The position of any vessel that transmits AIS signals gets recorded on the MarineTraffic AIS loggers whenever new AIS information becomes available! The whole process of picking up, decoding and presenting this data on the MarineTraffic website is quick and effective resulting in near real-time depiction. In this article, you can learn more information on the frequency in which MarineTraffic receives AIS transmitted data.
The key factors that affect the overall frequency of the transmitted AIS information are the type of the AIS transponder (Class A or B) and the moving status of the subject vessel, as shown in the following table.
|Transponder Type||Vessel's Moving Status (Transponder ON)||AIS Transmission Rate|
|Class A||Anchored / Moored||Every 3 Minutes|
|Class A||Sailing 0-14 knots||Every 10 Seconds|
|Class A||Sailing 14-23 knots||Every 6 Seconds|
|Class A||Sailing 0-14 knots and changing course||Every 3.33 Seconds|
|Class A||Sailing 14-23 knots and changing course||Every 2 Seconds|
|Class A||Sailing faster than 23 knots||Every 2 Seconds|
|Class A||Sailing faster than 23 knots and changing course||Every 2 Seconds|
|Class B||Stopped or sailing up to 2 knots||Every 3 Minutes|
|Class B||Sailing faster than 2 knots||Every 30 Seconds|
Also, the update frequency of the incoming data depends on whether the AIS signal can be picked up by a terrestrial AIS-receiving station or not.
- Vessels that sail within the range of the MarineTraffic network of AIS-receiving stations get frequent updates in near real-time.
- Signals from vessels that sail in remote areas can only be covered using Satellite AIS. The positional updates provided by this service may vary from a few minutes up to several hours (regardless of how often the subject vessel transmits positions). On average, we get one position update per hour for ocean-going vessels equipped with a Class-A AIS transponder.
To ensure fast handling, accurate depiction and effective management of the incoming information, MarineTraffic uses proprietary downsampling techniques that take all of the above-mentioned factors into account. As a rule of thumb, in-range vessels will be updated on a 60-second basis (1 position report per MMSI per minute). The Live Map (and the other website pages) update accordingly. AIS positions get stored in the database likewise. The frequency of stored positions for older data (exceeding 3 months) gets scarcer (3 to 20 minutes based on the subject vessel's moving status).