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Author Topic: Z error precison on roof - Drone Photogrammetry  (Read 1442 times)

fabioHKD

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Z error precison on roof - Drone Photogrammetry
« on: July 16, 2021, 09:37:31 AM »
Hello,

I have a problem with a drone photogrammetry project.

As you can see in the picture, by comparing my point cloud exported from agisoft and an official Lidar point cloud from my country, I have a strange problem of precision in Altitude Z only on the top of the roofs of the houses. At the level of the road and the paths the 2 clouds overlap well (+ -2 cm) IN XY it's ok, but at the roof level there is sometimes 40 cm offset in Z. I've first think of a problem of GCP but I think that the problem does not come from there, I made several tests with 10 GCP, 5 GCP by removing the less precise GCP with a maximum error of 2cm in XYZ

i've do the following workflow :
Import photo
Convert photos to the correct coordinate system
Photo alignment
Import target
Pick target
Updated Transformation
Optimized cameras
Relaunch an Alignment

Where can this problem come from?

The photos are taken with a Mavic pro 2, and dji gs pro double grid oblique 70 °, only part of the photos at the top left were taken manually because no fly zone while trying to respect the same angle of photos.

thank you in advance