4. • On completion of the subject, the students
should be able to plot positions by means of
radar, making them capable of navigating
safely in all parts of the world. They will have
specific knowledge the operating principles,
limitations, sources of error and methods of
correction to radar to obtain accurate position
fixing. They will have enough skills in radar
plotting for collision avoidance.
5. CONTENTS
• 1. Fundamental of Radar
• 2. Radar Components and System
• 3. Radar Motion Display
• 4. Radar Controls
• 5. Introduction to Radar Plotting and
Tracking Problems
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9. Components of a radar system
INDICATOR-
OR PPI
TRANSMITTERMODULATOR
ANTENNA
CREATES HIGH ENERGY
RADIO FREQUENCY
WAVES
TURNS RADIO
FREQUENCIES
ON AND OFF
RECEIVER
TRANSMIT
RECEIVE
ROTATING
ANTENNA
18. Maximum Radar Range
D = 1.22 H
D = 1.22 X 5.48 = 6.68 nm
where radar is 30 feet above the water
19.
20. It can display the location
of certain fixed and moving
objects in relation to your vessel
Radar --
is not electronic Navigation
Radar cannot tell you where you are
Radar -- is electronic plotting
30. RADAR PLOTTING AND
RELATIVE MOTION
VESSEL IS STEAMING ON
A COURSE
OF
280 T AT 9 KNOTS
THE PPI SHOWS TARGETS
at 1305 323 R 9.0 nm
at 1313 324 R 6.5 nm
at 1320 327 R 4.4 nm
at 1325 331 R 3.0 nm
31. RADAR PLOTTING AND
RELATIVE MOTION
HOW CLOSE WILL
THIS TARGET COME
TO OUR VESSEL,
AND AT WHAT
TIME WILL IT
APPROACH
CLOSEST TO OUR
VESSEL
32. RADAR PLOTTING AND
RELATIVE MOTION
13051305
13131313
13201320
13251325
CONVERT RELATIVE
BEARINGS TO
TRUE BEARINGS
322 + 280 = 242
324 + 280 = 244
327 + 280 = 247
334 + 280 = 251
PLOT ON
MANEUVERING BOARD
LABEL EACH
WITH TIME OBSERVED
33. RADAR PLOTTING AND
RELATIVE MOTION
1305
1313
1320
1325
DIRECTION
OF RELATIVE
MOTION
=>
DRAW A LINE
THROUGH
ALL 4 POINTS
34. RADAR PLOTTING AND
RELATIVE MOTION
1305
1313
1320
1325
DIRECTION
OF RELATIVE
MOTION
=>
D = 6.1
RELATIVE SPEED
OF TARGET
T = 1325 - 1305
T = 0020
S = 60 X D
T
S = 60 X 6.1
20
S = 18.3 kts
RELATIVE SPEED =18.3 kts
35. RADAR PLOTTING AND
RELATIVE MOTION
1305
1313
1320
1325
DIRECTION
OF RELATIVE
MOTION
=>
RELATIVE COURSE = 058
RELATIVE
COURSE = 058
36. RADAR PLOTTING AND
RELATIVE MOTION
1305
1313
1320
1325
DIRECTION
OF RELATIVE
MOTION
=>
YOUR SHIP IS
AT THE CENTER
CLOSEST POINT
OF APPROACH
IS
FROM THE CENTER
OF
MANEUVERING BOARD
TO
THE LINE
OF
RELATIVE MOTION
(AT RIGHT ANGLES)
058 - 90 = 328
37. RADAR PILOTING AND
RELATIVE MOTION
1305
1313
1320
1325
DIRECTION
OF RELATIVE
MOTION
=>
MEASURE CPA
DISTANCE
CPA
DISTANCE
IS
0.7 nm
at 1328
38. RADAR PLOTTING AND
RELATIVE MOTION
1305
1313
1320
1325
DIRECTION
OF RELATIVE
MOTION
=>
T = 60 D
S
T = 60 X 9 = 30 MIN
18.3
MEASURE DISTANCE FROM
1305 POINT TO CPA POINT
COMPUTE TIME
TO TRAVERSE
FROM
1305 PT TO CPA
ADD TIME TO 1305
1305 + 0030 = 1335
CPA OCCURS AT 1335
COMPUTE TIME TO CPA
DISTANCE FROM 1305 POINT
TO CPA IS 9 nm.
