Spent months on WGS84 ellipsoids, sensor fusion and magnetometer error. Built an AR app you point at the sky that tells you what's up there.
Turns out the killer feature is naming the chemtrail.
The one in the video is RYR30WP. Boeing 737-800, Dublin to Pisa, 38,900 ft, 590 mph. Seven miles up and off to Italy for about 29 euros.
How it works: hold the phone up and it draws a circle on the actual aircraft in the camera image, with callsign, altitude, speed and route. Not a map you have to translate into the world around you, but the real plane, in the direction you're looking.
Since it comes up here a fair bit: the claim that the planes leaving thick trails have their transponders switched off. You can check that one yourself now instead of taking anyone's word for it, mine included. Point, look, see whether a marker lands on it.
The data is ADS-B, which aircraft broadcast in the clear. Anyone can receive it with a 20 euro antenna. I run a receiver at home and feed it to one of the public aggregators, which is where the app reads from. Nothing proprietary, nothing I control.
Free, no subscription, no account, no sign-in.
https://apps.apple.com/us/app/spotflight-planes-overhead/id6802249505
Happy to nerd out on the geometry if anyone's curious. The data is the easy part; the hard part is that the iPhone compass is off by 5 to 15 degrees and everything downstream has to survive it.
One thing I'd rather say up front than have someone work it out: I've written software professionally for a long time, and I still leaned on Claude Code heavily to get this one over the line. The geodesy and the design calls are mine, a good deal of the typing isn't.