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NAV&RADAR MCA > MOCK Exams > Flashcards

MOCK Exams Flashcards

1
Q

MOCK 1 Answers (Part B)

A
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2
Q

RADAR

A
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3
Q

(a) Describe the foundation principle of how a range of a detected target is calculated by radar (2)

A
  1. Radar send PULSE by the Transmitter at the speed of light (300,000,000 m/s)
  2. Pulse attenuates as it moves trough space
  3. Pulse strikes a TARGET
  4. ECHO return to receiver
  5. Echo is received by ANTENNA
  6. Contact is seen on a radar DISPLAY
  7. Range is speed X time divided 2
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4
Q

(b) List the factors that affect the detectability of a radar target (5)

A
  • Material - Steal work better then other
  • Aspect - Only perpedicular surface surface will return Echos
  • Size - Bigger is the target better change you have a return of
  • Texture - Ruff surface will have more likelihood to be hidden by a echo
  • Shape - Cubes are better than spheres when perpendicular to the scanner
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5
Q

(c) Describe the meaning of Range discrimination of a Radar (5)

A

Is the ability of the radar to detect target on different ranges but on the same bearing

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6
Q

(d) Describe the meaning of Bearing discrimination of a Radar (5)

A

Is the ability of the radar to detect target on different ranges but on the same bering

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7
Q

(e) Describe the cause and effect of blind and shadow sectors of a Radar (3)

A
  • Blind sectors are areas where the radar transmissions are completely obscured and no echoes will be found.
  • Shadow sectors are areas of reduced sensitivity where radar may pick up some targets.
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8
Q

COMPASS

A
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9
Q

(a) Define magnetic variation of a compass (2)

A

Is the angular difference between Magnetic nord and True Nord

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10
Q

(b) What are the two types of deviation of a magnetic compass and what are their causes? (5)

A

Permanent deviation

  • Is the entire influence on the compass from all the combined part of your vessel sach us: Engine, Generators, Ancor, Hull, Ecc.

induced deviation

  • Build of a charge from the heart magnetic field accumulating in any ferrous material of the vessel
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11
Q

(c) What are the correctors used on a marine magnetic compass to reduce magnetic deviation? (3)

A

Permanent Deviation

  • Addition of longitudinal and transversal correcting magnets

Induced Deviation

  • On marine compasses is corrected using soft Iron Kelvins Balls and Flinders.
  • If the vessel has an aft bridge the bar need to be fit forward and for a forward bridge the bar would be fitted aft
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12
Q

(d) Explain why deviation changes with the ships head (3)

A
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13
Q

(e) How often should the OOW check the compass error? (2)

A
  • Pre-deperture
  • Once a watch
  • After every large alteration of course
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14
Q

(f) How would you carry out a compass check onboard? (5)

A

Transit

In pre-departure, If you’re Square dock along side compare our heading to the alignment to the dock

Charted known bearing

Sun azimut

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15
Q

GPS

A
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16
Q

(a) What are the three segments of the GPS system? (3)

A
  • Space Segment - 24 satellite 6 orbit
  • Ground Segment - 1 master (Colorato USA) 5 monitoring station near Equator
  • User Segment - Any GPS receiver
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17
Q

(b) Explain how a position is calculated using the GPS system (5)

A
  • Satellite transmit signal with Time and Position
  • Receiver receive the signal
  • Receiver know the start time
  • Receiver workout the time difference and calculate the range from the satellite
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18
Q

(c) Explain the term HDOP and when/where it might occur (5)

A
  • Dilution of precision: The reliability of the data due to the geometry (azimut and elevation) of satellites in view of the receiver.
  • Horizontal DOP -
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19
Q

(d) What is the datum used with GPS? (1)

A

WGS 84 - Is the reference where the position is calculated from

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20
Q

(e) Can you use a chart that references a different datum to that of the one being used on the GPS? (2)

A

Yes, if I have acces to the difference between the two datum

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21
Q

(t) List the possible errors of the GPS (4)

A
  • Satellite time error
  • Satellite Orbit error
  • Ionosphere Delay Error
  • Troposphere Delay Error
  • User Timer Error
  • User Noise Error
  • Multi-Path Error
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22
Q

MOCK 4 Answers (Part B)

A
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23
Q

ARPA

A
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24
Q

A) What does ARPA stand for? (2)

A

Automatic Radar Plotting Aid

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25
Q

B) Describe how the ARPA work (5)

A
  • Arpa is an automated aid of Radar plotting OAW.
  • The target is acquired (Manually or Automatic or in Guard Zone)
  • The target goes in the Box acquisition phase. ARPA return range and bearing
  • After 3 minute the ARPA will steady tracking the target.
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26
Q

C) What information does ARPA Provide to the Watch-keeper

A

Range and bearing

CPA & TCPA

Calculate Course and Speed

Bow Crossing Time Bow crossing distance

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27
Q

D) What effect would a faulty heading and/or speed input have on the information read out from the ARPA (6)

A

It would return a faulty reading on the OWA

W-O and W-A would be a false reading from the Gyro

W-O only would be a false reading from the Log

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28
Q

E) Can ARPA be used for IRCPS? (2)

A

Yes, as long we are verifying the information are correct with other means.

