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2-1
2. OPERATION OF ARPA
2.1 General
The FAR-2805 series with ARP-25 board
provide the full ARPA (Automatic Radar
Plotting Aid) functions complying with IMO
A. 823 as well as complying with the radar
performance in MSC.64 (67) Annex 4.
This chapter describes the operation of
the ARPA. For operation of normal radar,
refer to Chapter 1.
Principal specifications
Acquisition and tracking
• Automatic acquisition of up to 20 tar-
gets plus manual acquisition of 20 tar-
gets, or fully manual acquisition of 40
targets between 0.1 and 32 nm (0.1
and 24 nm depending on initial setting)
• Automatic tracking of all acquired tar-
gets between 0.1 and 32 nm (0.1 and
24 nm depending on initial setting)
Vectors
Vector length: 30 sec, 1, 2, 3, 6, 12, 15,
30 min.
Orientation: True velocity or relative
velocity
Motion trend: Displayed within 20
scans, full accuracy within
60 sacans after acquisi-
tion.
Past positions: Choice of 5 or 10 past
positions at intervals of 30
sec, 1, 2, 3 or 6 min.
Alarms: Visual and audible alarms
against targets violating
CPA/TCPA limits, lost tar-
gets, targets crossing
guard zone (guard ring),
system failure and target
full status.
Trial maneuver:Predicted situation ap-
pears in 1 min after se-
lected delay (1-60
minutes).
2.2 Keys Used for ARPA
The Auto Plotter uses the keys on the plot-
ting keypad on the right side of the radar
screen and two keys on the control panel.
Below is a brief description of these keys.
E-plot is inperable in ARPA mode. For E-
plot reber to section 1.24 and 1.34.
CANCEL: Terminates tracking of a single
target specified by the trackball if the key
is pressed with a hit-and-release action.
If the key is held depressed for about 3
seconds, tracking of all targets is termi-
nated.
ENTER: Registers menu options se-
lected.
VECTOR TRUE/REL: Selects true or rela-
tive presentation of target vectors.
VECTOR TIME: Selects a vector length
of 30 sec, 1, 2, 3, 6, 12, 15 or 30 min.
TARGET DATA: Displays data on one of
tracked targets selected by the trackball.
TARGET BASED SPEED: Own ship's
speed is measured relative to a fixed tar-
get.
AUTO PLOT: Activates and deactivates
the ARPA functions.
TRIAL: Shows consequences of own
ship's speed and course against all
tracked targets.
LOST TARGET: Silences the lost target
aural alarm and erases the lost target
symbol.
HISTORY: Shows and erases past posi-
tions of tracked targets.