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OOW 3000 > Navigation Equipment > Flashcards

Navigation Equipment Flashcards

1
Q

How does an echo sounder work?

A
  • Transmitter generates pulse
  • Transducer sends acoustic pulse
  • Echo recieved by reciever
  • Display shows depth
  • Time difference calculated
    Depth = (Speed of Sound × Time) / 2
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2
Q

What are the errors of an echo sounder?

A
  • Shoals of fish
  • Seaweed
  • Side echoes
  • Noise error
  • Aeration error
  • Propagation error
  • Density error
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3
Q

What is the best setup of an echo sounder in shallow and deep water?

A

Shallow water - 200 KHz shorter pulse

Deep water - 50KHz longer pulse

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4
Q

What are some different types of speed logs?

A
  • Impeller log
  • Electromagnetic log
  • Pressure tube log
  • Doppler log
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5
Q

Which logs show STW and which show SOG?

A

All the logs show STW apart from the doppler log which can show SOG as well

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6
Q

How does the Doppler log work?

A
  • Transmits acoustic pulse at known frequency
  • Compares the difference in change of frequency
  • Change in frequency proportional to speed
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7
Q

What is the janus configuration?

A

Can also return side movement, only on doppler log

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8
Q

When is it important to be able to switch into hand steering?

A

A qualified helms person must be immediately available to to take over at all times

  • Areas of high density traffic
  • Restricted visibility
  • When ship manoeuvring is critical
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9
Q

What is autopilot track control?

A

The vessel is kept on a pre-determined track and uses an input from satellite navigation system

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10
Q

What is autopilot heading control?

A

Set the course into the autopilot. Set course is then compared to gyro compass and if there is a difference then the rudder command signal brings the ship back on course.

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11
Q

What are the requirements for testing steering?

A
  • Test manual steering once a day and before entering restricted waters
  • Test steering gear at least 12 hours before departure
  • Log all steering gear tests, checks and emergency steering drills in the Official Logbook
  • Emergency steering gear test every 3 months
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12
Q

What are the features of autopilot?

A
  • Rudder limit sets the angle applied by automatic control
  • Rudder controls the number of degrees the rudder will move to correct every degree of heading error e.g. with control set to 3, the rudder will move 3° for every 1° of heading error
  • Counter rudder is the amount of opposite helm to be applied
  • Weather control to counteract the effect of weather and sea conditions, time delay so ship will recover naturally when under repetitive yaw
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13
Q

What is BNWAS?

A

Bridge Navigational Watch Alarm System

  • Monitors bridge activity and OOW awareness and can detect operator disability
  • Uses stages of visual and audible alarms to alert bridge team if they do not respond appropriate personnel will be automatically alerted
  • Shouldn’t distract the OOW from watch keeping duties
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14
Q

What is AIS?

A

Automatic Identification System

  • Automated tracking system that displays other vessels in the vicinity
  • Works on VHF frequency
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15
Q

What is the purpose of AIS?

A
  • Help identify vessels
  • Assist in target tracking
  • Simplify information exchange
  • Provide additional information to increase situation awareness
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16
Q

Which vessels are required to have AIS under the IMO and SOLAS regulations?

A

International voyaging ships of 300 GT or more and all passenger ships regardless of size

17
Q

What do the COLREGS say about AIS?

A

There is no provision for the use of AIS in the COLREGS so decisions should be made using radar information or visually.

18
Q

What are the limitations of AIS?

A
  • Some vessels may switch off their AIS either illegally or in certain circumstances by judgment of the captain
  • Accuracy of information received is only as good as accuracy of information transmitted
  • OOW should be aware that poorly calibrated ship sensors might lead to incorrect information being transmitted
  • If no sensor is installed or the sensor fails to provide data the AIS automatically transmits the ‘not available’ data value, the built in integrity check cannot validate the contents of the data processed
19
Q

What is static AIS data?

A
  • Transmitted every 6 mins
  • MMSI number
  • Call sign and name
  • IMO number
  • Length and beam
  • Type of ship
  • Location of GPS antenna
20
Q

What is dynamic AIS data?

A
  • Transmitted every 2-12 seconds and every 3 mins at anchor
  • Vessels position
  • COG
  • SOG
  • Heading
  • Nav Status
  • ROT
21
Q

What is AIS voyage data?

A
  • Transmitted every 6 minutes
  • Ships draught
  • Hazardous cargo
  • Destination and ETA
  • Persons on board
22
Q

What is Class A AIS?

A

Mandated for all vessels 300 GT and above engaged on international voyages as well as all passenger ships

23
Q

What is Class B AIS?

A

Provides limited functionality and is intended for non-SOLAS vessels. Primarily used for vessels such as pleasure crafts

  • It is only required to recieve, not transmit, text safety messages
  • Has reporting rate less than Class A

Does not transmit the following:

  • IMO number + callsign
  • Destination + ETA
  • Navigational status
  • ROT info
  • Draught
24
Q

What is SOTDMA?

A

Self Organise Time Division Multiple Access

System that pre allocates Class A AIS future transmission slot

25
Q

What inputs does AIS need?

A
  • VHF Antenna
  • GPS
  • Speed log
  • Gyro
  • ROT
26
Q

What are the advantages of a doppler log over an electro magnetic log?

A
  • Yields STW as well as SOG
  • Not susceptible to hull shape irregularities
  • Better in pitching and rolling
  • More resistant to fouling and aeration
  • Better at low speed and berthing/reversing
27
Q

What navigation equipment should all ships, irrespective of size carry in board?

A
  • Magnetic compass
  • Pelorus or compass bearing device
  • Nautical charts or ECDIS depending on size
  • A GNSS receiver
  • Radar reflector
  • Sound reception system
  • Telephone to emergency steering

OOW 3000 (23 decks)

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