  The Automatic Identification System (AIS) tracks vessel movement by means of
electronic exchange of navigation data between vessels, with onboard
transceiver, terrestrial and/or satellite base stations. The gathered data
contains a wealth of information useful for maritime safety, security and
efficiency. This paper surveys AIS data sources and relevant aspects of
navigation in which such data is or could be exploited for safety of seafaring,
namely traffic anomaly detection, route estimation, collision prediction and
path planning.
