POS MV V5 Installation and Operation Guide
Installation
Copyright © Applanix Corporation, 2017
2-29
The multibeam transducer will be some distance from the vessel centre of rotation. The transducer will
therefore experience a small component of heave as the vessel moves vertically in the water and a much
larger component of apparent heave with changes in vessel attitude.
To separate these effects, POS MV translates the IMU measurements to the vessel centre of rotation.
Having done so, it applies filtering to the measurements of pure heave as explained in the Theory of
Operation on page B-1 and then translates the filtered measurements back to the positions of sensors 1
and 2.
This method for measuring heave avoids the errors that can occur if you filter direct heave measurements
made from a point remote from the vessel centre of rotation.
Measure and record the distance from your reference point to the vessel centre of rotation.
•
A positive value for the X lever arm means the vessel centre of rotation is forward of your
reference point
•
A positive value for the Y lever arm means the vessel centre of rotation is to starboard of your
reference point
•
A positive value for the Z lever arm means the vessel centre of rotation is below your reference
point
Antenna Baseline Vector
The antenna baseline vector is the vector describing distance from phase centre of primary antenna to
phase centre of secondary antenna in the vessel frame. If this vector can be determined accuractely
(error <= 5 mm) then the values can be entered into the GAMS parameter setup window and avoid
having to perform a GAMS calibration, which on a large vessel may not be practical or as accurate. If the
antenna baseline vector cannot be accurately determined and the vessel can perform dynamics sufficient
to achieve a good GAMS calibration then the baseline vector parameters can be left as zero.
Mounting Angles
General
Measure and record the mounting angles relative to the reference frame that you have chosen. Resolve
these angles into three rotations that you must apply, in a strictly defined sequence, to align the mounting
angles with your chosen reference frame. The Tait-Bryan sequence of rotations is used.
Tait-Bryan Rotation Sequence
Apply the rotation in the following order to bring the two frames of
reference into complete alignment: