Flying below Ground level in a Gorge with Waypoints

[White Airwolf]

Still trying to clear this matter up. Still confused.
If I'm at the top of a gorge say and I want to fly in the gorge, which is say 300 feet deep, do I set my return to home Fail safe to, say, 375 feet so if I lose reception, it will fly back to take off height and then initiate the RTH which is normally at 75 feet? Or will it go up 375 feet from where it is in the gorge before returning to home?
Can I also fly a mission with one of the apps such as DJI's or FPV Camera, Autoflight Logic etc with negative waypoints in the gorge? In other words, I want to take off from the top of the gorge and fly a mission through the gorge at negative altitude such as -100 feet. Will it work?

Thanks

 

[Scotflieger]

Still trying to clear this matter up. Still confused.
If I'm at the top of a gorge say and I want to fly in the gorge, which is say 300 feet deep, do I set my return to home Fail safe to, say, 375 feet so if I lose reception, it will fly back to take off height and then initiate the RTH which is normally at 75 feet? Or will it go up 375 feet from where it is in the gorge before returning to home?
Can I also fly a mission with one of the apps such as DJI's or FPV Camera, Autoflight Logic etc with negative waypoints in the gorge? In other words, I want to take off from the top of the gorge and fly a mission through the gorge at negative altitude such as -100 feet. Will it work?

The RTH return height is set to the height ABOVE the take off position. You only need to set it to clear any obstructions above the height of the take off point. In your scenerio, on selecting RTH the aircraft would climb out of the gorge to the set RTH height or, if higher, to +20m above the take off height turn to face the HP, climb to the RTH return height and then return home. When the aircraft is in the gorge below the take off height the displayed height will be negative.

The RTH height is set via the DJI GO App but it's stored in the aircraft. Therefore it should work with any other apps that use DJI's SDK. However don't quote me on that if it does not work. Also remember to set an appropriate Failsafe RTH mode (hover, land (not advised) or RTH) in case you lose signal between the RC and the aircraft while in the gorge. There is a recent report of someone flying behind peak with the wrong RTH height set. He crashed.