POS MV V4 User Guide
Introduction
Copyright © Applanix Corporation, 2009
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5 to 30 minutes to complete. The time taken to complete this process will
depend on the latitude and on the manoeuvres that the vessel performs
during the operation.
A more accurate and rapid alignment will occur if the vessel performs a
number of calibration manoeuvres during the alignment process. These
manoeuvres consist of full turns, starts and stops, S-curves and figure-of-
eight turns.
After alignment, the IMU delivers measurements of its heading with respect to
true north. These are accurate to between 0.2° and 2.0°, depending on the
manoeuvres made by the vessel and its latitude. Manoeuvres that are more
frequent will yield a more accurate heading result, while operation in higher
latitudes will degrade the unaided heading accuracy.
POS MV rotates the IMU heading measurement, using the relative mounting
angles between the IMU, the vessel, the transducer and your chosen
reference frame, and delivers heading measurements valid for the multi-beam
transducer and the vessel.
Operation with GAMS
Figure 3 and the following paragraphs describe how POS MV computes
heading with GAMS heading aiding.
After power-on, and the Initialization and self-test routines have finished, the
IMU performs a levelling routine to establish a locally level reference frame.
This occurs rapidly and usually finishes within 30 seconds.
Following its levelling routine, the IMU begins to align itself to true north. This
gyrocompassing process is aided by the heading input from GAMS and is
completed within two to five minutes, depending on how long it takes GAMS
to come online.
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