Nice breakthrough in A.I.S.

Last night was pitch dark in Cork, the harbour waters were almost
IMG 1041spooky, black waters and no light. The moon is on a waxing crescent right now, and we merely had a ten percent moonlight last night. It reminded me of that year I was based with my regiment in French Guyana and during exercises we would sail at full speed in the dark with nothing but stars to guide us. Now technology have improved... In the comfort of my study at home, I was listening to harbour operations on my scanner and decided I would test my new AIS receiver.


Screen Shot 2012-01-26 at 13.00.44A.I.S., for those who aren't too familiar with it, stands for Automatic Identification System. It is not a RADAR at all, in fact it would rather be the opposite. Large commercial vessels over 300 tons and all passenger vessels, by law, should all have one aboard. Basically the A.I.S. transmitter is connected to the GPS (or has its own independent GPS chip embedded) and keeps broadcasting every few second a radio message on channels 87 and 88, giving loads of information that are very useful when you are sailing in a pitch dark night and want to avoid a close encounter with a supertanker...

Basicaly the data received by the AIS unit are encoded in NMEA IMG 1040sentences (64-bit plain text). A sample is shown below:


Messages include the following three basic types:

1. Dynamic Information, such as vessel's position, speed, current status, course and rate of turn.

2. Static Information, such as vessel's name, IMO number, MMSI number, dimensions.

3. Voyage-specific Information, such as destination, ETA and draught.

Read this very interesting page if you want to familiarise yourself with A.I.S.


Tonight I am playing with RadarGadget (Mirrorbow Technologies Ltd) which is almost 100% software based.Screen Shot 2012-01-26 at 13.03.16 It looks like a USB memory stick and all it does is to grab the radio signal, demodulate it, and if you are equipped with a plotting software like Polar Navy, Shipplotter, or AIS Dispatcher for example, you will see vessels around you moving. Mind you, you won't pick a container half submerged or a storm because A.I.S. is not a radar, all it does is grabbing a radio signal broadcasted by another vessel. Most sailing vessels in Ireland don't have any... Skippers don't want the good wife to know where they are, maybe...


IMG 1042Anyway, this USB A.I.S. is the smallest of its kind. I should have a small stock at my
workshop in the next couple of weeks. I have tested it successfully on Windows 7 and Mac OS-X, but later this week I will have a go at Linux Centos. I am planning to demo it during our Marine I.T. Course in NMCI. Most A.I.S. devices on the market are serial port, some are USB, most are designed for recreational use and usually a bit bulky. This one fits in your pocket. Down side is, it's a bit fragile where it connects with the antenna cable. So I use my two way radio antenna instead. Simply brilliant... and affordable too!


Feel free to call to the workshop to see one if you are interested... They can be fitted to your laptop in less than an hour in most cases.

I will definitely recommend those devices to the students in the Marine Data Communication Course!