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Author Topic: Strange(bad) results: 0.9.0 vs 0.8.5 on 5 sq km project (17 GCP, 221 photos)  (Read 4686 times)

andyroo

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I have a 50M face model with 221 aerial photos covering about 5 sq km with 17 GCPs. Due to issues I encountered with the surface generated from 0.9.0, I downgraded to 0.8.5 and regenerated the project using the same parameters.

General method was: align photos, generate geometry, select control points, optimize, regenerate geometry, export orthoimage, average image, and DSM. Project datum and control points were entered in WGS84. surfaces were exported in NAD83UTM10.

I generated a surface with 50M polygons with each version, using the same base project (photos and alignment). Then I compared them to each other and to a LiDAR flight flown in April. The results were not good for the DSM generated with 0.9.0. Here's what I found:

DSM surface comparison with LiDAR was much better with 0.8.5. Unchanged surfaces were < 0.25 m different on average. With 0.9.0, elevation values on unchanged surfaces were 8 - 20 meters off, and warped into a frown. See first attached image  (sorry - values in U.S. feet).

DSM comparison between 0.8.5 and 0.9.0 showed that there was a warp on 0.9.0 Reason unknown. What I especially don't understand is why the control points looked ok in the project but not the DSM. Possibly export format issues?

Another thing I noticed was the quality of the DSM was worse in 0.9.0 (see second attached image). I've highlighted two features that I noticed - pits, and lines.

I am not sure if the warping issue is because of the UTM10 export, because the project started as a 0.8.5 project, or because of some inherent issue in 0.9.0. But I am pretty sure that the lines and pits are exclusive to 0.9.0.

Andy

andyroo

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Anyone else have any insight on this? I've gone back to 0.8.5 and I was wondering if there is a way to test my next flight with 0.9.0 without having to manually input control points twice.

But if the problem is due to a project being partly done in 0.8.5 then it seems like that's exactly what I'll have to do - make a project with 0.8.5, upgrade to 0.9.0 and create the same project, then compare.

(also if I am posting in the wrong part of the forum I apologize)

Matt

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Yep I am getting the same photo line artifacts but not in all projects.  I get it in areas of very high overlap 10+ photos with insufficient/uneven control. I get funky circles thrown in for free (see picture). Submit a support request and see how you go. Re your next flight just start the project in 8.5 and save a copy for a try in 9.0.