"You'll probably need RTK to get the path accuracy you need. It would be preferable to have an infrastructure system (internet subscription-type service) to save you the hassle of having to survey in each site.
"If it's steady in MANUAL mode, then that looks like your Pololu is pretty well configured. You were doing some nice slow movements. See if it oscillates if you do some fast short-travel oscillations (like the Pixhawk is commanding it to do).
"Hi, what's your steering actuator - is that off the shelf?
I'm far from an expert on the tractor side, but here are a few thoughts. Also, I don't know your background so apologies if any of this is telling you how to suck eggs.
1) What's the mapping…"
"Rob, the incoming air above the rotor is being drawn in from a larger area at a lower velocity than the air leaving the propeller - the streamtube contracts below the rotor so that you have constant mass flow but increased velocity.
"Sportjet, it may be simpler than you think. Dimension Engineering make some RC (PWM) controlled relays. Set up the channel on your controller, configure the APM to pass it through, and plug in the relay.
"Take this with a grain of salt - I haven't looked at the code in almost a year.
Hold sets throttle to RC_TRIM. That, in generally, wouldn't apply brakes but would depend on the ESC, usually it will just set you to "idle".