Kongsberg Seatex Seapath 200, Installation Manual

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Seatex Seapath 200 Installation Manual, rev. 13 Installation
36
The reference for roll and pitch calibration must be carefully selected depending on the
intended application. It may be the hull, or a sensor like a multibeam echo sounder or a USBL
acoustic system. Some sensors have internal calibration routines, and accurate calibration of
the MRU is not required. In "Appendix D - Seapath configuration software, SCC" a procedure
for automatic setup of MRU mounting angles is described.
An accurate alignment of the MRU +R arrow with respect to the vessels longitudinal axis
(yaw orientation) is of crucial importance. If not properly aligned, the performance of the roll
and pitch measurements from MRU will be degraded. The easiest way to ensure a correct yaw
orientation of the MRU is to mount the unit on the vessel's longitudinal or transversal
bulkheads. Figure 17 illustrates that a misalignment of 1 degree of the MRU in yaw will result
in a roll error of
±
0.09 degrees if the vessel is pitching
±
5 degrees. To calibrate the
misalignment of the MRU axis to an accuracy of 0.5 degrees is not an easy task and requires
use of an accurate external reference.
-10 -5 0 5 10
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
pitch-angle [deg]
ro
ll-
er
ro
r [
deg]
Misalignment about yaw-axis
1 deg
2 deg
Figure 17 Value of roll-error as function of vessel pitch angle as parameter and 1
°
and 2
°
yaw misalignments