An AIS position report is a dynamic data transmission conveying a vessel's current location, speed, course and navigational status at a specific timestamp. These messages provide essential movement and timing information derived from the transmitting station's connected position sensor, rather than constituting a complete picture of the vessel or its voyage.
The United States Coast Guard identifies Messages 1, 2 and 3 as Class A position reports, while Message 18 serves as the standard Class B position report. Position reporting intervals vary significantly by equipment class, speed, movement and reporting mode, meaning these updates normally arrive more frequently than static or voyage-related information.
A target's AIS position is derived from its electronic position-fixing receiver and may not coincide exactly with the target detected by radar. Consequently, the received report reflects the transmitting station's own data rather than an independent measurement of position.
