AEGEAN RADAR · GUIDES

How to read an AIS position

1. Look at the time first. Every position has the time of the last message. Older than 15 minutes is marked delayed; the ship may be far away by now.
2. Identity. MMSI is the radio number of the ship; the first three digits show the flag. IMO, name and call sign come from a separate static message and may arrive later or be missing.
3. Speed and course. Speed over ground is in knots. Course over ground is where the ship moves; heading is where the bow points. They differ with wind and current.
4. Destination and ETA are typed in by the crew and are often out of date.
5. The track joins received positions with straight lines. It is not the exact route.

Not for navigation or collision avoidance.