4. AIS OPERATION
4-11
4.9 Past Position Display
The past position display shows equally time-spaced dots marking past positions of
activated AIS targets. A new dot is added at preset time intervals until the preset num-
ber is reached. If a target changes its speed, the spacing will be uneven. If it changes
course, its plotted course will not be a straight line.
Below are examples of past position displays.
4.9.1 How to adjust the past position plotting interval
The plotting interval determines how often the target’s past position is refreshed. To
change the plotting interval do the following:
Place the cursor on the plotting interval for the [Past POSN] indication in the [TT•AIS]
box, then press the left button to cycle through the intervals.
The available options, in order, are:[OFF] o [30 SEC] o [1 MIN] o [2 MIN] o [3 MIN]
o [6 MIN] o [OFF]...
To erase all past position points and disable the past position display, select [OFF].
4.9.2 How to select the number of past position points to be dis-
played
1. Open the [MAIN MENU].
2. Select [TT•AIS], then push the ADJUST knob.
3. Select [TT•AIS SYMBOL], then push the ADJUST knob.
4. Select [TT•AIS PAST POSN POINTS], then push the ADJUST knob.
5. Select [5] or [10] as appropriate, then push the ADJUST knob.
6. Close the menu.
4.9.3 Past position display orientation
Past position orientation, true or relative, is controlled with [TRAIL MODE] in the
[TRAIL] context menu. To adjust the trail orientation, see paragraph 1.36.1.
4.9.4 Stabilization in true motion
True motion past position display can be ground stabilized or sea stabilized. The
[TRAIL] box shows current stabilization as "TRUE-G" or "TRUE-S". To change stabi-
lization mode, open the [SHIP SPEED MENU] menu and set [SHIP SPEED] to
[LOG(BT)] (ground stabilization) or [LOG(WT)] (sea stabilization).
(a) Ship turning (b) Ship running straight (c) Ship reduced speed (d) Ship increased speed
Past POSN indication
Plotting interval
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