Chris Hadfield is one of the Astronauts currently on board the International Space Station. He tweets a lot about life above the earth as he orbits our planet at a speed of just under 8km per second.

As I’m interested in astronomy and space-related stuff, I was idly wondering how easy it would be to map where Chris has tweeted from… he must surely be one of the most pan-global twitter users there is.

Many people choose to geo-code their tweets, showing readers where they were when they hit the tweet button. Chris’s tweets don’t include a position, but being on board a spacecraft with a regular orbit means it should be possible to reverse-engineer his location from the time each tweet was sent.

Heres a a little web-app I built which shows 800 of Commander Hadfields tweets and where the ISS was at the time the tweet was sent. (It requires a WebGL capable browser – if you don’t have one then heres a YouTube video of what you would have seen).

(for the technical amongst you….)

There were three components to building this…

1. Request a bunch of tweets from the twitter api – when these are returned, they include a UTC time which represents when the tweet was created.

2. Work out where the ISS was at the time the tweet was created. This turned out to be somewhat more difficult than I hoped, but I learned a huge amount about NORAD, orbital data, and spaceflight mathematics in the process.

3. Plot the positions on a spinning globe. To do this I used the excellent open source WebGL Earth library, which made the actual animation part of the project relatively simple.

So… is it useful?… probably not, but it made for a nice little side project.