Pointcloud is 300 meters higher than real world

WebODM
#1

I have run 280 pictures on the webodm lightning cloudservice.

The pointcloud is 300 meters higher than real world. The quality report says that lowest point is.460 meters, but in real world the lowest point is 150 meters above sealevel.

I am flying the drone on different elevations since I aml following the terrain. Is this causing the problem ?

The drone used is a DJI Mavic 3.

Can anoyone suggest what I am doing wrong ?

Here is the options I ran:
|Processing Node:|Lightning (manual)|
|Options:|auto-boundary: true, dsm: true, dtm: true|
|Average GSD:|5,57 cm|
|Område:|989 109,3 m²|
|Reconstructed Points:|13 629 859|

Loggfile, Quality report, source photos etc can all be viewed here: Jottacloud

1 Like
#2

You might need to use GCPs to tie the elevation down to reality properly.

Have you checked the reported elevation values in the images coming from your Mavic?

#3

Thanks - you pointed me in the right direction. I took some samples from the drone and it is constantly way to high in the EXIF data. This is a brand new Mavic 3, hopefully it may be fixed with coming firmware updates.

Thanks again.

2 Likes
#4

Maybe! We’ve seen reports from various combinations of sUAS and firmware that the elevation recorded in EXIF is not always consistent (Above MSL, Above GL, Above take-off, etc) or what one would expect…

If you can, a-priori in-situ GCPs will not only greatly improve your Z-axis accuracy, but your X/Y as well. If you have access to the site and can spray field chalk Xs and record their location with a reasonable-quality GPS, you’re golden. Mats, AruCoMarkers, or immobile/immutable easily distinguished features are also good options.

Or if not, you can use something like exiftool to apply a flat offset to try and correct for the elevation offset.