Query Regarding Sentinel-1 GRD Image Processing and Data Type Conversion

[omjain26 (Om Jain)]

Hi,

As part of my project, I’m looking to download Sentinel-1 GRD images from the Sentinel-S1-L1C S3 bucket. However, I have encountered alignment issues with Sentinel-2 images, prompting me to download these images from Google Earth Engine instead. The default data type of the images in Google Earth Engine is float64, but I require them in uint16 format to reduce file size.

Despite my efforts to rescale the float64 images, we have been unable to achieve pixel values that match those of the ESA’s uint16 images, even though the spatial alignment is correct. This discrepancy is a significant bottleneck in my workflow, and resolving it is critical for the progression of my project.

To address this issue, I have several queries:

1. Could anyone provide details on how ESA processes Sentinel-1 GRD images post-capture?
2. What method does ESA use to convert these images from float64 to uint16 data type?
3. Do the backscatter coefficients (alpha0, beta0, and gamma0) play a role in this conversion process?
4. Does anyone have any alternative solutions or recommendations for converting the image from float64 to uint16 data type while preserving pixel value integrity?

I would greatly appreciate your guidance on these questions to help us overcome this challenge.

Thank you very much for your time and assistance.

[william.ray]

You can read more into the Sentinel-1 mission here. I would recommend reaching out to ESA directly to answer your questions. You could do this on the STEP-Forum for instance.