AIS Info
AIS stands for Automatic Identification System, this system is generally used on "large" ships (over 300 tons and passenger vessels).It is used for collision avoidance, navigation aid and search and rescue.
Each vessel has its own unique identification number called MMSI (Maritime Mobile Service Identity).
The vessel containing AIS sends out general information every 2 to 10 seconds containing:
- Navigational status
- Rate of turn
- Speed over ground
- Position
- Course over ground
- True Heading
- Time stamp (when the message was sendt)
- Type of ship
- It's cargo
- Dimension of the ship
- Draught of the ship
- Destination
- ETA (estimated time of arrival)
The messages are in binary and not easy to decode without special software or decoders.
There are 2 main AIS decoders for the PC: NASA AIS and the SR-161 AIS.
It is possible to decode the messages using a Scanner attached to a Soundcard and using ShipPlotter,
but the decoding is not nearly as good as a hardware AIS decoder.
My site uses an SR-161 AIS decoder and an ACR AIS-A3200 VHF antenna for these 2 frequency's.
The antenna is placed appr. 110 meters above sea-level for maximum coverage.
It is connected to a Debian Linux server with a custom Perl AIS parser.
The Perl program puts the data into a MySQL database and the website does the rest.
