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August 2020 – TD 316 OPERATING MANUAL – Motus Wave Sensor 5729
3.10.4
Buoy Settings
Figure 3-28: Buoy Settings in User Maintenance
If the sensor is positioned off-center you will be able to compensate for this offset by enabling
Enable Off-center
Correction
. The sensor will then use the xyz coefficients given in
Off-center XYZ (m)
to compensate for any off-center
positioning. Refer to
chapter 2.3
for calculation of the off-center coefficients. Sea trials indicate that the error introduced
when not compensating for this effect can be in the order of 10 -15 % (40cm installation offset) depending on the sea
state and spectral distribution of the waves.
If
Enable Frequency Correction
is set then
Correction Frequencies (Hz)
and
Correction Factors
are enabled and
used in calculations.
Correction Frequencies (Hz)
set a total number of 15 frequencies and each frequency has a
corresponding
Correction Factors.
These setting are used to correct for different frequency response of different
buoys. The default settings are according to the Motus DB 1750 buoy and can also be used for similar buoys. If you
want to use the sensor on another buoy with different frequency response then please contact
Sensor Rotation Offset PRH (Deg)
sets a compensation value for
Pitch
,
Roll
and
Heading
. These values is added to
the IMU calculated Pitch, Roll and Heading. These values do not change the calculated wave direction, but only the
output parameters
Pitch
,
Roll
and
Heading
. When post processing the wave directions using an external compass as
reference these values must be subtracted from the Sensor Orientation before the External compass corrections are
performed.
Enable Magnetic Declination
is normally used when sensor is used close to South Pole or North Pole.
Declination
Angle (Deg.M)
is a value to correct for the magnetic variation on the site where the sensor is used. This is the angle in
degrees between magnetic north and true north.
Magnetic declination (variation) is the angle between the magnetic
north and the true north. This angle varies depending on the position on the Earth’s surface and also varies over time.
Declination is positive when magnetic north is east of true north and negative when it is to the west (input angle value
±180°). Magnetic declination at the deployment location can be found for i.e. on NOAA website:
http://www.ngdc.noaa.gov/geomag-web/
