VTS Equipment and Technology 2 — Questions and Answers
Question 1: What is the primary advantage of an S-band radar (3 GHz) over X-band radar (9 GHz) in a VTS center?
- Better target resolution in clear weather
- Superior performance in heavy rain and adverse weather (Correct answer)
- Shorter minimum detection range
- Higher accuracy for small vessel detection
Correct answer: Superior performance in heavy rain and adverse weather
S-band radar operates at a lower frequency which suffers less attenuation from rain and weather, making it preferable in adverse conditions.
Question 2: In AIS, what does a Class A transponder transmit that a Class B transponder does NOT?
- MMSI number and vessel name
- Rate of turn (ROT) and navigational status (Correct answer)
- Speed over ground and course over ground
- Latitude and longitude position
Correct answer: Rate of turn (ROT) and navigational status
Class A transponders transmit rate of turn (ROT) and navigational status fields, which are not included in Class B transmissions.
Question 3: A VTS operator notices a radar target has no associated AIS return. What is the MOST likely explanation?
- The vessel is traveling faster than 30 knots
- The vessel is not AIS-equipped or its transponder is off (Correct answer)
- The radar is operating on the wrong frequency
- The vessel is transiting a traffic separation scheme
Correct answer: The vessel is not AIS-equipped or its transponder is off
Radar can detect any vessel with sufficient reflectivity, while AIS requires an active transponder, so a radar-only target typically indicates no AIS equipment or a deactivated transponder.
Question 4: What type of VHF antenna configuration is typically used at VTS stations to achieve omnidirectional coverage of a harbor?
- Yagi directional array
- Collinear omnidirectional antenna (Correct answer)
- Parabolic dish antenna
- Log-periodic antenna
Correct answer: Collinear omnidirectional antenna
Collinear omnidirectional antennas provide 360-degree coverage with gain, making them ideal for VTS harbor communications.
Question 5: In a VTMIS (Vessel Traffic Management Information System), what is the function of sensor fusion?
- Combining radar and AIS data into a single tracked target (Correct answer)
- Fusing VHF audio channels into one broadcast
- Merging tide gauge readings with weather data
- Integrating CCTV feeds into the radar display
Correct answer: Combining radar and AIS data into a single tracked target
Sensor fusion correlates radar plots and AIS reports into a single composite track, giving operators a more complete and reliable picture of vessel movements.
Question 6: What is the purpose of a RAMARK in the context of VTS radar operations?
- A radar beacon that transmits continuously to identify a fixed position (Correct answer)
- A software marker placed on a radar screen by the operator
- A radar reflector mounted on a buoy
- A method of measuring radar range accuracy
Correct answer: A radar beacon that transmits continuously to identify a fixed position
A RAMARK (Radar Marker) is a radar beacon that transmits continuously, appearing as a radial line on radar displays to identify its position.
Question 7: When a VTS radar system experiences 'sea clutter,' what adjustment should the operator make?
- Increase transmitter power output
- Apply the STC (Sensitivity Time Control) or sea clutter control (Correct answer)
- Switch from X-band to S-band radar
- Reduce the radar antenna rotation speed
Correct answer: Apply the STC (Sensitivity Time Control) or sea clutter control
STC (Sensitivity Time Control) reduces receiver gain at short ranges where sea clutter is most intense, helping to distinguish real targets.
VTS Equipment and Technology 2
What is the primary advantage of an S-band radar (3 GHz) over X-band radar (9 GHz) in a VTS center?