From GPS Coordinates to Screen Pixels: The Full AR Projection Math

I've been building an Android app that overlays aircraft labels on a live camera feed when you point your phone at the sky. You fetch a plane's position from an ADS-B API, you have your own GPS location, and the goal is to draw a label at the correct pixel on screen. The problem sounds straightforward until you try to implement it. There are four distinct coordinate spaces between the aircraft's GPS position and that pixel. Wrong output, no exception, no warning. The math compiles fine either wa