Simrad ARGUS FMCW 3G, User Manual

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Basic operation | Argus Radar Operator Manual
4.
Select “Auto Drift” and the speed displayed in own ship window will be the result of the
calculation of the Ref Target relative speed inverted by 180 degrees.
Pressing “Ref Target Sel” with no tracked target, or no target selected or a moving target se-
lected, the system will indicate “Wrong: No Steady Target” in the wrong order area.
Selecting Auto Drift with no reference target, the system will indicate “Wrong: No Reference
Target” in the wrong order area.
Also, this kind of speed source is not allowed if AIS is ON.
When the speed source is the reference target, the value is calculated filtering the difference
of relative position between the reference target and own ship. Consider that the position
precision is proportional inverse to distance because the measurement in azimuth depends
of the radar antenna beamwidth multiplied by the range.
Good reference target speed is obtained from acquiring and tracking near echoes with small
area but with good radar reflectivity.
Warning:
The echo used as reference must be a stationary target, otherwise all speed
calculated will not be true, but only relative to the reference target. It is wrong to select a
ship that is anchored as a reference; no alert will be signalled when the ship starts to move
and all the calculated true speed will change to erroneous values. The reference echoes
should never be used to calculate relative speed. This data is not following a speed change
with adequate accuracy for an anti-collision system.
Warning:
When the reference target is lost, the speed source will automatically be
switched to LOG. If the LOG is working on water track, the speed mode will become sea
stabilised.
EPFS speed
Selecting the EPFS speed, own ship’s speed is taken by the speed information coming from
the connected positioning source (i.e. GPS). The sentences accepted on the EPFS serial port as
source of speed are VTG and RMC.
When an EPFS is used as speed source, that speed is calculated filtering the variation of the
position of the ship. Considering that EPFS position resolution is around 10-20 m, and the
speed measured is less than 1 KN, the course inaccuracy will increase with decreasing speed.
In case none of the above sentences are available from the EPFS, but the system is connected
to an AIS receiver, the EPFS source speed can be given from the VDO sentence of the AIS. In
this last case the “EPFS Speed” labelled button changes to “AIS Speed”.
Choosing the EPFS speed, with any of the above sentences, the speed and course values are
handled as if they came from a Ground Stabilized Dual Axis Speed Log, and the label next to
the speed and course values in own ship window change to “STW” and “Crs”.
If any of the above sentences are available, the values of the usable speed and course are dis-
played in the labels placed to the right of the “EPFS Speed” labelled button and their validity is
displayed there as well.
Valid EPFS Speed and Course
No EPFS Speed Information
Not Valid EPFS Speed and Course
Valid AIS Speed and Course
System EPFS
Using the manual speed or a single axis speed log, it is also possible to enter a Manual Drift,
pressing the Manual Drift On/Off button and entering the correct values in the labels next to
it. The way to enter the values is exactly the same as for entering manual speed.
Using the EPFS Speed or a Dual Axis Speed Log the “Manual Drift” button is disabled.