39. RADAR PLOTTING AND
RELATIVE MOTION
13051305
13131313
13201320
13251325
DIRECTION
OF RELATIVE
MOTION
=>
DIRECTION
OF RELATIVE
MOTION
=>
THE RADAR TARGET
WILL APPROACH
CLOSEST
TO THE SHIP
AT 1335
THE CLOSEST
IT WILL COME
WILL BE 0.7 nm
47. WHAT REALLY
HAPPENED
OUR SHIP
POSITION
AT 1313
TARGET IS 244 T
AT 6.5 nm
Target Position
at 1313
Advance own SHIP from
the 1305 position to
the 1313 position
1305
1313 - 1305 = 8
60 D = S x T
D = S x T / 60
D = 9 x 8 / 60
D = 1.2 nm
244 T 6.5 nm
242 T 9 nm
1313
48. 1305
WHAT REALLY
HAPPENED
Advance own ship from
the 1305 position to
the 1320 position
1320
OUR SHIP
POSITION
AT 1320
TARGET IS 247 T
AT 4.4 nm
1320 - 1305 = 15
60 D = S x T
D = S x T / 60
D = 9 x 15 / 60
D = 2.25 nm
247 T 4.4 nm
244 T 6 nm
242 T 9 nm
49. WHAT REALLY
HAPPENED
Advance own ship from
the 1305 position to
the 1325 position
1325
OUR SHIP
POSITION
AT 1325
TARGET IS 251 T
AT 3 nm
1325 - 1305 = 20
60 D = S x T
D = S x T / 60
D = 9 x 20 / 60
D = 3 nm
244 T 6 nm
242 T 9 nm
247 T 4.4 nm
251 T 3 nm
1305
51. WHAT REALLY
HAPPENED
CALCULATED
CLOSEST POINT
OF APPROACH
OCCURS AT
1335
TARGET
SHIPSHIP
242 T 9 nm
251 T 3 nm
OWN SHIPT
1325
1305
TARGET SHIP
COURSE
DIRECTION IS
030 TRUE
WILL THE
TWO SHIPS
COLLIDE?
53. WHAT REALLY
HAPPENED
242 T 9 nm
251 T 3 nm
1335
TARGET
SHIPSHIP
OWN
SHIPSHIP
1335
1305
WILL THE
TWO SHIPS
COLLIDE?
AT 1335
TARGET
SHIP POSITION
IS:
1335 - 1305 = 30
D = S X T / 60
D = 13 X 30 / 60
D = 4.5
ADVANCE THE TARGET SHIP
FROM 1305 TO 1335 POSITION
54. .7 MILES.7 MILES
WHAT REALLY
HAPPENED
WILL
THE
TWO
SHIPS
COLLIDE?
OWN
SHIPSHIP
1335
1305
TARGET
SHIPSHIP
MEASURE THE
DISTANCE BETWEEN THE
BLUE AND ORANGE
DOTS
1335
0.7 MILES0.7 MILES
NO!
55. RADAR PLOTTING AND
RELATIVE MOTION
1305
328
OWN
SHIPSHIP
TARGET
SHIPSHIP
0.7 MILES 0.7 MILES
328 DEGREES TRUE
TO
THE
CLOSEST POINT
OF
APPROACH
56.
57. Order of preference for accuracy
To determine position
•Visual observation of object’s
relative bearing and distance
Determined by radar
•Radar range to two objects
•Radar range and radar relative
bearing on same object
•Radar relative bearings to two
Different objects
62. Steering and Sailing Rules
Rule 7
Risk of Collision
(a) Every vessel shall use all available means appropriate to the
prevailing circumstances and conditions to determine if risk of
collision exists. If there is any doubt such risk shall be deemed to
exist.
(b) Proper use shall be made of radar equipment if fitted and
operational, including long-range scanning to obtain early
warning of risk of collision and radar plotting or equivalent
systematic observation of detected signals.
