Q: wcs downloads are spatially a bit shifted/squized - compared to browser downloads (this are correctly placed). Is there some mistake in EPSG transformation? Is it possible to work with transformation using sentinelhub-py?
A: Some distortion should be expected anytime reprojection is done. Original data are stored in UTM projection and if you want to avoid any error, you should use this one. What probably happens in your case is that you export in EPSG:4326 (via WCS) and then you look at this in QGIS with EPSG:3857 setting, so reprojection is happening twice, therefore errors are so much more visible.
We are pretty certain that there is no (additional) mistake done in a reprojection, with the exception of normal inaccuracy of the reprojection (as mentioned).
However, we will check once again on this specific example, just to be sure.
If you want to use EPSG:3857 in WCS, this should be easily done. You simply change the
and also pass BBOX parameters in EPSG:3857
(I am not certain, where this is done in sentinelhub-py, but it should not be too difficult).
As mentioned above, if you want to have best quality of the results, you should use UTM projection.
Q: resolution of browser downloads is better (some kind of downscaling is used?) How can I achieve same results with automated download?
A: I am not sure, which setting you have used in EO Browser, but EO Browser is using the same WCS as you are using from sentinelhub-py, so you should be able to get exactly the same results.
If you want to get “better” resolution, set e.g. RESX=5m&RESY=5m&DOWNSCALING=BICUBIC
That being said, be aware that Sentinel-2 data are in 10m resolution (in UTM projection), so any rescaling will produce artificially “better” results.
Q: values with ATMCOR are considerably lower than with NONE, thus more diverse from L2A. I had expected it other way round - L1C corrected to be closer to L2A than non-corrected. Is it wrong assumption or I have mistake in processing chain?
A: When using ATMFILTER=ATMCOR, you are using our “statistical” atmospheric correction (see the FAQ mentioned above), which is not as accurate/detailed as “official” L2A.
Now as the L2A is available globally, we certainly recommend using L2A data source (make sure you do not use any ATMFILTER on L2A data)