Drone height above crop?

[MNBVCXZ]

Can a drone be set up to fly at a certain height above a crop on undulating ground? Or is it just height above sea level.
Apologies as this has probably been covered before.

 

[radu]

If you're thinking of comercial drones then most likely no.

 

[Dman2]

If your using a DJI then I think the Litchi app lets you set hight above ground to follow contours

 

[Northern farmer]

What sort of height are we expecting? Vertical accuracy from a standalone GNSS receiver is quite poor, cannot expect anything of the order of a few metres above crop.

A friend of mine works in a company that builds drones that fly inside a (big) factory. They have proximity sensors and could certainly follow the field surface. I don't know how fast they can fly, how quickly can a drone adjust height when needed?

 

[A1an]

I'm pretty sure the mavic pro has the ability to do this.

 

[Dman2]

 

[Northern farmer]

It was not clear to me from the video what happens between waypoints. Is it a linear interpolation of the altitude defined for the two waypoints?

Sounds like one would need to define a lot of waypoints to cover a highly undulating field.

Would have been nice to know what is the lowest safe altitude setting. The suggested 10 m margin only for google altitude data inaccuracy sounds high. Or is it actually low, trees could be easily 20 m and the drone might fly a bit off the field and over trees?

 

[Dman2]

That was the first video I came across, loads out there on what Litchi can do

 

[MNBVCXZ]

Thanks for all the replies, much appreciated.

 

[foxbox]

The Mavic Air has obstacle avoidance cameras on the front, rear and bottom; it's reasonably good at avoiding flying in to stuff but I've not dared take on a tree or similar yet. The downwards facing pair of cameras is used to create an image of the take off point (to help it return to it later) and also to create an internal map of some sort, again to help return the drone if it loses GPS or something. There are also infra-red sensors underneath which are somehow used to help orientate the drone to avoid crashing; I'm guessing that between them these features would be capable of terrain following at a relatively low altitude but how they'd get on at 100 feet or so I don't know.

Using the return to home function gives a good idea of how accurate these sensors can be over a solid surface; it'll bring the drone back to a hover 50cm above the exact point it took off from which is presumably beyond the internal GPS ability alone. Whether it could do that as accurately over a standing crop of wheat I don't know. The Mavic Air is still a consumer drone but if the spec has reached a sub-£1k price point it would be reasonable to assume that this kind of thing will be developed a lot more in the coming years for the higher spec stuff.