I'm actually serving data to marinetraffic.com from a receiver near Point Conception, California. The AIS broadcasts in the VHF band so it's basically line of site, plus a bit more because of various scattering effects. We have a receiver on Santa Cruz Island at about 750 ft elevation that gets AIS signals from ships off Mexico (when the conditions are right) - way beyond the quoted range.
The amount of shipping along even our small section of coast boggles the mind. There's a seasonal signal to it also. See [1] for example.
This makes me want to buy a bunch of AIS receivers and take a week or two off to travel to far flung locations to setup remote receiving locations.
We've been putting them at our HF radar sites to log ship data, so that we can use the ship data in a hack to get the radars to self calibrate. The radars measure ocean currents and are in some pretty 'far flung locations'. Yes it's fun!
Besides the fun this is, setting up the recievers I mean, great hack with the self-calibrating radars, elegant and effetive, respect!
Maybe one should integrate ship data to freight tracking services, so you can actually locate your container, well more the vessel!
For those that are not aware, this is crowd sourced aggregation of data received by AIS (Automatic Identification System) VHF receivers which are hosted by volunteers who put up a receiver, antenna, and send the data received from the ships to this site.
At Bloomberg, we provide the same live vessel position via the BMAP function on the terminal mainly so that oil / natural gas traders can monitor and speculate commodities flows based on ship traffic and reported contents of ships. Someone posted a screenshot on this Quora question:
It is definitely fun to play around with. Similar tools are provided to slice/dice the data to look at all the vessels which match particular criteria.
Similarly, all the data for positions of critical infrastructure (refineries, oil pipelines, power plants, etc) are provided as well as live storm tracking information so traders can determine if natural disasters will affect particular sectors or companies.
Very nice, but I had to wonder why, of the thousands of ships whose positions are recorded, only 2 appear to be any significant distance from land. The answer is in the FAQ [1]:
> The MarineTraffic system does not cover all the seas of the world, but only specific coastal areas where a land-based AIS receiver is installed.
The AIS transmissions are VHF (162MHz) so they are fairly short range, although with high gain antennas you can extend it a bit (with a corner reflector I once had intermittent data from a ship 600nm away).
Often tankers sit out and wait for the oil price to change marginally (yes, really - its that silly). Other than that, could be many reasons including bunkering (via smaller ships), full port, repairs/servicing, etc.
It's not that silly when you work it out. You have a ship holding 2-3 million barrels of oil and a 20-40 crew. It looks like the market price of light sweet crude varies by as much as $1 per barrel per day. Which means a difference of 2-3 million dollars if you come to port today instead of yesterday.
Yeah after reading the FAQ I came to the same conclusion. But also realized that pirates wouldn't actually need this site and could just get their own AIS receiver's
Those are mostly oil tankers. Since 20% of the world's oil passes through the Strait of Hormuz [1], the Iranians threat of closing that passage has petroleum prices recently. More analysis at The Oil Drum [2].
This site is really cool. Everyone interested in this sort of tracking should checkout PlanePlotter from COAA http://www.coaa.co.uk/planeplotter.htm. It does a similar sort of thing but for planes which have ADS-B transmitters and a team of volunteers sharing data. It costs 25 euros to access the shared data but well worth the money (I'm not affiliated just a happy customer).
It really needs a shaded overlay or similar that shows the coverage regions. If you don't know that a patch of sea isn't being monitored, it's not exactly reliable data.
In the popup for a particular boat click "Show Vessel's Track" which appears to show a set of previous position reports with a line drawn between them.
I built an app that combines freely available AIS data with other relevant inventory data and sell subscriptions to some local oil-spill recovery companies: http://demo.dedicatedmaps.com/
The amount of shipping along even our small section of coast boggles the mind. There's a seasonal signal to it also. See [1] for example.
[1] http://www.calculatedriskblog.com/2011/10/la-port-traffic-in...