11.3.3 Pitch Test
The pitch data collection is over the same type of sea floor as the latency data collection, i.e. steep
slope or feature on the sea floor. One line is surveyed, twice, in reciprocal directions at survey
speed. It is very critical that the sonar head passes over the same exact part of the slope on each
run.
A profile of the data will show two different slopes,
which represent the reciprocal data collections. The
patch test software goes through a series of
iterations of pitch angle corrections until the
difference between the two surfaces reaches a null.
Whatever the angle of correction, which results in
the minima or null, that angle will be reported as the
pitch misalignment.
A pitch error will result in a an along –track position error, which increases greatly with depth
Graph 2: Position errors as a result of pitch misalignment; error can be either negative or positive
0
1
2
3
4
5
6
0 100 200 300 400
Sounding Position Error (metres)
Water Depth (metres)
Position Errors due to Pitch
Alignment Errors
1.0° Error
0.75° Error
0.5° Error
0.25° Error
Figure 134: Pitch data collections
Page 134 of 210
Version 5.0 Rev r002
Date 05-08-2014
Part No. 96000001
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