sd_back.e00.gz
Full Resolution TIFF Images
There are three full resolution TIFF images available
for the San Diego Margin on this CD-ROM.
These files can be added to a GIS system by creating
a world file using the information from the Arc/Info Grid Information below.
Or these files can be directly opened in many image
processing programs such as Adobe Photoshop and Adobe Illustrator.
1. sd_shd.tif.gz
: Shaded relief of bathymetry using a multi-directional
hillshading AML **
2. sd_bathy.tif.gz : Bathymetry
3. sd_back.tif.gz
: Backscatter
** Multi-directional
hillshading AML created by Florence Wong, U.S. Geological Survey, Menlo
Park CA.
Formal Metadata
Download Instructions
1. Download compressed ARC/INFO export and TIFF
files into drive and/or folder.
2. Uncompress files using decompression program.
There are different decompressing programs for specific computer platforms.
- UNIX usually has a version of GZIP already
unstalled on the system. If not, there are four of the more common GZIP
programs on this CD-ROM (Alpha Dec, SGI, Sparc-Solaris 2.5 and 2.6). These
can be found in the top directory of this CD-ROM in the GZIP folder under
UNIX. If you are on a different system go to www.gzip.org to find
the GZIP program that will work for you.
- Window users may use Winzip to decompress
these files. There is also a freeware Windows version of GZIP on this CD-ROM.
This can be found in the top directory of this CD-ROM in the GZIP folder
under Windows.
-Macintosh users may use MacGZIP. There is a copy on this CD-ROM. This
can be found in the top directory of this CD-ROM in the GZIP folder under
Mac. |
3 "Import" the Arc/Info export files
using the grid option.
Data Collection
The San Diego Margin from Mission Bay to the Mexican
Border was mapped between March 26 and April 4, 1998 using a Kongsberg Simrad
EM-300 Multibeam System hull mounted to C&C Technologies' RV Ocean Alert.
For more information, refer to USGS, Open File Report 98-475.
Processing Steps
1. Bathymetry and backscatter data processed on
Silicon Graphic computer using software developed by the Ocean Mapping Group,
University of New Brunswick. (see USGS Open
File Report 98-509, The Bathymetry of Lake Tahoe, California-Nevada)
2. Processed data downloaded to a Sun Sparc Ultra 2, running Solaris 2.5
as an ascii file (longitude, latitude, depth, or backscatter DN value)
3. In Arc/Info 7.1.2 a point coverage is created from the ascii file.
4. Point coverge is projected from Geographic Coordinate System to UTM projection.
5. Projected point coverage is gridded using IDW (Inverse Distance Weighted)
function.
6a. Grid is exported to Arc/Info export (.e00) file.
6b. Grid is converted to a TIFF image using the "Gridimage" command.
7. Both the export and TIFF files are compressed using UNIX version of GZIP.
Arc/Info Grid Information
Bathymetry
| Cell Size = |
16.000 |
| Data Type: |
Floating Point |
| Number of Rows= |
2588 |
| Number of Columns = |
1922 |
| |
|
| BOUNDARY |
|
| Xmin = |
446139.844 |
| Xmax = |
476891.844 |
| Ymin = |
3601439.750 |
| Ymax = |
3642847.750 |
| |
|
| STATISTICS |
|
| Minimum Value = |
-1225.735 |
| Maximum Value = |
-17.874 |
| Mean = |
-396.057 |
| Standard Deviation = |
334.083 |
| |
|
| COORDINATE SYSTEM DESCRIPTION |
|
| Projection |
UTM |
| Zone |
11 |
| Datum |
WGS84 |
| Units |
METERS |
| Spheroid |
WGS84 |
Backscatter
| Cell Size = |
16.000 |
| Data Type: |
Floating Point |
| Number of Rows= |
2590 |
| Number of Columns = |
1922 |
| |
|
| BOUNDARY |
|
| Xmin = |
446134.906 |
| Xmax = |
476886.906 |
| Ymin = |
3601404.750 |
| Ymax = |
3642844.750 |
| |
|
| STATISTICS |
|
| Minimum Value = |
99.524 |
| Maximum Value = |
248.447 |
| Mean = |
185.910 |
| Standard Deviation = |
9.738 |
| |
|
| COORDINATE SYSTEM DESCRIPTION |
|
| Projection |
UTM |
| Zone |
11 |
| Datum |
WGS84 |
| Units |
METERS |
| Spheroid |
WGS84 |
|