Triton Bathymetry - Manual (Page 41)

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except in the center where the wreck is located. It is important that the user examines
the places where multiple hypotheses were identified to verify CUBE selected the correct
one.
8.4 Bathy A-B
The Bathy A-B tool allows the user to subtract one bathy grid layer (DTM and CUBE grids)
from another to identify differences in the depth value at each grid node. The output of
the A-B process is a Perspective DTM grid file, with a resolution matching the “A” grid
layer that was used to subtract the “B” layer from.
The A-B process can be launched from either the toolbar button shown right or
from the file tree. Using the toolbar button allows the user to draw a region on
the map display for input into the A-B process. When the toolbar is selected, defining a
region in the map display
will use the top bathy grid
layer visible as the “A”
layer with a dialog that will
popup for the user to select
the “B” layer.
Selecting the A-B option
from the file tree will
subtract an entire grid
layer from another, unlike
the toolbar button which only performs the A-B calculation within a defined region in the
map view.
There are several applications of the A-B tool in Perspective, a few of which are described
here.
1. Object Detection: For ports and harbors, using the A-B algorithm can quickly
identify objects that were not present during the previous survey.
2. Reservoir Sedimentation: Can identify the reservoir capacity loss due to
sedimentation along the dam wall.
3. Sandbar Migration: Useful for monitoring sandbar migration in rivers.