How often is AIS information received?

AIS data is transmitted from vessels at a variety of rates. Class A ships send position updates every 2 - 10 seconds depending on their speed and rate of turn, or every 3 minutes when reporting as anchored/moored and not moving faster than 3 knots. Class B ships send position reports every 30 seconds when moving faster than 2 knots, otherwise it drops back to every 3 minutes. Information that doesn't change frequently, such as the vessel's name, size and voyage information, is sent every 6 minutes for both Class A and B.

The WatchMate continuously updates bearing, range, CPA, and TCPA for every vessel whenever a new position is received from the vessel and also whenever your vessel moves. In addition, the WatchMate displays the time that has elapsed since each vessel has sent its last update. This is useful to help you determine the currency and accuracy of the data presented.

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