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4. Tracked Target (TT) Operation
4-12
4.9 Vector Modes
Target vectors can be displayed relative to own ship's heading (Relative) or north (True).
4.9.1 Description of vectors
Ground stabilization and sea stabilization
Target vectors can be ground stabilized or sea stabilized in the True Motion mode. You can select ground or sea
stabilization from the speed selection dialog box. Select BT(Bottom Tracking) for ground stabilization or WT(Water
Tracking) for sea stabilization. The TT VECTOR box shows the stabilization mode in the true motion as T
VECT(G) or T VECT(S).
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 set and drift corrections. 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, the vectors appear on fixed
targets representing the reciprocal of set and drift affecting own ship unless set and drift values are properly entered.
In the true vector mode, there are two types of stabilization: ground stabilization (T VECT(G)) and sea stabilization
(T VECT(S)). The stabilization mode is automatically selected according to speed selection, as shown in the table
below. For speed selection, see section 2.5 How to Input Your Ship's Speed.
Speed selection True vector mode
LOG(WT) T VECT(S)
LOG(BT) T VECT(G)
POSN T VECT(G)
REF T VECT(G)
MAN T VECT(S)
MAN w/set & drift T VECT(G)
Relative vector
Relative vectors on targets that 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 whose vector passes through own ship is on a
collision course. (Dotted lines in the figure are for explanation only.)
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