VTS Equipment and Technology 5 — Questions and Answers
Question 1: What is the function of the DSC (Digital Selective Calling) controller integrated into a VTS VHF radio system?
- It automatically selects the strongest VHF channel for reception
- It enables direct digital calls to individual vessels by MMSI number and handles distress alerts (Correct answer)
- It converts analog VHF signals to digital format for recording
- It controls antenna switching between omnidirectional and directional modes
Correct answer: It enables direct digital calls to individual vessels by MMSI number and handles distress alerts
DSC allows VTS operators to place priority calls directly to specific vessels using their MMSI, and automatically receives distress alerts transmitted on Channel 70.
Question 2: In VTS radar, what does 'pulse length' affect in terms of radar performance?
- The rotation speed of the radar antenna
- The range resolution — shorter pulse lengths provide better range discrimination between close targets (Correct answer)
- The bearing accuracy of the radar system
- The maximum detection range regardless of target size
Correct answer: The range resolution — shorter pulse lengths provide better range discrimination between close targets
Shorter pulse lengths improve range resolution (ability to distinguish two targets at similar ranges), while longer pulses increase detection range but reduce resolution.
Question 3: What does the IMO performance standard require for the minimum range of an X-band VTS radar for detecting a small vessel with 10 m² radar cross-section?
- 1 nautical mile
- 3 nautical miles
- 8 nautical miles (Correct answer)
- 20 nautical miles
Correct answer: 8 nautical miles
IMO/ITU performance standards for VTS radars typically require detection of a 10 m² target at a minimum of 8 nautical miles in normal propagation conditions.
Question 4: A VTS operator's workstation displays 'Heading Line' data on AIS targets. What is the source of this information?
- The vessel's GPS receiver calculating heading from consecutive positions
- The vessel's gyrocompass or electronic heading sensor connected to the AIS transponder (Correct answer)
- The VTS radar calculating heading from target movement
- Satellite imagery processed at the VTS center
Correct answer: The vessel's gyrocompass or electronic heading sensor connected to the AIS transponder
AIS transmits true heading from the vessel's gyrocompass or heading sensor; this is distinct from course over ground which is GPS-derived.
Question 5: What is the primary function of a VTS meteorological sensor network (anemometers, visibility sensors)?
- To control vessel speed limits automatically based on wind readings
- To provide real-time environmental data that VTS operators relay to mariners for safe transit decisions (Correct answer)
- To trigger automatic port closure when visibility drops below 100 meters
- To power the VTS backup generator during storms
Correct answer: To provide real-time environmental data that VTS operators relay to mariners for safe transit decisions
Met sensors give VTS operators current visibility, wind speed/direction, and sea state data that they use to advise vessels and inform traffic management decisions.
Question 6: In the context of VTS data recording, what is an 'SDVR' (Shore-based Data and Voice Recorder) required to retain according to IALA guidelines?
- Voice communications only for 30 days minimum
- All sensor data, AIS tracks, radar replays, and voice recordings for a minimum of 30 days (Correct answer)
- Only incident-flagged communications for 1 year
- VHF channel 16 recordings only for 24 hours
Correct answer: All sensor data, AIS tracks, radar replays, and voice recordings for a minimum of 30 days
IALA guidelines recommend that VTS shore-based recorders retain all sensor data, radar, AIS, and audio for at least 30 days to support post-incident investigation.
Question 7: What is the purpose of 'track history' or 'track trail' displayed on a VTS radar or VTMIS screen?
- To predict where a vessel will be in the future based on its current speed and heading
- To show the past positions of a tracked target, allowing operators to assess its recent movement pattern (Correct answer)
- To display the vessel's planned route as filed with the port authority
- To highlight vessels that have deviated from the traffic separation scheme
Correct answer: To show the past positions of a tracked target, allowing operators to assess its recent movement pattern
Track history displays a series of past target positions as a trail, allowing operators to observe speed changes, course alterations, and unusual behavior patterns.
VTS Equipment and Technology 5
What is the function of the DSC (Digital Selective Calling) controller integrated into a VTS VHF radio system?