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RADAR FUNDAMENTALS
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Compiled by 3/O Moises T. Teñosa
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COURSE OBJECTIVES CONTENTS SUMMARY
• 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.
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
NEXTRETURN
RADAR
How
does
RADAR
work?
Components of a radar system
INDICATOR-OR PPI
TRANSMITTERMODULATOR
ANTENNA
CREATES HIGH ENERGYRADIO FREQUENCY
WAVES
TURNS RADIOFREQUENCIES
ON AND OFF
RECEIVER
TRANSMIT
RECEIVE
ROTATINGANTENNA
CRT
LCD
ColorBlack Box
Pulse Length
Receiver Sensitivity
Frequency
Power Output
Horizontal Beam Width
THETHE
PPLANLAN
PPOSITIONOSITION
IINDICATORNDICATOROROR PPI PPI
wide beam widthwide beam width
RADARRADARBeam width is moreBeam width is more important than powerimportant than power
THETHE
PPLANLAN
PPOSITIONOSITION
IINDICATORNDICATOROROR PPI PPI
RADARRADARBeam width is moreBeam width is more important than powerimportant than power
narrow beam widthnarrow beam width
large antenna
narrow beam width
small antennawide beam width
Maximum Radar Range
D = 1.22 H
D = 1.22 X 5.48 = 6.68 nm
where radar is 30 feet above the water
It can display the locationof certain fixed and moving objects in relation to your vessel
Radar --is not electronic NavigationRadar cannot tell you where you
are
Radar -- is electronic plotting
anim
atio
n
but
RADAR generates
a
relative motion
picture
Geographic Plot shown on Maneuvering Board
Radar Plot
23002200Relative Motion
Radar Plot
Geographic Plot shown on Maneuvering Board FormRadar Plot
anim
atio
n
anim
atio
n
ThePlan
PositionIndicator
Or PPI
A target whose rangeis decreasing andrelative bearing isnot changing is on acollision course
Make a RADICAL
Course Change
in order for it
TO BE OBVIOUS
on Radar
CPA
Closest Point of Approach
CPA
RADAR PLOTTING ANDRELATIVE MOTION
VESSEL IS STEAMING ONA COURSE
OF280 T AT 9 KNOTS
THE PPI SHOWS TARGETS
at 1305 323 R 9.0 nmat 1313 324 R 6.5 nmat 1320 327 R 4.4 nmat 1325 331 R 3.0 nm
RADAR PLOTTING ANDRELATIVE MOTION
HOW CLOSE WILL THIS TARGET COME
TO OUR VESSEL, AND AT WHATTIME WILL IT APPROACH
CLOSEST TO OUR VESSEL
RADAR PLOTTING ANDRELATIVE MOTION
1305130513131313
1320132013251325
CONVERT RELATIVEBEARINGS TO
TRUE BEARINGS
322 + 280 = 242324 + 280 = 244327 + 280 = 247334 + 280 = 251
PLOT ON MANEUVERING BOARD
LABEL EACH WITH TIME OBSERVED
RADAR PLOTTING ANDRELATIVE MOTION
13051313
13201325
DIRECTION O
F RELATIVE MOTIO
N =>
DRAW A LINE THROUGH
ALL 4 POINTS
RADAR PLOTTING ANDRELATIVE MOTION
13051313
13201325
DIRECTION O
F RELATIVE MOTIO
N =>
D = 6.1
RELATIVE SPEED OF TARGETT = 1325 - 1305
T = 0020
S = 60 X D T
S = 60 X 6.1 20
S = 18.3 kts
RELATIVE SPEED =18.3 kts
RADAR PLOTTING ANDRELATIVE MOTION
13051313
13201325
DIRECTION O
F RELATIVE MOTIO
N =>
RELATIVE COURSE = 058
RELATIVE COURSE = 058
RADAR PLOTTING ANDRELATIVE MOTION
13051313
13201325
DIRECTION O
F RELATIVE MOTIO
N =>
YOUR SHIP ISAT THE CENTER
CLOSEST POINT OF APPROACH
IS FROM THE CENTER
OFMANEUVERING BOARD
TO THE LINE
OF RELATIVE MOTION
(AT RIGHT ANGLES)
058 - 90 = 328
RADAR PILOTING ANDRELATIVE MOTION
13051313
13201325
DIRECTION O
F RELATIVE MOTIO
N =>MEASURE CPA
DISTANCE
CPA DISTANCE
IS
0.7 nm
at 1328
RADAR PLOTTING ANDRELATIVE MOTION
13051313
13201325
DIRECTION O
F RELATIVE MOTIO
N =>
T = 60 D ST = 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 POINTTO CPA IS 9 nm.
RADAR PLOTTING ANDRELATIVE MOTION
1305130513131313
1320132013251325
DIRECTION O
F RELATIVE MOTIO
N =>
DIRECTION O
F RELATIVE MOTIO
N =>
THE RADAR TARGET
WILL APPROACH
CLOSEST
TO THE SHIP AT 1335
THE CLOSEST IT WILL COME
WILL BE 0.7 nm
RADAR PLOTTING ANDRELATIVE MOTION
WHAT IS THE SPEED
AND DIRECTION
OF THE
TARGET?
