Flying a mission below the starting elevation

I flew a mission last weekend where the only access was at the top of a hill but the mapping was being performed in the valley below. The valley ranged down to about 160 metres below the starting elevation.

In order to fly with a reasonably small (50 or so) images I had to specify a flight elevation of 70 metres but this meant I was actually flying up to 230 metres above the actual ground being surveyed. As a result resolution was limited and the flight totally oversampled the survey area.

What I really wanted to do was fly 70 metres above the survey area not above the takeoff point.

I realise this is problematic but any suggestions would be appreciated.

Ian Grierson April 04, 2016 05:10

Official comment

Sorry we missed this initial question.

This is an interesting issue. To properly address it we would have to add a way to enter the ground elevation of the area being mapped that would act as starting point for the overlap calculations instead of using the takeoff location. For small changes, this wouldn't likely be an issue but for large ones it would likely start running into flight height limitation issues that are limited by the DJI SDK.

It is actually a pretty tricky issue for a lot of reasons (waypoint planning, safety, return-to-home issues and so on). Especially so with flying below the takeoff location...

We do plan on adding terrain awareness which will address this problem so we won't likely be adding any manual adjustments.

In the meantime, the only real workaround is to take of closer to the elevation of the area being surveyed.

Jay April 22, 2016 16:58

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4 comments

This is a very good question. I have the same situation while flying in Hong Kong. I basically always launch from hill side locations and like the above subscriber, often 150 meters + above the mapping area. The problem is exactly that the application currently do not allow for this kind of situation. Manually adjusting the application altitude to say 10 M (which would still be very high with an actual aircraft mapping at 160 meters) is not working because of the application calculating the mapping at 10 M and NOT the actual 160 M.

A reply from the developer would be appreciated, thanks.

Claus Thanner April 22, 2016 05:40 0 votes

Perhapse the first step a simple "offset" for standing on the roof (i.g. 20m) whould be great too...

Alexander Z. April 22, 2016 17:43 0 votes

With the testing of our Terrain Awareness feature we discovered that DJI does not allow for waypoint flight below the takeoff point. No error is given. It just gets there and hovers.

Tudor July 21, 2016 17:44 0 votes