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Water Temperature
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The water temperature and salinity affect the sound speed and thus the angle at which the sound moves
through the water column. This causes the seafloor to curve up or down as noted on page 48. If the sea-
floor exhibits a curve up or down on the edges, adjust the sound speed. Note: The surface water tempera-
ture will probably change during the course of a day.
Tide Correction
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Tide correction is essential for matching up overlapping swaths. If you have disabled the Tide correction
(see "Tides Tab" on page 51), the swaths will rarely line up on your WASSP displays. Ensure that the ZDA
sentence is being collected and sent to the WASSP Processor so it can determine the UTC time and use the
correct tide compensation value.
Transducer Offsets
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The transducer, GPS and draft offsets need to be input into the WASSP ship setup configuration so that the
motion-induced errors in the seafloor can be correctly compensated for.
Roll Offset
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If there is a fixed offset in the mounting of the transducer or Motion Sensor you will need to conduct a
patch test to determine this error. Without this, the roll correction will not work correctly.
9.13 Why does the seafloor move if the system is motion compensated?
The acoustic views are only compensated for vessel roll to save on processing time and to avoid
creating artefacts in the data. If the Sonar display is rotating with the vessel, then the roll correction is
not working. Remember too that if the vessel is operating in a high sea state, your motion sensor may
not be able to fully compensate for the vessel's movement.
Check roll information is being received
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Open the Sensor Data Tab of the Raw Info window and check that a roll signal is being read by the WASSP
system (see "Sensor Data Tab" on page 40 for more information). You should see an orange line on this
display if the roll information is being processed.
Check that the device that you receive roll information from is on and that all your serial cables
►
are still connected to your WASSP Processor.
Check that the correct sensors are selected in the Ship Setup, this configuration could have been
►
inadvertently changed.
Check that the Roll Configuration settings have not been changed.
►
If the transducer has been re-installed, the Swap Array setting could have changed in which case you will
need to invert the Swap Roll setting. If the roll offset is incorrect, a slight roll of the display will occur. If the
Swap Roll setting is incorrect you will see a doubling of the actual vessel roll (i.e. the roll received when Roll
Correct is disabled).
Finally if the seafloor is not uniformly flat you could see rapid changes in the sonar display with
►
each ping as the ship moves across the seafloor. As there is no heave or pitch compensation on
this display it will often move up and down and if the seafloor changes angle it will also appear
to roll a bit. If you are unsure, check that the seafloor remains flat on a flat piece of seafloor and
remember that a vertical shift is expected if there is vessel roll, pitch and or heave. These artefacts
should be mostly removed when you look at the charting displays which is corrected for the
measured attitude elements.
Doc. P/N:
WSP-009-008
Version:
V1.3
Issue Date:
April 2014
Fre qu e nt ly Aske d Q ue s ti ons (FAQ s )
www.wassp.com
Operator Manual
65
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