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

        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 (ie.
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

        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 with them identifying their size,
but in the "unmerged" directory is an ASCII file titled "filesize" that
summarized the number of lines (NL) and samples (NS) in each file along
with start and end time of each file.

        The second data form is the netCDF file form that is compatible
with the USGS WHIPS sidescan sonar processing software (Paskevich, 1992).

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.