That is cool, I didnt know that about GPS. I am not a developer obviously but I help developers understand what to do, so it got my brain wondering.GPS also give altitude. Trilateration works by giving X,Y and Z axis. X,Y being horizontal (lat long) and Z gives altitude. It's based off timing from the GPS constellation. Nerd math but it works. Just pre-program flight paths and everything is synched (as long as there's no atmospheric scintillation or other space weather)