bundle_adjustment does not work well

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l pp

Jul 12, 2022, 5:02:43 AMJul 12
to Ames Stereo Pipeline Support
I am trying to generate a high quality DEM using the Resource 3 satellite image. As suggested in the book, I tried to use Bundle Adjustment first, then parallel_STEREO, and finally generate DEM. However, I found that the result of using bundle adjustment was worse than that of not using bundle adjustment. I don't know why.The ASP version is 3.1.1-alpha

1、bundle_adjust -t rpc zy3-BWD.tiff zy3-FWD.tiff zy3-BWD.xml zy3-FWD.xml -o run_ba/run
2、parallel_stereo -t rpc --alignment-method local_epipolar --stereo-algorithm asp_mgm  
--subpixel-mode 2 --corr-memory-limit-mb 2048 zy3-BWD.tiff zy3-FWD.tiff 
zy3-BWD.xml zy3-FWD.xml run_adjust/run --bundle-adjust-prefix run_ba/run
3、point2dem run-PC.tif -o run_adjust/run --search-radius-factor 5 --dem-hole-fill-len 500 
--nodata-value -9999
DEM results:

Alexandrov, Oleg (ARC-TI)[KBR Wyle Services, LLC]

Jul 12, 2022, 12:21:04 PMJul 12
to l pp, Ames Stereo Pipeline Support
Did you change anything except using or not using the "--bundle-adjust-prefix" option? So, except using or not using bundle-adjusted cameras? 

I will suggest running point2dem --errorimage on both point clouds, with and without bundle adjustment, then inspecting the obtained intersection error image. One can use gdalinfo -stats to see their stats, then colorize it with colormap with the same --min and --max values in both cases, then open that in stereo_gui to see how much difference the bundle adjustment makes. It is meant to reduce the intersection error. 

You can also try "--alignment-method affineepipolar".  Then you can try creating a lower-resolution DEM, mapprojecting onto it, and redoing stereo (if you use --bundle-adjust-prefix, then it either be used at all stages or not at all). There are more details here: https://stereopipeline.readthedocs.io/en/latest/next_steps.html#mapproj-example

Hopefully some of these will help with those blunders.  Especially mapprojection is strongly suggested for steep terrains like what you have.

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l pp

Jul 12, 2022, 10:25:41 PMJul 12
to Ames Stereo Pipeline Support

Thank you for your advice. I will try what you suggested

l pp

Jul 19, 2022, 8:29:23 AMJul 19
to Ames Stereo Pipeline Support
Thanks for your suggestion.
After trying to generate a low-resolution DEM first, then use mapproject, and then do stereo, the holes in the DEM disappeared. 
But I found that the resolution of DEM is relatively low and the border is blurred, so may I ask you another question, is there any suggestion to improve the resolution of DEM?

Oleg Alexandrov

Jul 19, 2022, 12:09:30 PMJul 19
to l pp, Ames Stereo Pipeline Support
Our best algorithm is MGM, to be invoked as: parallel_stereo --stereo-algorithm mgm. 

I hope you mapprojected the left and right image at the same resolution, that can make a difference. And one should be careful with what that resolution is. That is discussed here. https://stereopipeline.readthedocs.io/en/latest/next_steps.html#resolution-of-mapprojection

You can also try to hillshade the DEM from stereo_gui, it will be easier to inspect that way. 

l pp

Jul 20, 2022, 2:41:28 AMJul 20
to Ames Stereo Pipeline Support
Thank you for your quick reply .
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