(c) Assumptions shall not be made on the basis of scanty
information, especially scanty radar information.
63. Steering and Sailing Rules
Rule 7
Risk of Collision (continued)
(d) In determining if risk of collision exists the following
considerations shall be among those taken into account.
(I) such risk shall be deemed to exist if the compass
bearing of an approaching vessel does not appreciably change;
(ii) such risk may sometimes exist even when an
appreciable bearing change is evident, particularly when
approaching a very large vessel or a tow or when approaching a
vessel at close range.
68. The following paragraphs summarize the
important points of this chapter.
• RADAR is an electronic system that uses
reflected electromagnetic energy to detect
the presence and position of objects invisible
to the eye.
• TARGET POSITION is defined in
reference to true north, the horizontal
plane, and the vertical plane.
69. • TRUE BEARING is the angle between true
north and the line of sight to the target,
measured in a clockwise direction in the
horizontal plane.
• ELEVATION ANGLE is the angle between
the horizontal plane and the line of sight,
measured in the vertical plane.
70. • RANGE is the distance from the radar site
to the target measured along the line of
sight. The concepts are illustrated in the
figure.
71.
72. • BEARING RESOLUTION is the ability of a
radar to separate targets at the same range
but different bearings. The degree of bearing
resolution is dependent on beam width and
range. The accuracy of radar is largely
dependent on resolution.
Furuno’s new “black box” radar with flat screen computer monitor display, $15,000.
Uses personal computer to process radar signals and then display them on any computer monitor.
Shorter pulse length permits detection of closer in targets - some radar units change pulse length as range selection is decreased, this is an important feature
Power output determines range capability to some degree, also ability to “see through” fog and rain - minimum 4 KW recommended for fog and rain
Horizontal beam width determines ability to discriminate between targets close together and provides more accurate bearings - the narrower the beam the better
Receiver sensitivity determines ability to “see” targets - the higher the sensitivity the better
Open array radar antenna provides narrow radar beam width - the larger the antenna, the narrower the radar beam width
Radomes provide smaller size, lighter weight, and less windage than open arrays. Provide protection of the rotating element within from the elements - wider beam width than open arrays
Radar range is generally limited by the curvature of the earth - Radar beam distance to the horizon is equal to the square root of the height of the antenna times the constant, 1.22
In the example given the antenna height is 36 feet, the square root of which is 6 - the radar range to a short target is therefore only about 7 miles - the taller the target, the farther the distance at which it can be “seen”
This demonstrates how own vessel and target vessel actually move over time - movement is plotted on a maneuvering board display for convenience and comparison purposes
This demonstrates how own vessel and target vessel actually move over time - movement is plotted on a maneuvering board display - relative motion actual radar plot is shown in red compared to actual geographic movement of vessels
This animated slide combines both the actual motion and the relative motion plots of a target on the radar screen.
A TARGET WHOSE RANGE
IS DECREASING AND
RELATIVE BEARING IS
NOT CHANGING IS ON A
COLLISION COURSE
Closest point of approach (CPA) is the shortest distance between vessels that will occur provide both vessels maintain course and speed
A typical LCD radar display set on one mile range (R 1) showing 0.25 mile range rings ( RR .25)and two electron bearing lines (EBL) and two variable range markers (VRM)plus a GPS on-screen lat/lon input
Land on the left and on the right. Buoy line indicating the harbor channel is visible on the radar. Most major harbor buoys are equipped with radar reflectors making them good radar targets.
A racon is a radar beacon which produces a coded response in the form of a morse code character on the radar screen, when triggered by a radar signal. Racons are becoming more prevalent as an aid to navigation to mark bridges or superstructures that present a significant hazard to navigation. Racons provide radar enhancement, improve aid identification, and help during the transition from ocean to inland navigation. A racon on an aid to navigation assists the mariner in distinguishing that aid from other aids and vessels.
Order from:
http://WWW.oceannavigator.com/cur/store/#
$20.00
Left side: Firdell Blipper Radar reflector
Lower right - typical corner reflectors - use in the “catch rain” position for maximum effectiveness
Upper right - Collision Avoidance Radar Detector - listens for and reports the presence of other vessels radar beams