Georeferencing inaccuracies on large RTK + GCP datasets

[lupionpe]

On large survey areas, I can get very good GCP error numbers while still seeing a visible mismatch in the final real-world outputs (orthophoto / point cloud) relative to reality.

In my case, I tested on two different areas, both captured with RTK on a DJI Mavic 3E, each roughly:

• ~1,600,000 m²
• ~2,000 images
• gcp.txt
• geo.txt

Reference discussion: https://community.opendronemap.org/t/gcp-show-very-good-results-but-is-not-what-i-see-in-reality/25541

[pierotofy]

Yes that's an outstanding issue with large areas, the entire pipeline needs to keep coordinates in topocentric coordinates until you're ready to export the outputs. Second part of the problem, ODX always outputs in UTM, which introduces shift over large areas, so for accurate results one must use other coordinates system (the same ones as the GCPs)

[lupionpe]

Yes that's an outstanding issue with large areas, the entire pipeline needs to keep coordinates in topocentric coordinates until you're ready to export the outputs. Second part of the problem, ODX always outputs in UTM, which introduces shift over large areas, so for accurate results one must use other coordinates system (the same ones as the GCPs)

Would you say that the changes initially proposed/developed by Yan is a good solution/start point, or should this be handled from another perspective?

[pierotofy]

Yann's changes work correctly for OpenSfM. But they don't help with ODX.

[lupionpe]

Okay, but just for the curiosity, this is the base for the fix in ODX or we could keep using a not-fixed OpenSfM and only ally the fixes direct in ODX?