If I use litchi to program a mission with waypoints: Let's say I'm flying on a level field. If I set a waypoint to be negative 10 feet (-10), what would happen? Thanks
I neither have nor use Litchi so I will guess. Either the app will not allow use of a negative waypoint below level ground or, if it does, you can sell your Phantom for parts on eBay. Just my guess
in answer to OP question, your Phantom will crash into the ground - given the appropriate assumptions since you said it was a level field and presumably your takeoff point was at said field...