Kongsberg EM 122, Руководство по установке

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alignment
The latter point is recommended if the sensor is used for other purposes than just the
multibeam, or if its accuracy is sensitive to horizontal acceleration.
If there is any point in the fore-aft direction which does not change height with respect
to the water line with changes in vessel speed, this will be the ideal location for the
motion sensor as it will eliminate any errors from squat induced height changes which is
not measured by current motion sensors.
Heading sensor
This sensor can either be based upon:
• GPS measurements like Seapath 300 or POS/MV
• Fibre optic gyro compass
• Standard gyro compass
The heading sensor dynamic accuracy should be in the order of one third of the transmit
transducer beamwidth or better (i.e. 0.3º for a 1º beamwidth).
The sensor must be aligned to the vessel centre line to provide an accuracy better than a
fifth of the transmit transducer beamwidth (i.e. 0.2º for a 1º beamwidth).
Compasses sensitive to acceleration should be mounted close to CG (Centre of Gravity)
Please see the sensor installation manual for any further instructions on installation
and alignment.
The output of the sensor must be verified with the vessel having a known heading such
as when it is in drydock. Alignment accuracy can also be evaluated with the vessel tied
(in opposite directions) along a quay with known heading. A calibration survey should
afterwards be performed at sea to confirm correct performance.
Positioning system
Most positioning systems are today based on Global Navigation Satellite System
technology (GNSS) such as GPS, GLONASS and/or (later) GALILEO. The location of
the positioning system, antenna must be measured, including its height (if geoide height
is a measured and used parameter). It should be noted that some GNSS based systems
use two (or more) antennas to provide vessel heading, if so the installation manual
for the system should be consulted for how these antennae are to be aligned and how
accurately the location of the antennae need to be measured.
Water line
With the vessel in normal trim, i.e with an indicated pitch angle of zero from the motion
sensor, the distance to the waterline may be measured anywhere on the vessel. Otherwise
it must be measured at the alongship physical location of the motion sensor. The
measurement should be taken on both sides of the vessel and averaged to remove any
roll effects. Simultaneous measurements are required if the vessel is moving.
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