Navigation General · AIS
A vessel's AIS transponder transmits position reports. Under which of the following conditions will a Class A AIS update its dynamic position data most FREQUENTLY?
- AWhen the vessel is at anchor with no heading change
- BWhen the vessel is underway at 20 knots and altering course✓ Correct
- CWhen the vessel is moored at a berth and the transponder is in low-power mode
- DWhen the vessel is proceeding at 5 knots on a steady course
Explanation
Class A AIS dynamic reporting intervals are speed- and maneuver-dependent. A vessel underway at high speed (14–23 knots) transmits every 2 seconds; while changing course at any speed the interval is also 2 seconds. At anchor the interval is 3 minutes (or 10 minutes if not moving), and at 5 knots on a steady course the interval is 10 seconds. The most frequent reporting occurs during high-speed course changes.
Authority: Bowditch (Pub. 9), Ch. 13
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