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29
Q

PARRALEL INDEX

A
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30
Q

a) Describe the term “Parrallel Indexing) (3)

A

Tool to maintain cross track, error useful in Restricted Visibility and Narrow channel

31
Q

b) With the aid of a diagram show how P.I. lines are used (5)

A
32
Q

c) List some Objects which would be suitable and not be suitable to reference with P.I. (4)

A

Good

  • Land (cliff)
  • Brake water
  • Radar Conspicuis point

Bad

  • Drying height
  • Buoys
  • Moving object
  • Boats
33
Q

d) Describe Radar setup you would use for navigation with P.I. Lines (4)

A
  • North Up
  • Relative Motion
34
Q

e) Describe the use of Radar overlay and when it may be used (4)

A
  • Radar can be set over ECDIS
  • We can see GPS error where the overlay of radar does not match the feature on ECDIS
35
Q

LORAN

A
36
Q

a) What frequency does the LORAN system operate on? (2)

A

100 kHz, low radio frequency radio.

37
Q

b) Briefly describe how a position is calculated using the LORAN system (5)

A
  • Use time differences between 2 different pulses from 2 different station to get one line of position
  • Then use the time difference of another 2 station sending 2 different pulse and get another line of position.
  • With two line of position you can fix a position
  • From the center of the towers and close to those, you have a better angle of cut and a more precise position fixing
38
Q

c) What is the approximative range of LORAN for both, ground and sky wave (2)

A
  • Ground Wave - 600 to 800 NM (Depend on atmospheric condition)
  • Sky Wave - 1200 to 2000 NM (Depend on ionization)
39
Q

d) What are the Errors of the LORAN System (4)

A

2 Fix:

  • Land Error - Land slows the propagation of the pulse
  • Dimond Error or Base line extension - the area where the hyperbolic curve are more bended

2 Dynamic:

  • Clock error
  • Sky wave rejection from the Ionosphere.
40
Q

e) What is ELORAN (2)

A
  • Enhanced LORAN.
  • Use modern technology to increase accuracy of the system, correcting for known errors
41
Q

f) What are the advantages and disadvantages of LORAN against GPS? (5)

A

Pros

  • Doesn’t rely on satellite
  • Land Based
  • Can be done in Local area (Don’t need to be Global)
  • A good backup to GPS
  • Don’t have to rely to Sextant

Cons

  • Not always accurate
  • High maintenance cost
  • No world wide coverage
  • Largely discontinued
42
Q

MOCK 5 Answers (Part B)

A
43
Q

GPS

A
44
Q

A) How many satellite are require to gain a position from the GPS System

A
  • 3 satellite for a 2D positon
  • 4 satellite for a 3D position
45
Q

B) How many satellites are there in the ‘space segment’ of the GPS system?

A

24 Satellite. 4 satellite in 6 orbits planes

46
Q

C) What does DGPS means

A

Differential GPS - It use difference in position from known object to minimise errors

47
Q

D) Explain how DGPS works

A
  • DGPS use the differential in position from station known position and the GPS position reading
  • Calculate the range from the two
  • GBAS will transmit a GPS pulse to DGPS receiver with correct data.
  • SBAS will transmit the pulse to Sat-C satellite and those will revert the signal to receiver
  • The receiver use this to correct his own GPS receiver
48
Q

E) List errors in GPS System

A
  • Satellite clock error
  • Satellite Orbital error
  • Ionosphere Delay error
  • Troposphere delay error
  • Receiver clock error
  • Receiver noise Error
  • Multi Path error
49
Q

F) Describe any two GPS errors

A
  • Satellite clock error - drift in the satellites ceasium clocks allows errors of up to 1.5 metres
  • Satellite Orbital error - errors creep in between updates of the almanac of data
  • Ionosphere Delay error - A different ionization of the ionosphere particles can bend/disturb the signal traveling from the GPS to the Receiver
  • Troposphere delay error - area of earths atmosphere at different temperature and pressure which causes very small errors
  • Receiver clock error
  • Receiver noise Error - interfering radio transmissions
  • Multi Path error - mountains, buildings, bridges and other vessels can reflect the signal causing more than one signal.
50
Q

