AIS and radar answer different questions. Here's how they complement each other.
Both track vessels, but they are not interchangeable. AIS tells you who and where from a vessel's own broadcast; radar tells you something is there from a reflected signal.
AIS carries the vessel's identity (MMSI, name, type), GPS position, speed and course. It reaches far beyond line of sight via relays and satellites, and it is what powers historical replay and voyage reconstruction. Its blind spot: vessels that do not transmit (see dark ships).
Radar sees objects with no transponder — small craft, debris, weather — but gives no identity and is limited to the horizon. It is a real-time, on-board collision-avoidance tool.
Modern bridges overlay both. For fleet ops, claims, and analytics off the water, AIS is the data layer — queryable, historical, and exportable. Try the API.