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Doc. P/N:
WSP-009-005
Version: V1.5
Issue Date:
October 2013
www.wassp.com
Page 56 of 73
Installation Manual
(- late / + early ) 2 x delta
(fast speed in knots) - (slow speed in knots)
10.2.6.2
Test 2: For use with DGPS
The advantage of this approach over the previous test is it will eliminate pitch errors, however,
the displacement of the object will be smaller and this will be difficult to measure accurately as
GPS errors can make this impossible.
Approach the distinct feature from the
same direction
at two vastly different known speeds,
as close to zero and at the fastest mapping speed. If the object moves by delta metres further
along the vessel track (+ve) at a faster speed the adjustment to the time delay will be:
delay adjustment =
10.2.7 Sea Trial - Commissioning Step 14 : Patch Test (Roll)
Before attempting a roll patch test it is suggested that the GPS Time lag and any latencies are
accounted for. Also, it is recommend that you conduct a preliminary adjustment of the
Sound
Speed
settings to get things in the correct ballpark. Configure
Navigator
to use
Overwrite
mode when mapping depths so that the full extent of any difference is recorded.
10.2.7.1
Automatic Roll Patch Test (Recommended)
This is available under the
Patch Tests
button on the
Sensor Values
tab in the
Ship Setup
.
The automatic patch test will give instructions as you proceed. The same instructions are
detailed below:
Use the local chart and local knowledge
to identify a spot for the roll patch test –
ideally a flat area between 20-40m.
Once you have 200m+ of clear water in
front of the vessel, click
Start Patch Test
.
Run the ship along a line in one direction
for at least 200m. It may help to run with
the tide and wind behind the vessel as the
return journey is the important one.
The Patch Test window will prompt you
when you have completed the first run.
Turn the ship around, and make a return
journey so that the same area is mapped,
but which the exact
opposite heading
is used. It may help to use the Navigator
Heading Up
and
COG
functions.
While turning, remember to give the vessel plenty of room to be aligned with the
previous track prior to starting the second run.
1
2
3
Figure 50. Patch Test Selection window