Misalignment when loading SNAP-exported OCLI GeoTiff into GIS


I have exported a Sentinel-3 OCLI RGB view as GeoTiff using ‘export view as image’ as described in this EUMETSAT tutorial (also featured on the STEP tutorial page). When I open it in ArcGIS and add a basemap layer, the basemap and OCLI image do not align.

I wonder, what I’m doing wrong or whether there are issues with the georeferencing coming with the GeoTiff. Is plainly exporting as GeoTiff maybe not enough, and I first need to reproject as suggested in that topic?

I’m quite an ArcGIS newbie (and my georeferencing/geodatum/projection knowledge is fairly rusty as well), so I admit that my mistake might as well be there. So far, I had the impression though, that if data comes with proper georeference info, ArcGIS takes care of it and adjusts projection and presentation accordingly on the fly. And I can indeed change the projection and the presentation of both image and basemap is adapted. Just, the misalignment remains.

Anyone with some hints or suggestions?

Ok, things look much better when reprojecting the S3-OLCI data to ‘Geographical Lat/Lon (WGS84)’:

I still do not really understand, though, what is going on, why the original does not fit. Particularly confusing that both, original and reprojected dataset, have the same spatial reference attached to it according to ArcMap (left is the reprojected (sub)set, right the original direct geotiff export) :