Triton Isis - Manual (Page 203)

June 2004 Isis® Sonar User's Manual, Volume1 189
during the collection of statistics and during the entire survey for which
grazing angle compensation is applied.
It is important to realize that Isis will only calculate a GAC outside of boresite
since distortions inside of boresite are dominated by effects of the beam
pattern. If, therefore, due to the ping rate and the tilt angle of the sonar,
boresite falls outside of the collected statistics for the GAC, the
compensation will be completely flat.
If boresite is beyond the far range of the collected sonar
imagery, Isis will not calculate a GAC.
9.8.4 Applying a Level of Operation to Get an Angle
You must have a waterfall window open and selected before you can have
Isis give you angle corrections. When you choose Beam Angle, Grazing
Angle, the system displays a dialog box for this function.
A typical Beam Angle, Grazing Angle dialog box is shown in Figure 9-17.
Chapter 9: Using the Tools Menu