JRC JMA-9832-SA Instruction Manual page 188

Attention
There are the following limitations on use of the target acquisition and tracking
functions of ARPA:
Use these radar only as assisting device for navigation.
The final decision for navigation should made by the officer himself.
[ 1 1 ] Resolution between adjacent targets and swapping during
automatic tracking
Depending on the particular distance and echo size, resolution between adjacent targets
during automatic tracking usually ranges somewhere between 0.03 to 0.05 nm. If
multiple targets approach each other, resolution will become about 0.03 nm and this
may cause the system to regard them as one target and thus to swap them or lose part
of them. Such swapping or less of targets may also occur if the picture of the target
being tracked is affected by rain/snow clutter returns or sea clutter returns or moves
very close to land.
[ 2 2 ] Intensity of echoes and the tracking function
The intensity of echoes and the tracking function have a correlationship, and thus the
target will be lost if no echoes are detected during six scans in succession.If a lost
target exists, therefore, radar gain must be increased to support detection of the target.
If, however, radar gain is increased too significantly, sea clutter returns or other noise
may be erroneously detected and tracked as a target, and resultingly, a false alarm may
be issued. In such a case, radar gain must be reduced to suppress the noise.
[ 3 3 ] Adverse effects of error sources on automatic tracking
To execute accurate tracking, it becomes necessary first to appropriately adjust the
[GAIN], [SEA] and [RAIN] controls of the radar so that the target to be acquired and
tracked is clearly displayed. Inappropriate settings of these controls reduce the
reliability/accuracy of automatic tracking.
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