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2-12
Displaying and erasing past
positions
To display past positions, press the
HISTORY key to display past positions of
targets being tracked. The label HISTORY
appears at the upper-right corner of the
screen.
ORIGIN
MARK
VECTOR
TRUE/
REL
VECTOR
TIME
TARGET
DATA
TARGET
BASED
DATA
AUTO
PLOT
TRIAL
LOST
TARGET
HISTORY
To erase past positions, press the HIS-
TORY key again.
Selecting the number of dots and
past position plot intervals
1. Press the E, AUTO PLOT MENU key
on the plotting keyboard to show the
ARPA 1 menu.
Hit [E, AUTO PLOT MENU].
1 AUTO ACQ
2 AUTO ACQ AREA
3 GUARD RING
4 GUARD RING SET
5
6 CPA, TCPA SET
7 HISTORY POINTS
8 HISTORY INTERVAL
0 [ARPA 2]
OFF/ON
6 NM/SET
OFF/ON
CPA 00.0NM
TCPA 00.0MIN
5/10/20*
30S/1/3/3/6MIN
*5/10 only on IMO-type
[ARPA1]
2. Press the [7] key to select menu item
7HIST ORY POINTS.
3. Further press the [7] key to select a de-
sired number of past positions (5, 10,
20, 30, 100, 150 or 200). The IMO-type
has the selection of only 5 or 10.
4. Press the ENTER key to confirm your
selection.
5. Press the [8] key to select menu item
8HIST ORY INTERVAL.
6. Further press the [8] key to select a de-
sired past position plot interval (30 sec-
onds, 1, 2, 3 or 6 minutes).
7. Press the ENTER key to conclude your
selection.
8. Press the E, AUTO PLOT MENU key
to close the menu.
2.12 Setting CPA/TCPA Alarm
Ranges
The ARPA continuously monitors the pre-
dicted range at the Closest Point of Ap-
proach (CPA) and predicted time to CPA
(TCPA) of each tracked target to own ship.
When the predicted CPA of any target be-
comes smaller than a preset CPA alarm
range and its predicted TCPA less than a
preset TCPA alarm limit, the ARPA re-
leases an aural alarm and displays the
warning label COLLISION on the screen.
In addition, the ARPA symbol changes to
a triangle and flashes together with its vec-
tor.
Provided that this feature is used correctly,
it will help prevent the risk of collision by
alerting you to threatening targets. It is
important that GAIN, A/C SEA, A/C RAIN
and other radar controls are properly ad-
justed.
CPA/TCPA alarm ranges must be set up
properly taking into consideration the size,
tonnage, speed, turning performance and
other characteristics of own ship.
CAUTION
CPA/TCPA Alarm
The CPA/TCPA alarm feature should never
be relied upon as the sole means for detect-
ing the risk of collision.
The navigator is not relieved of the respon-
sibility to keep visual lookout for avoiding
collisions, whether or not the radar or other
plotting aid is in use.