Sentinel-1 CRS related info

  • 26 April 2024
  • 4 replies
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Hey,

This might be a bit of a silly question, but I’m querying Sentinel Hub for Sentinel-1 data over a specific AOI.
Why is it that for Sentinel-1 we have to use a tuple (something like 20,20) for the resolution, and also how does the CRS affect the output?
For instance, for the same AOI, requesting data with EPSG:4326 yields only one pixel, where as using the EPSG:3035 gives me about 17x14 pixels.
Also in general, where do I find which CRS to use for a specific satellite?
Additionally, if I understand correctly with Sentinel 1, this is also dependent on where the AOI is in the world? Correct? I guess in the EU Sentinel-1 offers higher resolution, where as in the rest of the world it offers lesser resolution?
Would appreciate some input about how to wrap my head around the CRS when it comes to Sentinel Hub.


4 replies

Hi,

The reason why the size of the image in pixels changes with CRS will depend on the units of the CRS. For example, EPSG:4326 units are in degrees, whereas EPSG:3035 units are in metres. The resolution you use as your input will be in the native units of your CRS.

Satellite imagery is generally processed in either WGS84 (EPSG:4326) or in UTM zones. The choice of projection depends more on the location in the world that your AOI is in. I would suggest doing some research into how projection systems work. If you google this, you will find numerous free courses that explain the different types.

Sentinel-1 GRD availability is highest in Europe currently, as only one satellite is operating after the failure of Sentinel-1B. But this doesn’t mean there is no coverage in the rest of the world. For more information, please read the associated documentation page. The resolution is constant globally.

Hey, thanks.
The reason I asked is because the documentation is a little tough to navigate for me as a beginner at EO.
Kinda piecing together how to use the API from the examples.

No problem, if you see anywhere where you feel the documentation can be improved, please let us know! We always appreciate feedback.

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