I’m currently conducting research that involves analyzing water indices (NDWI) over several hundred sites in Somaliland using Sentinel-2 data. I’ve encountered an issue where the SentinelHub API consistently returns zero reflectance values for bands B03 and B08 (all bands, really, but those are the ones I’m trying to get…) across all available dates, even though valid imagery is displayed in Sentinel Playground for the same locations and time period.
bbox info:
minx = 44.186379000243164, miny = 9.123248472610312
maxx = 44.188356199485646, maxy = 9.124770047412461
(Coordinates in EPSG:4326)
The bounding box has also been tested with an expanded size (up to 5 km), but the issue persists.
- Tested data collections:
- Sentinel-2 L1C
- Sentinel-2 L2A
- Dates tested:
73 available dates throughout 2023, retrieved successfully usingWebFeatureService
. - Evalscripts tested:
- True-Color (B04, B03, B02)
- Raw B03 and B08 reflectance retrieval
- NDWI calculation
Despite successful API requests and correct bounding box alignment, all pixel values for B03 and B08 reflectance return 0.0, leading to NDWI values of NaN
. The issue is consistent across both Sentinel-2 L1C and L2A collections.
example of output:
[Site_5] Date: 2023-12-28T00:00:00Z, B03 min: 0.0, max: 0.0
[Site_5] Date: 2023-12-28T00:00:00Z, B08 min: 0.0, max: 0.0
- Expanded bounding box tests (5 km around the site) also return zero reflectance values.
Steps I’ve Taken:
- Ensured that the bounding box is correctly projected in EPSG:4326 (WGS84).
- Tested both Sentinel-2 L1C and L2A data collections.
- Expanded the bounding box significantly to capture surrounding pixels.
- Checked the availability of valid data using Sentinel Playground.
- Verified that dates are correctly retrieved via
WebFeatureService
.
I’d appreciate help figuring out:
- Whether SentinelHub’s internal masking or processing logic is discarding valid pixels.
- Whether this issue is specific to the API processing for this region.
- Any suggestions or configurations I can apply to retrieve valid reflectance data through the API.
- Is there a minimum AOI size limit? Some of these sites are quite literally less than a pixel, potentially this might cause issues with the API handling?
Any help is appreciated! Can send in example Python scripts if necessary.