Radar & ARPA

Question 1

How would you set up a radar?

Answer 1

Big Randy Girls Take Cock

Check up the mast, open permit to work turn on and warm up

B - Brilliance

R - Range

G - Gain

T - Tune

C - Clutter (Sea & Rain)

Question 2

What determines a good radar conspicuous object?

Answer 2

MASTS

M - Material

A - Aspect

S - Size

T - Texture

S - Shape

Question 3

Under Solas Chapter V, what navigation equipment must all vessels have on board?

Answer 3

• Magnetic compass
• Pelorus
• Means of correcting heading and bearings to true at all times
• Nautical charts and publications sufficient for the intended voyage
• ECDIS with suitable backup arrangements
• GNSS receiver
• Means of communication to the emergency steering position
• Sound reception devices for totally enclosed bridge wings

Question 4

What should all ships that are over 150 GT and all passenger ships carry as extra navigation equipment?

Answer 4

• Spare magnetic compass
• Daylight signalling lamp (Aldis lamp)
• Bridge navigational watch alarm system (BNWAS)

Question 5

What should all ships that are over 300 GT and all passenger ships carry as extra navigation equipment?

Answer 5

• Echo sounding device
• 9Ghz radar and electronic plotting aid
• Speed log capable of measuring speed through the water
• Adjusted heading transmitting device
• Automatic identification system (AIS)

Question 6

What should all ships that are over 500 GT and all passenger ships carry as extra navigation equipment?

Answer 6

• Gyro-compass and heading repeater and bearing device
• Rudder, propeller, thrust, pitch and operational mode indicators

Question 7

What should all ships that are over 3000 GT and all passenger ships carry as extra nav equipment?

Answer 7

3GHz radar and ATA

Question 8

How does radar work?

Answer 8

1. Radar sends out a PULSE through the transmitter at the speed of light
2. Pulse attenuates as it moves through space
3. Pulse strikes a TARGET
4. ECHO returns to receiver
5. Echo is received by ANTENNA
6. Contact appears on radar DISPLAY
7. Range is (speed x time/2)

Question 9

What is meant by pulse length?

Answer 9

Short pulse length - travel shorter distance but are more precise

Long pulse length - travel further but are less precise

Question 10

What is X band radar?

Answer 10

• 3cm beam width at 10GHz
• Most effective at close ranges
• Effected by rain and sea
• High definition due to narrower beam width
• Can detect SARTs

Question 11

What is S band radar?

Answer 11

• 10cm beam width at 3GHz
• Most effective at long range
• Better rain penetration
• Less definitive due to wider beam
• 3x wider antenna requires same definition

Question 12

What is the relationship between frequency and wave length?

Answer 12

The higher the frequency, the shorter the wavelength, and the lower the frequency, the longer the wavelength. The energy of a wave is directly proportional to its frequency but inversely proportional to its wavelength.

Question 13

What are the errors of radar?

Answer 13

• Side lobe effect
• Shadow & blind sectors
• Spurious echoes and effects
• Indirect echoes
• Multiple echoes
• Radar interference
• Radar horizon

Question 14

What is bearing discrimination?

Answer 14

The ability of the radar to detect targets at the same range but on different bearings

Question 15

What is range discrimination?

Answer 15

The ability of the radar to detect targets on the same bearing but at different ranges

Question 16

What is side lobes?

Answer 16

Leaking energy from the side of the main lobe pulse

Question 17

What is multiple echoes?

Answer 17

When the echo bounces off target and then back off own ship to target multiple times

Question 18

What are indirect (false) echoes?

Answer 18

When the echos bounce off something on own vessel and return a false target position

Question 19

What is the difference between blind and shadow sectors?

Answer 19

Blind sectors are areas where the radar transmissions are totally obscured and no echoes will be found

Shadow sectors are areas partially obscured and only faint echoes if any will be found

Question 20

What is a sea stabilised radar?

Answer 20

• Speed and heading from gyro and log
• Course and speed through the water
• Used for collision avoidance
• True aspect of vessel easily determined

Question 21

What is a ground stabilised radar?

Answer 21

• Speed and heading from GNSS
• Course and speed over the ground
• Used for coastal navigation
• Difficult to determine true aspect of vessel
• A fixed target will appear stationary

Question 22

What are the pre-departure radar checks?

Answer 22

• The performance of the radar should be checked using the performance monitor before sailing and at least every four hours while a radar watch is being maintained.
• VRM checks against range rings
• ERBL cross check against compass

Question 23

What is good radar practice / limitations of the radar?

Answer 23

• Performance monitoring
• Misalignment of the heading marker
• Small vessels not detected by the radar
• Video processing techniques should be used with care
• Echoes may be obscured by sea or rain clutter
• Shadow or blind sectors

Question 24

What is the performance monitor?

Answer 24

Provides a check of the performance of the transmitter.

Question 25

What is the difference between a stabilised and an un-stabilised radar display?

Answer 25

- Stabilised means the orientation of the display is fixed to an unchanging reference (North up + Course up) - Un-stabilised means the orientation changes with changes in own ship’s heading (Head up)

Question 26

What is meant by a head up display?

Answer 26

Un-stabilised by any external heading input, heading line is always directly upwards on display so bearings will be relative to ships head.

Question 27

What is meant by course up display?

Answer 27

Stabilised by external heading input, small alterations of headings are shown by the heading marker swinging from side to side. Bearings can be taken relative or true.

Question 28

What is meant by North up display?

Answer 28

Image is stabilised and it aligns with a chart or chart plotter. This is the standard setting.

Question 29

What is ARPA?

Answer 29

Automatic Radar Plotting Aid - Automated aid of radar plotting the WOA triangle - Target is acquired manually or automatically in guard zone - Target goes into the box acquisition phase - After 3 minutes the ARPA will be steady tracking the target

Question 30

What is target swap error in ARPA?

Answer 30

Two targets come close together and the ARPA can swap the target and only track one of them. Deselect both targets and re-acquire them.

Question 31

What are radar plotting aids?

Answer 31

- Smaller ships may be fitted with Automatic Tracking Aid (ATA) or Electronic Plotting Aid (EPA) - ARPA required on vessels of 10000 GT and above - They provide an automatic tool for the systematic plotting of detected objects as required by the COLREGS - Correct and reliable speed and heading inputs into ARPA are essential if information is to be processed correctly

Question 32

What else are Radar / ARPA systems able to display?

Answer 32

AIS target information if connected to the AIS transponder. The ARPA should clearly indicate whether target information comes from ARPA or AIS.

Question 33

What size vessels must show ARPA?

Answer 33

10000 GT and above

Question 34

What is the difference between true and relative motion?

Answer 34

Relative motion - the motion of a target relative to the motion of the observing ship True Motion - the actual or true motions of the target and the observing ship.

Question 35

How would you set a radar up for the best results to detect a SART?

Answer 35

- Detune the radar - Set radar range scale to 6 or 12 miles - Sea clutter set to a minimum - Set rain clutter to match conditions

Question 36

When did they take differential GPS, the main form of GBAS out of operation in the UK?

Answer 36

2022