MOCK 6 Answers (Part B)

A
51
Q

AIS

A
52
Q

A) What does AIS stand for? (1)

A

Automatic Identification System

53
Q

B) What Frequency does AIS operate on? (1)

A

VHF

54
Q

C) List items that would be on a class A AIS dynamic data transmission (5)

A

Transmitted every 2” to 10”

  • Vessel position
  • COG & SOG
  • Rate of turn (ROT)
  • Navigation Status
  • True heading
55
Q

D) List items that would be on a class A AIS static data transmission (5)

A

Transmitted every 6 minutes

  • Name
  • Call Sign
  • MMSI
  • Type of vessel
  • Length
  • Breadth
56
Q

E) List items that would be on a class A AIS Voyage data transmission (4)

A

Transmitted every 6’

  • Destination
  • Previous port
  • ETA
  • Person on board
  • Type of Cargo
  • Draught
  • Navigational status
  • can send short securite messages
57
Q

F) What does the term “SOTDMA” means and how does it work (3)

A
  • Self Organise Time Division Multiple Access
  • Is a system that pre allocate Class A AIS future transmission slot
58
Q

G) Can AIS be used for IRCPS? (1)

A

No, as rely on other vessel equipment, but can increase situational awareness

59
Q

ECHOSOUNDER

A
60
Q

A) Draw a diagram of the key components of the marine echo sounder (4)

A
61
Q

B) How would multiple echoes appear on an echo sounder display and when would they be most luckily to occur? (3)

A
  • Will appear in shallow water when using the too high frequency
  • where seabed are more reflective
62
Q

C) Where on a ship should a transducer be located? (2)

A
  • Need to be located amidship, about at 1/3 from the bow, close to the center line, away from possible interference (turbulence, electrical) and troughs-hull opening
63
Q

D) Describe the setup of an echo sounder up for the best performance in shallow water and deep water ? (4)

A
  • 50 KHz would be better for deeper water as will use a longer pulse length and this will travel further than a shorter pulse and use a wider cone
  • 200 KHz would be better for shallow water uses short pulse and the cone is narrower
64
Q

IMPELLOR LOG

A
65
Q

E) Explain how speed is calculated from an impellor log (3)

A
  • A impeller will rotate with the water flow
  • a pick-up sensor will count the every impeller turn with the magnet on it
  • As this rotation is a know ratio distance, we can calculate the distance (from the rotation) x Time, we get the speed
66
Q

F) What are the advantages and disadvantages of an impellor log (4)

A

Advantages

  • cheap
  • Simple
  • work at slow speed
  • is retrievable

Disadvantages

  • Suffer for marine growth
  • Need regular check for accuracy
  • Easy to brake
67
Q

MAGNETC COMPASS

A
68
Q

A) List 5 Circumstances when the magnetic compass should be checked and adjusted (5)

A
  • On build
  • Every 2 years
  • Major items added or removed
  • Works onboard the vessel such us welding
  • Fire or damage onboard
  • Whenever is notice an error or the deviation car are not correct
  • Major change in latitude
  • Vessel is long time alongside
69
Q

B) What are the causes of permanent deviation and how are they corrected for in a marine compass? (3)

A
  • Is the entire influence on the compass from all the combined part of your vessel sach us: Engine, Generators, Anchor, Hull, Etc.
  • Addition of longitudinal and transverse correcting magnets placed in compass binnacle
70
Q

C) What are the causes of induced deviation and how are they corrected on a marine compass? (3)

A
  • Build of a charge from the heart magnetic field accumulating in any ferrous material of the vessel
  • On marine compasses is corrected using soft Iron Kelvins Balls and Flinders bar.
  • If the vessel has an aft bridge the bar need to be fit forward and for a forward bridge the bar would be fitted aft
71
Q

D) Is a Marine Gyro compass affected by variation or deviation? (2)

A
  • No as the true nord is obtained by the principle of gyroscopic proprieties
  • Gyro can have errors but will be of a different nature than Magnetic
72
Q

E) Why does a Gyro compass require a GPS input? (1)

A

To correct for Lat Error

73
Q

F) How does a GPS compass work? (2)

A

Recipe a signal from a satellite to 3 antennas and compares the location in relation to each other

74
Q

G) What are the advantages and disadvantages of the GPS compass? (4)

A

Advantages

  • Cheaper than a Gyro
  • Not effected by Magnetism (Variation and Deviation)
  • No moving parts
  • No effected by Lat Error
  • Work better at higher latitude

Disadvantages

  • Rely on GPS

NAV&RADAR MCA (11 decks)

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