R2Sonic 2026, Руководство по эксплуатации

Страница: 172 / 254

Page 172 of 254
Version 6.3 Rev r012
Date 05-11-2022
Part No. 96000001
11.8.2 Individually solving values
No matter what the solving order may be, each value should be computed independently. All
tests should be based on the mean of the previous test(s).
It is important to understand why a certain solving order is used in all survey software. Each
computation is based on the previous test result. This is the reason that latency is computed
before pitch and roll are computed before heading; the primary test (latency or roll) has a large
influence on the result for the second test (pitch and heading). The roll computation can also
have an influence on the pitch computation, primarily if the position of the sonar head, of the
reciprocal runs, was not coincident. The heading offset will also have an influence on the pitch
computation for the same reason.
Generally, multibeam surveys are conducted with very accurate time synchronisation using GPS
time and the Pulse Per Second. In this case, the latency test is used to prove the lack of latency
or that is sufficiently small enough to be of no consequence. Using accurate timing, it is not
necessary to collect more than two latency collections. This paper will concentrate on the
angular offset computations. However, if accurate timing is not used, there should be the same
number of collections as with the other tests.
With a good number of individual tests, solve for one computation (i.e., only roll) and derive a
mean and standard deviation for that one test. Determine if the standard deviation is within
acceptable accuracy requirements, then use that derived mean to solve for the next
computation (i.e., pitch). As an example, using the results on page 7, the first step would be to
solve for Roll first, derive a Roll mean and then use that mean in all of the Pitch computations.
Find the mean and standard deviation for Pitch. Use the mean Roll and Pitch values to
determine the Heading offset.
In the above example, the roll mean, of the five tests, is 0.74°, with a standard deviation ( δ ) of
0.01°. The roll mean would now be used when determining the value for pitch. Use the roll
mean and solve all of the pitch computations; the pitch mean is -0.91° (excluding the out of
norm value),
δ = 0.13°. The roll and pitch computed means are now used to solve for the
heading offset. The solved heading offset is 0.92°, δ = 0.08°.
If the heading offset had been 1.5° or greater, it would be advisable to re-compute the pitch
offset, using the computed heading offset value. This is due, again, to the fact that if the sonar
head did not track the same exact position in the reciprocal runs, the heading offset would
have an influence on the pitch offset result.
11.9 Truthing the patch test
After deriving the values for roll, pitch, and yaw, the values should be entered into the
appropriate areas in the data collection software. Ideally, find a singular object that can be
boxed in (running data collection lines, on all sides of the object) and process the data. The
object depiction, with all survey lines, should not vary from the object depiction from any one
line