Prerequisites
NoteBefore you do this task, you must adjust the installation offset of the motion sensor.
The ST90 system has been set up with its hardware units connected as specified in the Installation Manual.
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The external motion sensor is connected to the ST90 system. |
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The ST90 system is turned on and operates normally. |
NoteWe recommend that you do this task in calm sea without any vessel movements.
Context
It is very important that the motion sensor is set correctly with stabilization offset values that
are adapted to the physical installation angles of the hull unit. Even a small offset error can give you very inccurate readings. In many cases a suitable motion sensor is already installed. This sensor may be mounted anywhere on the vessel. Because of this, the risk of stabilization offset misalignment is present.
The two screen captures below illustrate how the ST90 system can provide inaccurate data if the stabilization offset is misaligned. In both examples, the
tilt is set to approximately 24 degrees, and you are looking at the echoes from a flat
bottom at a very short range. The first example is made without any offset errors, and the echoes
from the bottom are evenly distributed in the circle. On the second screen capture, a 3 degrees roll
offset error causes the echoes to be "distorted". This error will of course be more visible on
longer ranges.
NoteDo not confuse stabilization offset with installation offset. The installation offset values describe the physical location and orientation
of an item, and how this location is related to the vessel's
coordinate system. The stabilization offset values describe any misalignments related to the measurements a sensor make.