Welcome Cruise Ship 🇧🇲Grand Princess Enjoy San Francisco

Hi! It is a real bot. All major ships transmit AIS [1] messages that can be received with a cheap antenna and receiver. I wrote a parser and tools [2] for the protocol. I have pals [3] with an office near the water [4]. That receiver is part of a data commons [5], giving me access to data on other ships. The bot then filters that feed (50m messages/day), looking for major ships passing through the Golden Gate [6]. When something goes through, it tweets an announcement.

Photos are all contributed by fans. I've thought about setting up an automated camera, but that requires an actual good view, which is trickier to acquire.

The big surprise for me was how much garbage data there is flowing through that system. Poorly maintained transmitters. Badly configured devices. And merchant marine sailors typing stuff into bridge systems definitely don't share my fussiness when it comes to getting data right. A lot of the code is just a huge set of regexs to turn what people type in the destination field into clean, consistent geographical names. (And if you scroll back some, it's definitely not perfect yet.) But since most of the data is intended to provide human-viewed radar-like displays, it works out fine in practice.

Another thing I learned is that marine geography is just different than how landlubbers see the world. In the same way we see the land as full of detail and the water as a vague blue area on the map, they have a lot of specificity for the water and its edge. But documentation of their notion of geography is much less available. So I've had to do a lot of manual work to figure out what a sailor means by, say, SFO, and there's still more to go.

Is that helpful?

[1] https://en.wikipedia.org/wiki/Automatic_identification_syste...

[2] https://github.com/wpietri/simpleais

[3] http://longnow.org/

[4] https://fortmason.org/

[5] http://www.aishub.net/stations/2161

[6] https://en.wikipedia.org/wiki/Golden_Gate