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1.25 Electronic Plotting Aid (EPA)
10 operator-selected targets can be plotted
electronically to assess their motion trend.
Five past positions can be displayed for each
of the plotted targets. If you enter a 6th plot
on a certain target, the oldest plot (past posi-
tion) will be erased.
A vector appears when you enter a second
plot for the target and is updated each time a
new plot is entered. The vector shows the
target motion trend based on its latest two
plots.
Target data is shown in the data display area
which shows range, bearing, course, speed,
CPA and TCPA of the last-plotted or selected
target.
Target data
Plotting time
000
RNG
010
350
340
020
330
030
BRG
320
040
CRS
TRUE VECTOR
310
050
SPD
1
30sec
See note
CPA
300
060
1
below.
TPCA
2
070
290
00:25
See note
280
080
3
below.
090
270
260
100
250
110
Echo Watch Zone
240
120
230
130
140
220
210
150
200
160
190
170
180
EPA symbols
: Target plotted
: Target plotted and data
indicated.
: Target on a collision course
Note:
Target 2 is on a collision course as the extension
of its vector goes through the own ship position.
Placing the offset EBL will help for assessment.
TCPA is counted up to 99.59 min and beyond
that it is indicated as TCPA > 99.59 MIN.
Figure 1-25 EPA display
Note: The EPA requires speed input (auto-
matic or manual) and a compass signal. The
vector and data are updated on real time be-
tween plot entries, but do not neglect to plot
a new position over a long period of time.
Otherwise, the accuracy will be reduced. Note
that the plots will be lost when the compass
fails; start the plotting exercise again.
Plotting a target
1. Place the cursor on a target of interest by
operating the trackball.
2. Press the [ACQ] key. A plot symbol (circle)
and target number (0-9) appears on the
target.
3. Watching the EPA time shown at the right
side of the screen, wait for at least 30
seconds. Place the cursor (+) on the plot
symbol with number and then press the
[ENTER/SELECT] key. The symbol shape
changes from circle to square and the
target number in the data display flashes.
4. While the target number is flashing, place
the cursor on the target and press the
[ACQ] key. The plot symbol moves to the
new target position and the previous po-
sition is marked by a small dot.
5. To acquire other targets, repeat the above
steps selecting different plot symbols.
6. If the target echo separates from its plot
symbol, repeat steps 3 an 4.
Note: If a target once plotted is not plotted
again within 10 minutes, the warning “UP-
DATE PLOT” and Plot No. will appear on the
upper right margin of the screen and the plot
symbol of the target flashes. If you want to
continue plotting this target, reacquire it within
five minutes. Otherwise, the target will be re-
garded as a “lost target” and its plot symbol
and target data will be erased. The larger the
plotting interval, the less accurate the plot-
ted target data. Plotting of each target should
normally be made every 3 or 6 minutes as
far as possible. You can use the Time Alarm
to warn yourself every 3 or 6 minutes.
Within 30 seconds, you can cancel a last plot
by the [CANCEL/CLEAR] key and make a
re-entry at a different position. After 30 sec-
onds, the last entry is processed to produce
a vector.
1-19
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