JRC JMA-9832-SA Instruction Manual page 202

Relative Vector Mode
In displaying the relative vector of a target, press the [TRUE/REL] switch to select the Relative Vector
mode.
The relative vector does not represent the true motion of the target, but its relative relation with own
ship. This means that a target with its relative vector directed to own ship (passing through the CPA
LIMIT ring) will be a dangerous target.
In the Relative Vector mode, it can be seen at a glance where the CPA LIMIT of the dangerous target is.
Therefore, the TRUE/REL mode shall optionally be used for the purpose of observation: the TRUE
vector mode for grasping the true aspect of a target, and the REL vector mode for grasping a target's
closest point of approach (CPA).
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