Over the weekend, some family and friends came down to visit us on the Isle of Wight, and stopped a mile or so away in a hotel in Seaview overlooking the Solent. With binoculars in hand, the sea view rooms looked out onto the passing sea traffic - ferries to France, cruise liners going in to Southampton, warships heading for Portsmouth and all manner of freightliners heading for who knows where.

To add to the seaside experience, the hotel menu also posts times of when the cruise ships are passing by so you can look out for them over dinner! These details are also posted in the Island's local newspaper and are presumably "public information".

Now one of the things that I love about the way the web is going is that it's getting easier to access "live data". From traintimes, to what's on the telly now, from roadworks on the M1, to the latest share prices, I can increasingly find out "what's happening now". So I had a look around to see if live shipping data is available from anywhere.

Now it turns out that it is, and it's provided by a system called AIS, the Automatic Identification System. It apparently works like this: each AIS enabled ship has an AIS transponder that incorporates: VHF receivers for receiving AIS information from other ships; a unit that provides integratoin with other shipboard systems (such as GPS and navigation systems); and a transmitter that transmits AIS data. (For a more technical description, there's a "how it works" explanation on the US Coastguard website.)

The transmitted AIS data includes at least a unique identifier for the vessel, location information, and the heading, course and speed information. This information can then be displayed on a map or other location revealing display.

Anyone with an appropriate receiver can receive the AIS data, and with a little bit of tinkering they can then display this information on a map. And it turns out that some enterprising folks around the Solent have done just that: Solent Area Ship Tracking.

Each balloon represents a separate vessel, as identified from its AIS data. So next time family and friends are down, and staying in Seaview, I can point them to the live shipping data map and they can find out a little bit more about each ship as it passes by :-)

Just a note of warning though - checking ship locations using a web based service like this should not be relied on if you're out sailing - the data may be stale (that is, out-of-date) or cached by your browser. The only guaranteed true picture will be one where you have grabbed the AIS data yourself from over the airwaves and then plotted it out, at the time, yourself...

The story isn't quite finished though. Firstly, there's a prequel as to how I found the map - rather than doing a badly specified websearch, (I didn't know AIS existed a week ago!) I asked a question on Twitter. Twitter? A web based short messaging service that sits somewhere between instant messaging, email and SMS text messaging! (For a quick tutorial, see this CommonCraft video: Twitter in Plain English.)

[video by Commoncraft]

As with many other social networking sites, Twitter supports "friending", in the sense of following the posts that other people make. So I posted a question in the hope that some of the people from the Isle of Wight I follow (and who follow me) would know whether such a map exists. And they did, and so that's how I got the link to the map shown above!

And secondly? Secondly there's a wishlist item for something I'd like to be able to see (and do). A way of uploading a photograph of each a ship to the web, tagging it in some way, and then being able to click on the marker for that vessel and see the photos of it (ideally along with a timestamp and location data from where the boat was when the picture was taken). Then it would be possible to 'anecdotally' start plotting out the route taken by each ship, and for the container ships, maybe even how laden it was entering and leaving each port!

PS the thought of tracking a ship as it circumnavigates the globe reminded me of an 'experiment' being run by the BBC at the moment to track a shipping container over the course of a year - you can find out more here: The Box.