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12 Radar Systems of Maritime Transport
When yawing or changing the heading of own ship, the OK changes its position
within (345–0–15°), returning, each time by a jump to zero of azimuth scale when
reaching the extreme positions. The advantage of this mode is orientation of the radar
image in accordance with the situation observed along the course of the vessel, stabilization of the radar image in the direction. It is recommended to use the orientation
mode “Course STabilized” when following in narrow corners and along coastlines.
In the NORTH orientation mode, the north direction (OC) is always upwards at
zero mark of azimuth scale, and the heading mark (OK) indicates the direction of
the ship, i.e. the ship’s gyrocompass heading. When the course changes, the position
of the target blips on the indicator screen remains unchanged, and the OK position
changes in accordance with the current course of the vessel. BH shows the true
bearing to the target blip. The advantage of this mode is orientation and stabilization
of the radar image in the north direction in accordance with the navigation charts,
but comparison with the real picture observed along the ship’s course is difficult.
The station can display the radar image on the indicator screen in relative or true
motion modes. In the relative motion (OD/RM) mode, the sweep center is stationary,
and in the true motion (ID/TM) mode, the sweep center moves according to the
data from the stabilization sensors measuring own ship’s speed (as a vector), and
after passing through 2/3 of the screen radius, it automatically returns to the point
opposite to the direction of motion and continues to move in accordance with the
data from the stabilization sensor.
Radar plotting. Automatic radar plotting (ARP) operates only in stabilization
modes NORTH and COURSE ST from gyrocompass. To manually lock-on a target
for auto-tracking, it is necessary to place the cursor (not necessarily exactly) on the
selected target and press the LOCK-ON button. The criterion for lock-on (taking
a target for auto-tracking) is the condition of detecting the target at least twice in
three surveys, while the target will have a symbol (dotted square) starting the AC
(auto-tracking) operation.
If the lock-on has occurred, then no later than 30 s, and the target must have a
target movement and approaching vector: range, bearing, course (heading), speed,
distance of shortest approach (DSA), time of shortest approach (TSA), distance to
course intersection point (DCI), time to course intersection point (TCI).
Guard zone—the zone of targets auto-lock-on for auto-tracking (target acquisition) is activated through the AUTO-PLOTTING/ZONE SET menu: with the cursor
set the desired dimensions of the auto-lock-on zone in angle, in width (1 nautical
mile), in range (up to 20 nautical miles) and press the ENTER button. The guard
zone is effective if the zone boundaries are observed on the screen. When a target
appears in the guard zone, it is locked-on for auto-tracking, and the message TARGET
AUTO-LOCK-ON appears on the message board, accompanied by a sound signal.
Targets acquisition and display of ARP information on the screen are provided on
scales from 3 to 24 miles.
The criterion for target acquisition in the auto-lock-on zone is a target detection
in a row on three sweeps (3 out of 3) or—four detection facts on eight sweeps (4
out of 8). Thus, the delay time from the moment the target crosses the border of
auto-lock-on zone to the symbol appearance of tracking start (dotted square) will
12 Radar Systems of Maritime Transport
When yawing or changing the heading of own ship, the OK changes its position
within (345–0–15°), returning, each time by a jump to zero of azimuth scale when
reaching the extreme positions. The advantage of this mode is orientation of the radar
image in accordance with the situation observed along the course of the vessel, stabilization of the radar image in the direction. It is recommended to use the orientation
mode “Course STabilized” when following in narrow corners and along coastlines.
In the NORTH orientation mode, the north direction (OC) is always upwards at
zero mark of azimuth scale, and the heading mark (OK) indicates the direction of
the ship, i.e. the ship’s gyrocompass heading. When the course changes, the position
of the target blips on the indicator screen remains unchanged, and the OK position
changes in accordance with the current course of the vessel. BH shows the true
bearing to the target blip. The advantage of this mode is orientation and stabilization
of the radar image in the north direction in accordance with the navigation charts,
but comparison with the real picture observed along the ship’s course is difficult.
The station can display the radar image on the indicator screen in relative or true
motion modes. In the relative motion (OD/RM) mode, the sweep center is stationary,
and in the true motion (ID/TM) mode, the sweep center moves according to the
data from the stabilization sensors measuring own ship’s speed (as a vector), and
after passing through 2/3 of the screen radius, it automatically returns to the point
opposite to the direction of motion and continues to move in accordance with the
data from the stabilization sensor.
Radar plotting. Automatic radar plotting (ARP) operates only in stabilization
modes NORTH and COURSE ST from gyrocompass. To manually lock-on a target
for auto-tracking, it is necessary to place the cursor (not necessarily exactly) on the
selected target and press the LOCK-ON button. The criterion for lock-on (taking
a target for auto-tracking) is the condition of detecting the target at least twice in
three surveys, while the target will have a symbol (dotted square) starting the AC
(auto-tracking) operation.
If the lock-on has occurred, then no later than 30 s, and the target must have a
target movement and approaching vector: range, bearing, course (heading), speed,
distance of shortest approach (DSA), time of shortest approach (TSA), distance to
course intersection point (DCI), time to course intersection point (TCI).
Guard zone—the zone of targets auto-lock-on for auto-tracking (target acquisition) is activated through the AUTO-PLOTTING/ZONE SET menu: with the cursor
set the desired dimensions of the auto-lock-on zone in angle, in width (1 nautical
mile), in range (up to 20 nautical miles) and press the ENTER button. The guard
zone is effective if the zone boundaries are observed on the screen. When a target
appears in the guard zone, it is locked-on for auto-tracking, and the message TARGET
AUTO-LOCK-ON appears on the message board, accompanied by a sound signal.
Targets acquisition and display of ARP information on the screen are provided on
scales from 3 to 24 miles.
The criterion for target acquisition in the auto-lock-on zone is a target detection
in a row on three sweeps (3 out of 3) or—four detection facts on eight sweeps (4
out of 8). Thus, the delay time from the moment the target crosses the border of
auto-lock-on zone to the symbol appearance of tracking start (dotted square) will