Constant AGL mission capability?

[raylo32]

Just curious... this was something the Ardupilot community was working on and wonder if The M2 can do it perhaps with alternative flight software. By "this" I mean conduct a flight/mission where the aircraft would maintain a constant altitude above ground, not relative to the elevation of the home point. IOW it would follow the land contours up and down to maintain a constant AGL and video perspective without user interaction. I know you can include altitude when you program waypoints. But it would be much easier to have a constant AGL mode, especially if that could be used in free flight.

 

[gnirtS]

The downward sensors that produce a height above ground only work below about 20ft or so with any real accuracy so such a mode would be fairly useless.
It can do a terrain follow in one direction (upwards only) using activetrack.

 

[raylo32]

I wasn't thinking about using the sensors... I know those are short range... I was thinking terrain follow using GPS data that includes the ground elevations. The mode would take the GPS elevation data for points under the drone's path and apply the delta as it moves to maintain a selected AGL, that you could change on the fly with throttle input. I am not a dev so I don't know how difficult that would be to program or if that dataset is readily accessible. It would help in some scenarios like flying up (or down) a mountain slope, or a on a mission leg that goes over a couple ridges and valleys.

 

[gnirtS]

The amount of data isnt freely available in the resolution required and certainly not small enough to fit into a drones storage to be used in real time.
It'd also potentially have gaps such as trees, power lines, new structures and so on.

In addition, GPS altitude is significantly less accurate than horizontal so you could have errors in the region of 10s of metres anyway.

 

[53-63-6f-74-74]

Just curious... this was something the Ardupilot community was working on and wonder if The M2 can do it perhaps with alternative flight software. By "this" I mean conduct a flight/mission where the aircraft would maintain a constant altitude above ground, not relative to the elevation of the home point. IOW it would follow the land contours up and down to maintain a constant AGL and video perspective without user interaction. I know you can include altitude when you program waypoints. But it would be much easier to have a constant AGL mode, especially if that could be used in free flight.

Free flight AGL = No. However, waypoint AGL is definitely possible and works very well with Litchi Missions, which can easily be configured to use Google Earth elevation datum, OR if you have some knowledge of the process you may import your own LIDAR-derived DEM (WGS-84 Esri ASCII Grid format) in the Litchi Mission Hub and use that instead of the Google Earth elevations, which would give you a MUCH higher degree of terrain accuracy. The aircraft uses its barometer for elevation and GPS for horizontal positioning. DroneHarmony also has the similar function of importing an elevation model into the app.

 

[gnirtS]

Barometer is always going to give height above takeoff location (ie QFE) which can vary unless an absolutely identical flight route is flown every time (ie using waypoints).

 

[Cdcolt]

Litchi Mission Hub allows you select an AGL height rather than the default height above launch point for Waypoints. Just make sure your waypoints are close enough to compensate for abrupt changes in terrain elevation.

 

[sar104]

Litchi Mission Hub allows you select an AGL height rather than the default height above launch point for Waypoints. Just make sure your waypoints are close enough to compensate for abrupt changes in terrain elevation.

But note that it only sets the altitude at the waypoints, linearly interpolating between them, rather than keeping a continuous altitude AGL. So it is important to have enough waypoints to resolve terrain features, or at least ensure that there are waypoints at the high points in the terrain.

 

[raylo32]

That is exactly how it works in the Tower app, too. But think how easy it would be to plan a mission if all one had to do is specify WP horizontal positions and a set value for AGL and not have to scrutinize topo maps. I guess I am getting lazy in my old age.

But note that it only sets the altitude at the waypoints, linearly interpolating between them, rather than keeping a continuous altitude AGL. So it is important to have enough waypoints to resolve terrain features, or at least ensure that there are waypoints at the high points in the terrain.

 

[sar104]

That is exactly how it works in the Tower app, too. But think how easy it would be to plan a mission if all one had to do is specify WP horizontal positions and a set value for AGL and not have to scrutinize topo maps. I guess I am getting lazy in my old age.

Yes - that would be very nice. It would also not be that hard to implement - it would just require Litchi (or whichever software) to generate a ground elevation profile under the requested flight path and then automatically add enough extra waypoints to resolve the terrain.