Slightly relax CR azimuth tolerance and allow Doppler extrapolation #162
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
nemo794
reviewed
Oct 20, 2025
This was referenced Oct 20, 2025
nemo794
approved these changes
Oct 29, 2025
Contributor
nemo794
left a comment
nemo794
left a comment
There was a problem hiding this comment.
Code LGTM. Thanks for testing it, too!
Tyler-g-hudson
pushed a commit
that referenced
this pull request
Oct 31, 2025
…162) * Slightly relax CR azimuth tolerance and allow Doppler extrapolation * fix typo Co-authored-by: SamNemo <11642807+nemo794@users.noreply.github.com> --------- Co-authored-by: SamNemo <11642807+nemo794@users.noreply.github.com>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
I was wondering why the QA PTA results seemed short a few CRs, and the abscal results often seemed to fail. Part of the answer is that we limit the analysis to CRs where the azimuth offset between the LOS vector and CR boresight vector is less than 20 degrees. This is generally a good idea, but several NISAR CRs are oriented roughtly North/South in order to increase compatibility with right-looking sensors and were getting filtered out. I think it's reasonable to extend the default range slightly given that the face is illuminated over ±45° and the geometric optics (GO) model we use is still valid beyond ±20° off-boresight. Here's a plot from Corona et al (DOI 10.1109/MELCON.1996.551596)
It'd be nice to make the tolerance configurable in all the workflows, but that can come later. It'd also be nice to report the angular offset from boresight in the QA products so that we can use that to filter results in a higher level analysis, but again we can add that later.
The other issue I found is that the abscal tool uses the Doppler LUT to find the LOS at the imaging time. This requires an iterative search, and the initial time bracket defaults to the start/end time of the LUT, which corresponds to start/end time of the observation. The problem is that the slant range at the start/end time may fall outside the LUT, causing the calculation to fail. This is easily fixed by allowing the solver to extrapolate when evaluating the Doppler LUT.