(RSLC) GeolocationGrid EPSG + coordinate units inconsistency between RSLC HDF5 and other L1 products
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Assessment
- Difficulty
- 5/5
- Estimated time
- Over a week
- Newbie friendliness
- 35/100
- Issue type
- Bug
- Clarity
- Needs clarification
- Activity status
- Quiet
- Tech stack
- xml
- Domain
- data
Research direction
Start by comparing the RSLC geolocationGrid paths with the RIFG, ROFF, and RUNW products and the XML schema using the listed test granules. The team must first decide whether RSLC coordinates should be projected meters or geographic degrees. Done means the chosen representation is consistent with the schema and QA validation no longer reports unit mismatches.
Written by the indexing model from the issue text.
Description
Location:
- RSLC:
/science/LSAR/RSLC/metadata/geolocationGrid/coordinateXandcoordinateY - Comparison products: RIFG, ROFF, RUNW geolocationGrid
Description: RSLC uses geographic coordinates (degrees) in its geolocationGrid while other L1 products (RIFG, ROFF, RUNW) use projected coordinates (meters). The XML schema expects meters for all products, including RSLC.
Test Granules:
- RSLC:
NISAR_L1_PR_RSLC_001_149_D_080_2005_QPDH_A_20251003T130952_20251003T131016_X05016_N_P_J_001.h5 - RIFG:
NISAR_L1_PR_RIFG_013_118_A_171_014_2000_SH_20260222T102514_20260222T102520_20260306T102515_20260306T102521_X05016_P_P_J_001.h5 - ROFF:
NISAR_L1_PR_ROFF_007_106_A_140_008_7700_SH_20251211T140849_20251211T140926_20251223T140850_20251223T140926_X05016_N_P_J_001.h5 - RUNW:
NISAR_L1_PR_RUNW_007_106_A_140_008_7700_SH_20251211T140849_20251211T140926_20251223T140850_20251223T140926_X05016_N_P_J_001.h5
Comparison (sample values from middle of geolocationGrid):
| Product | EPSG | coordinateX units | coordinateY units | Sample coordinateX | Sample coordinateY | Coordinate System |
|---|---|---|---|---|---|---|
| RSLC | 4326 | degree_east |
degree_north |
79.7285468391 | 17.4639440821 | WGS 84 (Geographic) |
| RIFG | 32719 | meters |
meters |
616799.2062 | 8479808.1154 | WGS 84 / UTM zone 19S |
| ROFF | 3031 | meters |
meters |
-1518632.3973 | -424948.7044 | WGS 84 / Antarctic Polar Stereographic |
| RUNW | 3031 | meters |
meters |
-1518632.3973 | -424948.7044 | WGS 84 / Antarctic Polar Stereographic |
Internal Consistency Check:
- ✓ RSLC is internally consistent: degree units + degree values (lat/lon)
- ✓ RIFG/ROFF/RUNW are internally consistent: meter units + meter values (projected)
- ✗ Cross-product consistency: RSLC differs from other L1 products
- ✗ Schema compliance: RSLC doesn't match XML schema (expects meters)
From QA Log:
Differing `units` attributes detected for datasets. XML: 'meters', HDF5: 'degree_east': Dataset /science/LSAR/RSLC/metadata/geolocationGrid/coordinateX
Differing `units` attributes detected for datasets. XML: 'meters', HDF5: 'degree_north': Dataset /science/LSAR/RSLC/metadata/geolocationGrid/coordinateY
Impact:
- Current state: RSLC fails schema validation, but data is internally consistent
- User impact: Tools expecting meters (per the Product Specs Documents) will misinterpret RSLC coordinates
Key Decision:
This requires a design decision from the NISAR team:
- Option A (preferred for consistency): Update RSLC to use projected coordinates (meters) in geolocationGrid, matching other L1 products and the schema
- Option B: Update RSLC XML schema to allow geographic coordinates for RSLC, and accept the L1 product inconsistency
cc: @hfattahi @bhawkins
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- Merged PRs (30d)
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