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Comment by hobbescotch | Hacker News Reader

Does anyone know where they get the data for these shipping map sites?

Modern vessels are required to have a AIS transponder. This is a radio that sends the ships speed, position, angle and optionally their destination around by marine (VHF) radio. These maps are probably made by having thousands of receivers recording the AIS data.

There are satellite networks that can pick up AIS broadcasts from almost anywhere on the planet. So you can track a ship in the middle of the ocean with a few minutes delay. Pretty amazing to imagine how many signals these satellites have to process at once and how weak they must be after making it all the way into space.

In this case, the underlying data is from exactEarth. It’s not free data. I believe exactEarth obtains the data by reading the pings from the ship’s transponders.

https://www.exactearth.com/product-exactearth-shipview

It’s free in the sense that there are projects where as long as you are operating an antenna feeding data, you get access to a feed of all data for free with the only restriction being you can’t compete by just restreaming the complete feed.

Oh that's interesting, thanks. So I guess it's similar to ADS-B exchange[1] and the like but for ships.

Have you operated an antenna, by chance? I've considered building an ADS-B receiver to satisfy my curiosity about the planes I see out my window all day.

[1] https://www.adsbexchange.com/

If you want to try the ADS-B receiver, you can do it for < $40. It's out of stock currently, but last year I bought the first one on this page https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/

I got busy with other things so haven't done much with it, but there are some Python libraries that made ADS-B easy.

This site [1] allows you to get their real time global feed if you push your local feed in exchange. AFAIR equipment costs a few hundred bucks tops. I think other sites like [2] offer to provide a base station. Not sure what data and licensing you get in exchange though.

[1] https://www.aishub.net/

[2] https://www.marinetraffic.com/

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