Arpa Operation; Precautions For Use; Controls For Use With Arpa - Furuno 1835 Operator's Manual

3.

ARPA OPERATION

The Automatic Radar Plotter ARP-11 (option) manually or automatically acquires and
tracks ten targets. Once a target is acquired automatically or manually, a target is au-
tomatically tracked within 0.1 to 16 nm.
3.1

Precautions for Use

CAUTION CAUTION
Do not depend on one navigation device
for the navigation of the ship. The
navigator must check all aids available
to confirm position. Electronic aids are
not a replacement for basic navigation
principles and common sense.
· The ARPA automatically tracks an
automatically or manually acquired radar
target and calculates its course and
speed, indicating them by a vector. Since
the data from the auto plotter depend on
the selected radar targets, the radar must
be optimally tuned for use with the auto
plotter, to ensure required targets will not
be lost or unnecessary targets like sea
returns and noise will not be acquired
and tracked.
· A target is not always a landmass, reef,
ship, but can be returns from the sea
surface and clutter. As the level of clutter
changes with the environment, the
operator must correctly adjust the A/C
SEA, A/C RAIN and GAIN controls so
that the target echoes do not disappear
from the radar screen.
3.2

Controls for Use with ARPA

ENTER: Acquire cursor-selected target. Display data for tracked target (in the data
box at the bottom of the screen).
CANCEL/HL OFF: Remove data of cursor-selected tracked target from the data box.
Stop tracking the cursor-selected target (when its data is not displayed in the data
box).
MENU: Access the [Target] and [ARPA] menus for ARPA operations.
Cursorpad: Select a target to acquire (or cancel the tracking). Select a target to show
(or remove) target data.
CAUTION CAUTION
The plotting accuracy and response of
this ARPA meets IMO standards.
The tracking accuracy is affected by the
following:
· The tracking accuracy is affected by
course change. One to two minutes is
required to restore vectors to full
accuracy after a sudden course change.
(The actual amount depends on
gyrocompass specifications.)
· The amount of tracking delay is inversely
proportional to the relative speed of the
target. Delay is on the order of 15-30
seconds for high relative speed; 30-60
seconds for low relative speed.
The display accuracy is affected by the
following:
· Echo intensity
· Pulse width of radar transmission
· Radar bearing error
· Gyrocompass error
· Course change (your ship or target)
3-1