3. TARGET TRACKING (TT)
3-16
3.12
Vector Modes
Target vectors can be displayed relative to own ship’s heading (Relative) or North
(True).
Note:
IMO recommends the use of true vector mode in sea stabilization or relative
vector mode for collision avoidance.
3.12.1
Description of vectors
Stabilization modes
It is important to select the optimum stabilization mode for the radar display. To assess
risk of collision the relative motion of a target gives the clearest indication of CPA and
may be monitored by observing either the direction of the target's relative trail, or the
CPA predicted by the relative vector. By default, relative motion displays relative target
trails and true motion displays true target trails. Where true target trails is selected, a
sea stabilized display will indicate all targets' motion through the water. A ground sta-
bilized display will indicate all targets' motion over the ground.
In coastal, estuarine and river waters where a significant set and drift may be experi-
enced, a sea stabilized display will produce significant target trails from all fixed (sta-
tionary) objects possibly producing an unacceptably high level of clutter and masking.
In such circumstances a ground stabilized display may reduce its effect and enable
the observer to detect clearly the trails of moving targets, thus enhancing the observ-
er's situational awareness.
However, the display should be considered only as an approximation of the course
and speed made good over the ground. Among other factors, the accuracy of the
ground-stabilization is affected by inaccuracies in speed and heading inputs as well
as radar measurement imprecision and will require the display to be readjusted peri-
odically. The information displayed should be interpreted with due regard to these fac-
tors.
Note:
It should be noted that in determining a target's aspect by radar; the calculation
of its true track is dependent on the choice and accuracy of the own ship's course and
speed input. A ground-stabilized target plot may accurately calculate the ground track
of the target, but the target's heading may be significantly different from its track when
experiencing set, drift or leeway. Similarly, a sea stabilized target plot may be inaccu-
rate when own ship and the target, are experiencing different rates of set, drift or lee-
way.
Summary of Contents for FAR-2218
Page 132: ...1 OPERATIONAL OVERVIEW 1 110 This page is intentionally left blank ...
Page 176: ...3 TARGET TRACKING TT 3 36 This page is intentionally left blank ...
Page 202: ...4 AIS OPERATION 4 26 This page is intentionally left blank ...
Page 232: ...5 VIDEO PLOTTER OPERATION 5 30 This page is intentionally left blank ...
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