Triton TritonMap - Manual (Page 126)

June 2004 DelphMap™ User's Manual
FIGURE 54. From Map Layout dialog to a resulting view of imagery
Seeing Differences Between Two Similar Files
Suppose you conduct a data survey and then you survey the same area at a later time.
Usually you want to know if there are any differences in the two surveys. Maybe new objects
have been added or removed from the area. Or maybe you have the same objects in two
mosaics, but they have changed locations or orientation. Or maybe the relationship of the
seafloor to the sea surface has changed. DelphMap has two tools to help you find and assess
these differences. In DelphMap, file differences can be computed from two two-dimensional or
two three-dimensional files.
The first tool compares two DDS_VIF files as an “A-B” comparison, where one line is
subtracted from another, revealing their differences in a third DDS_VIF file. Ideally, the files
that are being compared should be two side scan sonar data files. (Although there’s nothing to
prevent you from doing an “A-B” comparison of two bathymetry DDS_VIF files, the better tool
for comparing bathy data is DelphMap’s volumetric computation tool, which is designed for
working with bathy files.)
Chapter 7: Printing and Comparing 112