It would appear that for the last couple of weeks the AIS heading information on a vessel regularly visiting our port has been incorrect. This could result in some considerable confusion in a close quarters situation at sea.
We immediately contacted the ship’s manager, who contacted the ship. It transpired that the heading information being transmitted by AIS was about 25 degrees in error. The fault was rectified.
This highlights that, in assessing a traffic situation, absolute reliance should not be placed on the accuracy of information being transmitted by AIS, or on a single source of information. When possible, check the accuracy of the AIS data being transmitted by your vessel.