USGS OFR98-619: Data File Descriptions

Sidescan Sonar Data File Descriptions

Documentation of the sidescan sonar data format is summarized here. The sidescan data are presented in two different ways to make them available to a broader community of users. They are presented in an unmerged form and as netCDF files.

UNMERGED

In the unmerged form, the header information and the imagery are in separate files which both have the same prefix but different suffixes. The header information is contained in files with a hdr suffix (e.g. t1f01.hdr). These are ASCII files with the following fields:

     Field 1:  Line number

     Field 2:  Year - two digits

     Field 3:  Month

     Field 4:  Day

     Field 5:  Hour

     Field 6:  Minute

     Field 7:  Second

     Field 8:  Latitude in decimal degrees

     Field 9:  Longitude in decimal degrees

     Field 10:  Heading - this is 0 if heading was not logged

     Field 11:  Uncorrected depth in meters

     Field 12:  Corrected depth in meters - corrected for variations of the

speed of sound in water.

The associated sidescan image files that go with the header files have a suffix of ".img" (ie. t1f01.img). These files are 8-bit binary raw images. There is no tagged information identifying their size, but in the individual data sub-directories "unmerged" and "netcdf" of the directories "ecgloria/" and "prgloria/", there are ASCII files titled "filesize.txt" that summarizes the number of lines (NL) and samples (NS) in each file along with start and end time of each file.

NetCDF

The second data form is the netCDF file form that is compatible with the USGS WHIPS sidescan sonar processing software (Paskevich, 1992). A description of the NetCDF format, as implemented within the WHIPS software, is included here.

REFERENCES

Paskevich, V., 1992, Woods Hole Image Processing System Software Implementation: Using NetCDF as a Software Interface for Image Processing: US Geological Survey Open-File Report 92-25, 72p.
Unidata Program Center, NetCDF User's Guide: An Interface for Data Access, v1.11, March 1991, 150p.

U.S. Department of the Interior, U.S. Geological Survey
URL: http://pubs.usgs.gov/of/1998/of98-619/htmldocs/document.htm
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