plane fit orthomosaic

[william]

Hi,

I am dealing with UAV imagery. My GPS data is imprecise, so it can't be relied upon to produce an orthomosaic with the correct orientation. For most of my image sets, the point cloud looks great, but the orthomosaic is at the wrong angle and thus unusable.

I want to abandon the georeferenced orthomosaic, and instead do some kind of plane fit on the point cloud (our data is very flat) to determine the correct orthomosaic orientation. Does anyone have any ideas for how this should be done?

I think I will have to export the point cloud, fit it to a plane using other software, then use those plane coefficients. But I appreciate any suggestions.

[Alvaro L]

CloudCompare !!!

[Alexey Pasumansky]

Hello william,

In PhotoScan you can use Planar option in the Build Orthomosaic dialog, providing you have generated mesh model or DEM in the same planar mode.

[william]

Thanks. I don't know why I didn't consider Planar XY before. That does seem to work!

[william]

Just to clarify, does the Planar option do an automatic plane fit, or does it require the user to select 3 plane points? I am looking for an automatic plane fit.

[Alexey Pasumansky]

Hello william,

What do you mean by "automatic fit"? Do you expect PhotoScan to have a kind of weighted average plane, depending on the distribution of the mesh vertices in the space?

[william]

Yes, that's the idea. Or based on the distribution of the points in the point cloud, for instance. Some external libraries offer plane-fitting for point clouds. The normal vector for that plane could then define the orthomosaic orientation.