I'm from Florida and visiting North Carolina, Tennesee. I'm not use to flying around or near mountains. Do they cause interference with GPS or Compass? Also, if I were to launch my P3 off the top of the mountain will going off the cliff have any effect on the VPS. I heard some stories where people have had their drone plummit to the ground after flying off the cliff. Should I keep VPS on or off? Any advice counts and please only give advice if you have experience flying near or on mountains. Thanks!