"Hi Randy, thanks for the detailed response! Yes i am a developer, but haven't yet got any experience working on ArduCopter etc, so far just DroneKit. I'll take a look at HIL_GPS, that sounds promising.
I'm currently using…"
"Hi Randy, I've read about VISION_POSITION_ESTIMATE, has it been implemented in Arducopter at all? It sounds like you're saying it hasn't, I wanted to check if I understood correctly, or if anything had changed since 2015."