Reading elevation and RTH

[FastHampster]

Hi Everyone, my question is if are say in a middle of a hill at launch and you fly down hill i see the evaluatin setting starting to go in the negative. How can you tell what is the correct height from the ground. If the air craft was to be in RTH mode would it go from height at take off plus the feet that is set or would it take the negative height and add the feet on top so if RTH was at 50 feet and i was negative 10 feet would RTH Be only 40 feet high then?

 

[Kilrah]

RTH height is always expressed as above takeoff point.

 

[msinger]

How can you tell what is the correct height from the ground

You can't since the aircraft doesn't know where the ground is located. If it's close enough to the ground, the downward sensors will detect the ground and that distance will be displayed at the bottom of DJI GO (as shown below).

If the air craft was to be in RTH mode would it go from height at take off plus the feet that is set or would it take the negative height and add the feet on top so if RTH was at 50 feet and i was negative 10 feet would RTH Be only 40 feet high then?

When RTH is initiated, the aircraft would climb to 0 feet and then up to the set RTH altitude. When the altitude displayed at the bottom of DJI GO matches the RTH altitude, the aircraft will then start flying back to the home point.

Using your example, the aircraft would climb to 0 feet and then climb another 50 feet.

 

[FastHampster]

ok so i should have asked this in the orginal post. If RTH will climb to zero then add the 50 feet. What happens when you go up the hill and the evaluation is now higher then the take off point. Will it add 50 on top of the current height or would it subtract it off? Thanks for the replies.

 

[msinger]

What happens when you go up the hill and the evaluation is now higher then the take off point.

If the aircraft is higher than the set RTH altitude, it will return home at its current altitude. It will never descend before returning home.

 

[FastHampster]

ok, just to make sure i understand. If i go up a hill for example and that hill elevation is 50 ft higher then the starting point and the trees are additional 20 feet totaling 70 feet. If the RTH is set for 50 feet it sounds like it will fly directly into the trees then. Is this correct?

 

[Meta4]

ok, just to make sure i understand. If i go up a hill for example and that hill elevation is 50 ft higher then the starting point and the trees are additional 20 feet totaling 70 feet. If the RTH is set for 50 feet it sounds like it will fly directly into the trees then. Is this correct?

RTH and all other heights are relative to your launch point.
You must set an appropriate RTH height to clear any obstacles in the area you are flying.
Look at your trees and estimate how much higher they are than your launch point.
Add a safety margin.
That's what you need to do to set your RTH height.

 

[msinger]

If i go up a hill for example and that hill elevation is 50 ft higher then the starting point and the trees are additional 20 feet totaling 70 feet. If the RTH is set for 50 feet it sounds like it will fly directly into the trees then. Is this correct?

Yes, your aircraft would fly into the trees since it would be 20 feet below the tree tops.