Smart RTH altitude setting

[Skylane]

You guys were right on. Flew the drone up the mtn to altitude of 666 feet (interesting elevation huh). Drone was only 12 feet AGL for me to take a picture of a target hanging on a cliff face that we shoot at with our precision rifles. Turned it around and hit RTH. Drone maintained 666 feet for a flight of 1000 meters till over home, then initiated descent and landing.

Spotting scope! Awesome!

 

[Xtreme Drone Pilot]

666 feet (interesting elevation huh)

1666 or better yet 6666 are much more satisfying to see on your screen. It tells you, "You're not in DJI jail, hooray!"

 

[msinger]

So, if I understand correctly, to be totally "safe", you should never use smart RTH if the very tops of the highest trees at the top of your site are higher than 500m.

To be totally safe, the RTH Altitude should always be set to the highest obstacle over top of the takeoff point plus about 50 feet to add in some room for error (since the current altitude displayed in DJI GO is just an estimate).

 

[fiberdude]

Case study: the RTH altitude fell a few meters short of clearing the hill-top trees, but fortunately, OA kicked in and Mavic Pro was smart enough to increase altitude by a few meters (even backed off a bit from the tree) until RC regained contact with the AC (see footage here Dropbox - QQ20171220-193053-HD.mp4 )

 

[Thongjy]

I've tested this as well, and it's true: If above the RTH altitude, it will not decend. The only issue I've thought of is if you take off, then ascend to greater than 500m (to the top of a ski area, say), then descend beneath the tree line, if things go awry, you could be in trouble, as the A/C could not ascend any higher to avoid the trees as it heads home. Makes me nervous.

Anyone know how does the Mavic actually know the actual height relative to the home point over different terrain?

 

[msinger]

Anyone know how does the Mavic actually know the actual height relative to the home point over different terrain?

It doesn't know that.

When RTH is initiated, the Mavic will ascend to the RTH altitude if the current altitude displayed in DJI GO is below the RTH altitude.

 

[rfc]

As msinger points out, it doesn't. But you can estimate it if you are familiar with the terrain beneath the Mavic, or if your maps show elevation, which would be subtracted from the Mavic's altitude. It'd sure be nice if the Mavic had a radar altimeter, lol!

 

[davesdronevids]

Sort of in regards to this....I set the app to Imperial MPH but when I set up things like RTH Altitude must it still be in Meters?

 

[msinger]

I set the app to Imperial MPH but when I set up things like RTH Altitude must it still be in Meters?

The RTH Altitude must always be set in meters.