Terrain follow

Agriculture General Ag Questions/Troubleshooting
1

Hi, using a DJI M3M to map paddocks. What is the best way to get accurate and consistent altitude in hilly areas?

I found AGL terrain follow inconsistent, I assume the drone is using sensors to estimate its altitude with this? DSM would be an actual terrain map for the drone to follow?
Correct me if I’m wrong here.
Thanks.

2

Yes that is correct. AGL is using the drones sensors and I also found it to be not as accurate for some missions.

Your best option is to use a dsm:

To import a DSM in DJI Pilot 2:

  1. Download from the Internet: Within the app, enable Terrain Follow, select DSM Follow, and choose to download DSM data for your area. Note that the resolution of these DSMs may be around 30 meters, which might not be sufficient for detailed mapping.

Heliguy

  1. Import Your Own DSM: Prepare a high-resolution DSM in TIFF format, ensuring it’s in the WGS84 coordinate system. Transfer the file to the appropriate directory on your remote controller (e.g., DJI/DSM/YourDSMName/), and then select it within the app during mission planning.

DJI Forum

3

Thanks for the info Julius.
Is it possible to create a DSM on pix4d Fields using the surface model?

4

PIX4Dfields creates a DSM, yes. But its in UTM coordinates and needs to be converted / reprojected to WGS84 according to what I found. Also it will be much to detailed and you would need to resample it to a coarser resolution of lets say 1x1 meter. This could be achieved with QGIS, but I have no practcial experience yet.

5

If using AGL real time terrain follow, is it a problem if the height Varys from say 90m to 100m and down to 80m at times?
If a map is still stitched together in pix4d is that reassurance to say it’s acceptable?

6

Its not a problem, terrain following will improve the quality of the map as each image will roughly have the same ground samplingh distance.