Download Data

Arc/Info Export Files

There are two ARC/INFO export files (.e00) availablefor central San Francisco Bay on this CD-ROM;

1. Bathymetry - Depth


2. Backscatter - Digital number (DN) associated with the reflected energyoff the seafloor


Full Resolution TIFF Images

There are three full resolution TIFF images availablefor the central San Francisco Bay on this CD-ROM.

These files can be added to a GIS system by creatinga world file using the information from the Arc/Info Grid Information below.

Or these files can be directly opened in many imageprocessing programs such as Adobe Photoshop and Adobe Illustrator.

1. sf_shd.tif.gz: Shaded relief of bathymetry using a multi-directionalhillshading AML **

2. sf_bathy.tif.gz : Bathymetry

3. sf_back.tif.gz: Backscatter

** Multi-directionalhillshading AML created by Florence Wong, U.S. Geological Survey, MenloPark CA.

C2-97-SF Formal Metadata

C3-97-SF Formal Metadata

Download Instructions

1. Download compressed ARC/INFO export and TIFFfiles 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 alreadyunstalled on the system. If not, there are four of the more common GZIPprograms on this CD-ROM (Alpha Dec, SGI, Sparc-Solaris 2.5 and 2.6). Thesecan be found in the top directory of this CD-ROM in the GZIP folder underUNIX. If you are on a different system go to to findthe GZIP program that will work for you.

- Window users may use Winzip to decompressthese 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 folderunder Windows.

-Macintosh users may use MacGZIP. There is a copy on this CD-ROM. Thiscan be found in the top directory of this CD-ROM in the GZIP folder underMac.

3. "Import" the Arc/Info export filesusing the grid option.

Data Collection

Mapping of central San Francisco Bay was done inthree different surveys. The first was completed by NOAA between December13 - 16, 1996. The second two were completed by the USGS, January 8 - 9,and February 13 - 17, 1997. All three surveys used a Kongsberg Simrad EM-1000Multibeam System hull mounted to the C&C Technologies' RV Coastal Surveyor.

Processing Steps

1. Bathymetry and backscatter data processed onSilicon Graphic computer using software developed by the Ocean Mapping Group,University of New Brunswick. (see USGS OpenFile Report 98-509, The Bathymetry of Lake Tahoe, California-Nevada)
2. Processed data downloaded to a Sun Sparc Ultra 2, running Solaris 2.5as 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


 Cell Size = 4.000
 Data Type: Floating Point
 Number of Rows= 2337
 Number of Columns = 2130
 Xmin = 545163.239
 Xmax = 553683.297
 Ymin = 4184924.766
 Ymax = 4194272.830
 Minimum Value = -115.400
 Maximum Value = -1.710
 Mean = -27.224
 Standard Deviation = 14.727
 Projection UTM
 Zone 10
 Datum WGS84
 Spheroid WGS84


 Cell Size = 4.000
 Data Type: Floating Point
 Number of Rows= 2559
 Number of Columns = 2263
 Xmin = 544996.711
 Xmax = 554048.711
 Ymin = 4184267.961
 Ymax = 4194503.961
 Minimum Value = 0.00
 Maximum Value =254.000
 Mean = 117.705
 Standard Deviation = 38.857
 Projection UTM
 Zone 10
 Datum WGS84
 Spheroid WGS84

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