User's Manual Part 2

Operator Manual
3−16
3748DOC020102 Edition: 14.JAN.2005
3.4.1.3 Plotting
Plotting is started by positioning the trackball cursor over the desired target
echo. When the softbutton is pressed the radar aquires the target.
When a target becomes too weak or too large and is identified by the ARPA as a
LOST TARGET, two options are available:
(1) CANCEL Option: As a warning, a flashing symbol marks the last position of
the target. The ARPA attempts the target by increasing the window size.
It coasts for five scans (antenna rotations) and if the target is not located in
the enlarged window, the plot is cancelled.
(2) COAST Option: The lost target data is not automatically cancelled but
rather is “coasted “ and the flashing LOST TARGET symbol marks the last
position of the target. To delete the LOST TARGET symbol, track, and tar-
get data, a manual cancel operation must be done.
CAUTION
IF A TARGET GETS CLOSE TO ANOTHER TARGET, THE TWO TAR-
GETS CANNOT BE DISCRIMINAT AND TRACKING MAY RESUME ON
THESE SIGNALS.
THE OPERATOR SHOULD INVESTIGATE ALL ARPA ALARMS.
Occasionally, when a vessel changes course while coasting or other targets are
in the vicinity, a plot may be lost or transferred to another target. The flashing
alerts the operator to verify the condition after coasting.
NOTE
If a plot acquisition is attempted on a target close to another plot,
the new plot will be refused.