Data unit of sentinel-1 data downloaded from sentinel hub

Microwave Toolbox
#1

Hi all,

I am new to sentinel-1 data. And I am trying to use images downloaded from EO for further processing, but confused with the data unit. When I download data from the EO browser, the pixel values range from 0-255, and I am wondering if they have any physical meaning?

Thanks a lot!

#2

The data from the EO Browser is rather for visualization. It is not strictly calibrated, but ready to use in a GIS.
If you want calibrated radar backscatter, I recommend using GRD data from the official Sentinel Hub: ESA Copernicus scihub and apply calibration and terrain correction yourself: Proceedings | Free Full-Text | Sentinel-1 GRD Preprocessing Workflow

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#3

Hi ABraun,

Thanks a lot for your reply, I will have a go with the sentinel hub you suggest.

And as you said the data from EO browser is for visual purpose, wondering if there is a known procedure of how the pixel values were produced?

Thanks again for your time.

#4

They are created the same way, but are converted to Integer before the export to reduce the file size.

#5

Thanks for the reply! But in my understanding (sorry I am new to this area), I was expecting the backscatter values to be in a typical value range or something, rather than 0-255 (that looks more like just the brightness of the pixels), would you mind correct me if am wrong?

#6

Absolutely. But the data is rescaled during the export/download. Conversion to another file type always leads to new value ranges.

#7

And the number are not likely to be converted back I guess…Thank you so much for the help :laughing:

#8

This would require precise information on how this stretch was performed. I didn’t find any information in the EO Browser documentation.

So you can either process the data yourself: How to Radiometrically Terrain-Correct (RTC) Sentinel-1 Data Using the ESA Toolbox – ASF
or download analysis ready data from ASF: Webinar: Sentinel-1 On-Demand RTC Processing: Generating Analysis-Ready SAR Data with ASF Vertex | Earthdata

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#9

That created the same way and are converted to Integer before the export it will reduce size of file.

#10

Thanks a lot for the information, that was very helpful!

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