RADAR PLOTTING ANDRELATIVE MOTION
C280S9
THIS IS NOW A VELOCITY
PLOT ON THE MANEUVERING
BOARD
PLOT YOUR VESSEL’S
VELOCITY VECTOR
OWN CRSAND SPD
RADAR PLOTTING ANDRELATIVE MOTION
C280S9
PLOT
RELATIVE VELOCITY
VECTOR OF TARGET
058
at 18.3 kts
REL CRS 058REL VEL 18.3
RADAR PLOTTING ANDRELATIVE MOTION
C280S9
DRAW VECTOR
FROM
CENTER
TO
HEAD OF RELATIVE
VELOCITY VECTOR
OF
TARGET
RADAR PILOTING ANDRELATIVE MOTION
C280S9
THIS IS
THE TARGET’S
TRUE COURSE
030
AND ITS
TRUE SPEED
13 kts
WHAT REALLY HAPPENED IN REAL TIME ON THE WATER
WHAT REALLYHAPPENED
OWN SHIP
POSITION
AT 1305 HOURS
TARGET IS 242 T
AT 9 MILES
Target Positionat 1305
242 T 9 nm
Own SHIP Positionat 1305
WHAT REALLYHAPPENED
OUR SHIP
POSITION
AT 1313
TARGET IS 244 T
AT 6.5 nm
Target Positionat 1313
Advance own SHIP fromthe 1305 position to
the 1313 position
1305
1313 - 1305 = 860 D = S x T
D = S x T / 60D = 9 x 8 / 60D = 1.2 nm
244 T 6.5 nm
242 T 9 nm
1313
1305
WHAT REALLYHAPPENED
Advance own ship fromthe 1305 position to
the 1320 position
1320
OUR SHIP
POSITION
AT 1320
TARGET IS 247 T
AT 4.4 nm
1320 - 1305 = 1560 D = S x T
D = S x T / 60D = 9 x 15 / 60D = 2.25 nm
247 T 4.4 nm
244 T 6 nm
242 T 9 nm
WHAT REALLYHAPPENED
Advance own ship fromthe 1305 position to
the 1325 position
1325
OUR SHIP
POSITION
AT 1325
TARGET IS 251 T
AT 3 nm
1325 - 1305 = 2060 D = S x T
D = S x T / 60D = 9 x 20 / 60
D = 3 nm
244 T 6 nm
242 T 9 nm
247 T 4.4 nm251 T 3 nm
1305
WHAT REALLYHAPPENED
TARGET SHIPDIRECTION IS
030 TRUE
1325OWN SHIP
WILL THE TWO SHIPSCOLLIDE?
TARGETSHIPSHIP
242 T 9 nm
244 T 6 nm
247 T 4.4 nm
251 T 3 nm1305
WHAT REALLYHAPPENED
CALCULATEDCLOSEST POINTOF APPROACH
OCCURS AT1335
TARGETSHIPSHIP
242 T 9 nm
251 T 3 nm
OWN SHIPT1325
1305TARGET SHIP
COURSEDIRECTION IS
030 TRUE
WILL THE TWO SHIPSCOLLIDE?
WHAT REALLYHAPPENED
TARGETSHIPSHIP
1305
1335OWN SHIP
242 T 9 nm
251 T 3 nm
WILL THE TWO SHIPSCOLLIDE?
AT 1335
OWN SHIP POSITIONIS:
1335 - 1305 = 30
D = S X T / 60
D = 9 X 30 / 60
D = 4.5
WHAT REALLYHAPPENED
242 T 9 nm
251 T 3 nm
1335
TARGETSHIPSHIP
OWN SHIPSHIP
1335
1305
WILL THE TWO SHIPSCOLLIDE?
AT 1335
TARGETSHIP POSITION
IS:
1335 - 1305 = 30
D = S X T / 60
D = 13 X 30 / 60
D = 4.5
ADVANCE THE TARGET SHIPFROM 1305 TO 1335 POSITION
.7 MILES.7 MILES
WHAT REALLYHAPPENED
WILL THE TWO
SHIPSCOLLIDE?
OWNSHIPSHIP
1335
1305
TARGETSHIPSHIP
MEASURE THEDISTANCE BETWEEN THE
BLUE AND ORANGEDOTS
1335
0.7 MILES0.7 MILES
NO!
RADAR PLOTTING ANDRELATIVE MOTION
1305
328
OWN SHIPSHIP
TARGETSHIPSHIP
0.7 MILES 0.7 MILES
328 DEGREES TRUE TO
THE CLOSEST POINT
OFAPPROACH
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
Range
Bearing
Entering Harbor
RACON
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.
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.
Re-Usable Maneuvering Board
RETURN
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.
• 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.
• RANGE is the distance from the radar site to the target measured along the line of sight. The concepts are illustrated in the figure.
• 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.
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