Shortly after publishing my iOS 4 jailbreak last October[1], I got to work on my next hobby project: a from-scratch homebrew GPS receiver, which can solve the user’s location solely from billions of radio antenna samples.
I took a commodity SDR (alongside the Python standard library and numpy) and built a signal processing pipeline that can detect and track GPS satellites over many minutes, drop and pick up satellites as they come in and out of view, and precisely determine the user’s position and clock inaccuracy.
All told, gypsum can go from a cold start to a fix on the user’s position, and the precise time, in less than a minute of listening to the antenna. I went on a journey of learning how to detect and track satellite signals that are literally too quiet to hear, and I hope that some of the magic comes through in the posts!
After implementing this myself and walking the long road of getting it working, I’m left completely stunned by the brilliance of GPS, across so many axes. I hope you enjoy the read!
On a more personal note, I’ll be starting a new job next week which isn’t as amenable to publishing side projects, and therefore this will be my last publicly-published project for some time. I’ve had great experiences making and sharing projects on here, and I’m really grateful for the positive feedback that’s been shared!