isce-framework / isce-framework/s1-reader

Some burst border is larger than the actual coverage

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bug needs triage
Dominant language
Python
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Description

Checked for duplicates

Yes - I've already checked

Describe the bug

During the ANX testing, it was found that some bursts' border attribute has polygons protruding outside the area of the bounding box defined in burst DB. After investigation, I suspect some incorrect latitude / longitude values in geolocationGridPointList, from which Sentinel1BurstSlc.border is computed.
Below is the example data with issue.

SAFE: S1A_IW_SLC__1SDV_20200101T171339_20200101T171405_030610_0381C6_5514.zip
ORBIT: S1A_OPER_AUX_POEORB_OPOD_20210316T161714_V20191231T225942_20200102T005942.EOF
Burst ID: t088_186933_iw2. This is the 9th burst in the IW2 subswath in VV polarization.
Polarization: VV

Below is the plot of each burst borders in IW2 VV polarization. x / y values in the plot are longitude / latitude respectively. The burst mentioned above is labeled as 9 / 9, meaning that it is the 9th burst In the subswath.
Screenshot 2023-07-22 at 01 47 33

Below is how the 9th border looks like when it is reprojected and overlaid on the corresponding bounding box. The red polygon is the burst border, and the blue one is the bounding box from burst DB.
Screenshot 2023-07-21 at 18 48 08

Below is how the screenshot of the RTC product (VV pol.) suggesting that the coverage of the actual burst is well within the bounding box in burst DB.
Screenshot 2023-07-22 at 02 12 37

What did you expect?

I think we need an algorithm to take care of the cases when incorrect longitude / latitude information in is in geolocationGridPointList. Also it would be necessary that any downstream workflows that make use of Sentinel1BurstSlc.border needs to be aware of this issue.

Reproducible steps
The test dataset mentioned above is available upon request.
Environment
- Version of this software [e.g. vX.Y.Z]
- Operating System: [e.g. MacOSX with Docker Desktop vX.Y]
...

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with Sentinel1BurstSlc.border and the geolocationGridPointList data described in the issue, using the referenced SAFE, orbit file, and burst ID once the test dataset is available. Compare the computed border with the burst DB bounding box and RTC coverage; done means the handling of incorrect coordinates and downstream use of border are defined and covered by reproducible validation.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
data
Issue type
Bug
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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