Making an ‘a b’ comparison, Making an ‘a-b’ comparison – Triton TritonMap User Manual
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June 2004 DelphMap™ User's Manual
Volumetric computation computes the volume from two DDS_VIF bathymetry files and puts
the results in a third DDS_VIF file containing the differences between the two compared files.
This is the second comparative tool available in DelphMap. These differences show up on
your screen as color-coded images extracted from the differences in values between the
compared files. Because volume is three-dimensional, the files used in volume computation
must be bathymetry files, not sidescan files.
Making an ‘A-B’ Comparison
To make a valid “A-B” comparison, you must use the same method and approach in
gathering data for the two surveys. Obviously, you must conduct your second survey over
the same area that you did for the first survey. Less obviously, you should use the same
range scales, and your towfish should be operating at the same altitude while recording
each mosaic.
To compute A-B differences between two similar files
1. Open an existing project or create a new one.
2. Into the open project insert two layers representing two similar but possibly
different DDS_VIF files (lines).
An example of such a pair of lines is shown in Figure 55.
Chapter 7: Printing and Comparing
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