Umbra SAR SIDD processing

[Ryan Rock]

I am trying to run stereo processing on Umbra images but the only images I have available are the ...SIDD.nitf format rather than the GEC.tif images that are used in the ASP example. I have been able to extract the RPC coefficients from the SIDD images. Is there a way to use the .nitf format images and the lists of coefficients with ASP?

[Oleg Alexandrov]

I believe the SIDD images are those that had additional processing and look similar enough to GEC (unlike the more raw SICD images). In that case, our tools should work if you put the RPC coefficients into an .rpb file as GDAL expects. So, if you have a file called image.nitf, you should have a file called image.rpb. See the GDAL doc for a note on .rpb: https://gdal.org/en/stable/drivers/raster/gtiff.html.

You can check that the rpb coefficients are read correctly by doing gdalinfo image.nitf, and see if they get printed. 

We found SAR images to be very hard to process with ASP, especially when they look visually dissimilar. It is suggested to start with very similar images first. One can also reduce them to lower-resolution, to decrease noise and increase similarity, at least for initial processing, with a command such as gdal_translate -r average -outsize 25% 25%.

Apart from the issue of images being correlated well, there is the issue of how good the camera models are. We did not test SICD enough to tell.

Let us know how it goes. This will be tricky to pull off.

[Pratanu Maity]

Hi Ryan,

Could you please provide information about how you have extracted rpc coefficients from Umbra SIDD image ?

Thank You.

Regards,

Pratanu

On Thu, 26 Jun, 2025, 10:23 pm 'Ryan Rock' via Ames Stereo Pipeline Support, <ames-stereo-pi...@googlegroups.com> wrote:

I am trying to run stereo processing on Umbra images but the only images I have available are the ...SIDD.nitf format rather than the GEC.tif images that are used in the ASP example. I have been able to extract the RPC coefficients from the SIDD images. Is there a way to use the .nitf format images and the lists of coefficients with ASP?

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[Ryan Rock]

Thanks for all the info Oleg. I will try to format the RPC coefs into the .rpb file for gdal to read. And thank you for the guidance on slecting images. We have 16 images of our site so I will take some time to make sure I get a suitable pair before proceeding.

Pratanu - I used sarpy to open the nitf file https://sarpy.readthedocs.io/en/latest/io/product/converter.html and then used the sidd_meta to read the metadata. 

[Ryan Rock]

Hi Pratanu - i used sarpy to open the .nitf file and access the metadata using sidd_meta then wrote it out to a csv. 

Oleg - thanks for the info. I will look into putting the coefficients into an .rpb file. Thanks for the guidance on image selection. I have 16 images to choose from for my aoi so I will spend some time making sure I start with a suitable pair.

On Thursday, June 26, 2025 at 11:07:24 AM UTC-6 tryingph...@gmail.com wrote: