Navigation Systems Flashcards

What does AIS stand for in the context of vessel traffic management?

Answer: Automated Identification System

AIS (Automated Identification System) transmits vessel identity, position, course, and speed to other ships and VTS centers.

A vessel reports its position as 'at anchor in the anchorage.' On radar, the VTS operator notices the vessel is slowly drifting. What is the most likely cause?

Answer: The vessel is dragging anchor

A vessel at anchor that shows movement on radar is most likely dragging its anchor, which requires immediate VTS action.

Which AIS message type is used to broadcast safety-related text messages to vessels?

Answer: Message 14

AIS Message Type 14 is the Safety Related Broadcast Message used to transmit text-based safety information to all vessels.

What is the primary purpose of a VHF Direction Finding (VHF/DF) system in a VTS center?

Answer: To determine the bearing of a transmitting vessel

VHF/DF enables the VTS operator to determine the compass bearing from which a VHF transmission is originating, helping to locate vessels.

On a radar display, what does a vessel's 'trail' or 'tail' indicate?

Answer: The vessel's recent track history

A radar trail or tail shows the recent path a vessel has traveled, helping the operator assess its course and speed over time.

What is the significance of MMSI in a VTS context?

Answer: It uniquely identifies a vessel for AIS and DSC communications

The Maritime Mobile Service Identity (MMSI) is a unique nine-digit number that identifies a vessel in AIS transmissions and DSC distress calls.

A radar target that shows no AIS correlation is called what in VTS terminology?

Answer: A 'sleeping' or unmatched target

A radar contact with no corresponding AIS signal is referred to as a sleeping or unmatched target, requiring investigation by the VTS operator.