Northrop Grumman Sperry Marine VisionMaster FT, User Manual

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Radar/Chart Radar User Guide Targets
65900010 10-31
Tracked targets are dropped automatically if they meet all of the following
criteria:

The target is not in an auto-acquisition zone.

The target is not currently selected for display in the Target tote.

It does not infringe the CPA/TCPA or BCR/BCT alarm criteria.

It is fully established i.e. it has a motion trend vector displayed.

The TCPA is more than 3 minutes ago.

The target is astern of own ship.

The target’s range is more than the defined auto drop range from
own ship.

The target has not been selected as echo reference.
In addition to the auto-drop mode, tracked targets are always dropped
without an alarm being raised if they meet any of the following criteria:

The target’s range is greater than the maximum tracking range.

No good video data has been extracted for the target for the last 60
scans.

The system has been switched to Standby.
Target Auto Drop on Dual Radar
On dual radar, targets are auto dropped if they meet the following criteria
(in addition to the criteria listed on the previous page):

The target is astern of the transceiver connected to channel 1

The range is more than the defined auto drop range from the
transceiver connected to channel 1
In addition, tracked targets on dual radar are always dropped without an
alarm being raised if they meet any of the following criteria:

The range is more than 40.0 NM from all transceivers in transmit.

No good video data has been extracted by either channel for the
last 60 scans.

Both radar channels have been switched to Standby.