Finding GCP Pixel Locations

[Tricia Nelsen]

Hello -

I'm trying to add GCP's to my ASP process, however, I'm having a really difficult time determining the pixel locations of the GCPs in the image. I can't use the stereo_gui because I'm using a remote supercomputer to run ASP and just have access to the bash shell. 

Does anyone have a simple way of determining pixel location from lat/long coordinates? I've been messing around with GDAL, but I'm using Digital Globe images, which seem to have a GCP projection relationship rather than a geotransform, but because of that gdallocationinfo isn't returning anything. I know this isn't exactly within ASP, but I figure there must be someone in this group who uses a method to get their .gcp file made.

Thanks,

Tricia

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

In order to find the pixel location from GCP you need to be able to trace a ray from the ground to the camera and see where it intersects your image. That GDAL can't do, as it does not know anything about how the Digital Globe camera works. 

On the supercomputer if a GUI is needed I usually start vncserver (if yours has it) and then connect to it with vncviewer (via port ssh forwarding). Or, you can copy your images back from the supercomputer where you have a GUI, do the work there, and copy things back (but DG images are so huge). Maybe you can just make a little DEM crop, mapproject the DG image onto that crop, and copy the resulting little orthoimage over locally with rsync, then for each pixel you will have a lon-lat.

Overall, using GCP is not a sustainable way of using the ASP tools on the large scale, as it requires too much user interaction. It may be preferable to run bundle_adjust and stereo without GCP, then align the obtained DEM to a reference DEM with pc_align. That alignment transform can be then applied to the cameras too (https://stereopipeline.readthedocs.io/en/latest/tools/pc_align.html#applying-the-pc-align-transform-to-cameras).

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From: ames-stereo-pi...@googlegroups.com <ames-stereo-pi...@googlegroups.com> on behalf of Tricia Nelsen <tene...@gmail.com>
Sent: Monday, March 21, 2022 11:04 PM
To: Ames Stereo Pipeline Support <ames-stereo-pi...@googlegroups.com>
Subject: [EXTERNAL] Finding GCP Pixel Locations

 

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[Tricia Nelsen]

Well I'm glad I can at least give up on GDAL. Thanks Oleg, as always, for your fast and helpful response!

Tricia