bundle_adjustment does not work well

[l pp]

hello,

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

command:

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]]

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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From: ames-stereo-pi...@googlegroups.com <ames-stereo-pi...@googlegroups.com> on behalf of l pp <pplau...@gmail.com>
Sent: Tuesday, July 12, 2022 2:02 AM
To: Ames Stereo Pipeline Support <ames-stereo-pi...@googlegroups.com>
Subject: [EXTERNAL] bundle_adjustment does not work well

 

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[l pp]

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

[l pp]

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]

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. 

To view this discussion on the web visit https://groups.google.com/d/msgid/ames-stereo-pipeline-support/2914acf9-daa8-49ef-a542-99855baddcd9n%40googlegroups.com.

[l pp]

Thank you for your quick reply .