Starting a Litchi mission from a tall building

rainsipper · Dec 5, 2020

Hi there, I have been flying Litchi mission from a tall building (about 80m high) and got great results. I checked all my flights using Virtual Mission. Everything looked fine but I found the altitude is not reflecting the actual situation. The whole flight went up about 50m of what I intended. I reviewed the footage and tried to adjust it in Litchi but visualization in Vitual Mission showed part of the path submerged below sea level.

My question is: can I set the absolute altitude instead of relative altitude in Litchi? I checked "above ground" in Litchi and the difference is not significant. I started the waypoint flight at 90(90) but the drone started the mission from 90m above the roof of the building, not 10m above it.

Repaid1 · Dec 5, 2020

Simply set litchi altitude at 10 meters?

rainsipper · Dec 5, 2020

If I set 10 most of the mission will be run under sea level in the simulator which gives me no confidence to commit.

Repaid1 · Dec 5, 2020

Well your AGL is already 80M if you go off the rooftop and then down, it IS going to report negative altitude. Your Altitude isn't in reference to sea level at any time. It is set to "0" reference point at take off No way around that other than to take off from ground and set a way point to 90 meters above the roof and then continue mission from there.

rainsipper · Dec 5, 2020

You are right, thanks. I will try decreasing the altitude bit by bit and see what the results are.

I think this issue is google earth doesn't take the roof of my building into account so I won't be able to get accurate readings.

rainsipper · Dec 7, 2020

I bite the bullet and did some test flights over the weekend. Starting the mission at about 80m above ground, without any elevation reference from Google Earth I did all the maths myself. One flight a little bit more aggressive than the previous one, my Air seemed almost brushing the sea but I knew it's flying at least 15m above sea level.

Thanks for the assistance and I rethought the whole logic of how Litchi worked. I ran a serious mission to have the drone crossed the harbour, filming the skyscraper there. It was a 5000m mission, it was a thrill, my heart couldn't stop pounding but I made it.