Sun, 28/12/2008 - 00:18 — peterv

As I am preparing for the ROC VHF/SRC exam, I got more interested in marine electronics and safety systems. One aspect is that all new SOLAS ships over 300 gross tons since July 1, 2002 (and some other conditions as commercial passenger transport) must carry an AIS system (Automatic Identification System). This system will transmit (in channels 88A and 88B in the VHF range in GMSK, that is around 162 MHz) a signal that carries the position, course and speed of the vessel.

The fun thing is that some groups got into setting up a world-wide receiver network for this signals. Coverage is essentially line of sight based, so somewhere between 10 and 100 nautical miles (a nautical miles is approx. 1.8 km), depending on the height of the transmitting and receiving antennas. One I found with an open and free service is the site of marinetraffic http://www.marinetraffic.com/ais/default.aspx?centerx=3&centery=52&zoom=... that shows a lot of vessel coordinates. What strikes me is that they also display the entire recent ship route with the Show Vessel's Track feature and photo's.

So e.g., the ship depicted below (the "Grande Anversa") left the Verrebroekdok in Antwerp (51.2675 N, 004.2100 E) today (27 Dec 2008) around noon and is now halfway the Canal (52.35 N, 002.32 E) on it's way towards Portbury.

One more thing, when looking at the world view, there is anecdotic proof that the Canal (the sea passage South East of the UK) is indeed the most densely packed region with commercial ships. The square region shown on the World Map centered around 52.7 N, 4.2 E shows at this time 799 AIS sending ships (not all are moving, some are anchored).

Good to learn some safety communication before setting out to sea in this area.

An interesting side effect noted by p2 is that he can now better predict the timing and arrival of the Finnish ferries (Helsinki Rostock) with this system :-)

A slight potential disadvantage is noted in this text: http://www.uais.org/AISandnon-SOLASvessels.htm

... while raising questions with regards to security and illegal use of the system by pirates, to obtain detailed information on the ship’s cargo.