Furuno FR-2105-B - Manual (Page 105)

- 2 . 26-
Target Course Speed CPA TCPA
(kt) (nm) (min)
Target A 90.0°T 10.0 1.0 10.4
Target B 0.0°T 0.0 4.0 -
Target C 180.0°T 10.0 1.7 28.2
Target D 216.5°T 23.8 0.9 15.0
Target E 273.5°T 14.2 6.0 22.5
Target F 180.0°T 20.0 0.0 30.0
Target G 24.6°T 15.6 4.0 43.6
000 010
020
030
040
050
060
070
080
090
220
240
250
100
110
120
130
140
150
160
170 180 190
200
210
230
260
270
280
290
300
310
320
330
340
350
F
C
B
A
G
E
D
XX
Note: Note that target numbers are subject to change. If test results show any deviation from
the above, consult with your service representative.
2.18 Criteria for Selecting Targets for Tracking
The FURUNO ARPA video processor detects targets in midst of noise and discriminates radar
echoes on the basis of their size. Target whose echo measurements are greater than those of
the largest ship in range or tangential extent are usually land and are displayed only as normal
radar video. All smaller ship-sized echoes which are less than this dimension are further
analyzed and regarded as ships and displayed as small circles superimposed over the video
echo.
When a target is first displayed, it is shown as having zero true speed but develops a course
vector as more information is collected. In accordance with the International Marine
Organization Automatic Radar Plotting Aid (IMO ARPA) requirements, an indication of the
motion trend should be available within 20 scans of antenna and full vector accuracy within
60 scans. The FURUNO ARPAs comply with these requirements.
Acquisition and tracking
A target which is hit by 5 consecutive radar pulses is detected as a radar echo. Manual
acquisition is done by designating a detected echo with the trackball. Automatic acquisition is
done in the acquisition areas when a target is detected 5-7 times continuously depending upon
the congestion. Tracking is achieved when the target is clearly distinguishable on the display
for 5 out of 10 consecutive scans whether acquired automatically or manually. Required
tracking facilities are available within 0.1-32 nm on range scales including 3, 6, 12 nm, full
plotting information is available within one scan when the range scale has been changed.
Targets not detected in 5 consecutive scans become "lost targets."
Quantization
The entire picture is converted to a digital from called "Quantified Video." A sweep range is
divided into small segments and each range element is "1" if there is radar echo return above a
threshold level, or "0" if there is no return.