AIS (Automatic Identification System)
AIS is a transponder system for ships intending to increase the safety at sea. It operates in the VHF band. The two frequencies used worldwide are 161.975 and 162.025 MHz (channels 87B and 88B, or AIS1 and AIS2).
An AIS transmitter regularly transmits the ship's position, heading, speed and MMSI (the unique maritime identification number). This data is received by ships in the vicinity. The data can be plotted automatically on a digital map or radar screen.
Every 2 - 10 seconds, a ship equipped with AIS e.g. transmits the following data:
Ships broadcast all information alternating between the two channels.
To receive AIS, there are several options:
Option 1: PC with soundcard
Be advised that your receiver should not be scanning when you want to receive AIS, since it would miss AIS transmissions (hence ships) while scanning other frequencies. Tune your radio to either one AIS frequency.
If you use a marine VHF, it should be on channel 87 or 88 constantly. Since it can't be used for normal traffic while monitoring AIS, it is advisable to use a (cheap) scanner or a second marine VHF for AIS. Further to that, not all marine VHF equipment is suited to receive AIS.
Option 2: PC with serial port
The interfaces on this site are meant for paging. They can't be used for AIS.
Option 3: InternetYou're far from the nearest port or the coast? Or you don't want to do it yourself? Several internet sites offer AIS information. A good choice is www.vesseltracker.com.
Left, you see a recent image that I received on the east side of Rotterdam. Click on the image to get a full-sceen version. The time shown top left is UTC.
If you registered Shipplotter, you can see what other people receive by selecting the "Sharing' option, while other people can see the ships that you receive.
Rotterdam, 25 Feb 2018 16:18 CET
To monitor the performance of your system and to compare different receivers or antennas, you can use ShipPlotter.xls. This Excel-file, programmed by Neal Arundale, is run from the same directory containing shipplotter.exe.
It shows the number of ships in range and AIS messages received per minute (left vertical axis) and the reception range (right vertical axis).
For a reliable overview of most European and worldwide ports, I recommend www.vesseltracker.com. Apart from a detailed overview of shipping traffic, Vesseltracker offers historical data and photo's of individual vessels.