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3. ARP OPERATION
3-17
3.9 Vector Modes
Target vectors can be displayed relative to own ship's heading (Relative) or north
(True).
3.9.1 Description of vectors
Ground stabilization and sea stabilization
Target vectors can be ground stabilized or sea stabilized. Sea stabilization is a
mode where own ship and all targets are referenced to the sea using a compass
heading and single axis log water speed inputs in the True Motion mode. Ground
stabilization is a mode where own ship and all targets are referenced to the
ground using the ground track or set and drift inputs. If the accuracy seems
unsatisfactory, enter the set and drift correction. Note that set and drift should
not be used when the radar is displaying AIS targets.
True vector
In the true motion mode, all fixed targets such as land, navigational marks and
ships at anchor remain stationary on the radar screen with vector length zero.
But in the presence of wind and/or current, vectors appear on fixed targets
representing the reciprocal of set and drift affecting own ship unless set and drift
values are properly entered.
Target on
collision
course
Own ship
Buoy
Own ship
Target on
collision
course
Buoy
True vectors in
head-up mode
Relative vectors in
head-up mode
True and relative vectors
Relative vector
Relative vectors on targets which are not moving over the ground such as land,
navigational marks and ships at anchor will represent the reciprocal of own
ship’s ground track. A target of which vector extension passes through own ship
is on the collision course. (Dotted lines in the figure are for explanation only.)