support smile correction

[zxdawn]

• Issue Apply smile effect correction #5

Here's the array of L1_obj.meta.swir.smile:

I see enpt just saves the delta into smile instead of correcting wvl_center. If we want to correct the wvl_center, we need to duplicate it into 2d array and it will affect something else.

Should we just keep the delta array in the smile variable?

[zxdawn]

Any updates on this PR? @danschef I'm trying to add the EnMAP L1B reader to satpy (pytroll/satpy#2590). If this can be merged, that would be nice.

[danschef]

Well, the changes in this PR just make the L1B reader read the smile coefficients from the METADATA.XML. This is indeed not yet implemented. However, the issue is that the actual correction of the smile is at the moment not implemented at all, see https://git.gfz-potsdam.de/EnMAP/GFZ_Tools_EnMAP_BOX/EnPT/-/issues/35 and https://git.gfz-potsdam.de/EnMAP/GFZ_Tools_EnMAP_BOX/EnPT/-/issues/46. So yes, I can merge the changes, but this only affects the image metadata, it does not mean that the smile is corrected then.

However, please note that the smile effect for EnMAP is actually negligible. The spectral quality without smile correction is already within the requirements, so there is actually no need to implement it.

[zxdawn]

Thanks, I see the smile effects are within 0.5 nm which is negligible. If it's useful to embed this info in the product, then please feel free to merge ;)