The automatic identification system (AIS) is an automatic tracking system on ships and vessels. It provides information such as unique identification, position, course, and speed. AIS is intended to allow ships to view marine traffic in their area and to be seen by that traffic.
Digitraffic service provides A class position and metadata messages. Some AIS-messages are filtered or modified.
Fishing vessels
All fishing vessels (vessel type 30) are filtered out from the AIS-messages.
Vessel type
Vessel types and cargo descriptions are modified with following rules.
| Original value | Modified value | Vessel type |
| 0 | 0 | Default value or type not in use |
| 1 - 19 | keep original value | Reserved for future use |
| 20 - 29 | 20 | Wing in ground (WIG) |
| 30 - 39 | keep original value | 31 - 32 Tug (towing) 33 Dredging, underwater operations 34 diving operations 35 Military 36 Sailing 37 Pleasure craft |
| 40 - 49 | 40 | High speed craft (HSC) |
| 50 - 59 | keep original value | 50 Pilot 51 Search and rescue 52 Tug 53 Port tender 54 Anti pollution 55 Law enforcement 56 - 59 Other |
| 60 - 69 | 60 | Passenger |
| 70 - 79 | 70 | Cargo |
| 80 - 89 | 80 | Tanker |
| 90 - 99 | 90 | Other |
| > 99 | keep original value | Reserved for future use |