this is more a question about sentinel-3 SLSTR data as such than about the toolbox (I haven’t used that yet. So far, I just downloaded netcdf data from EUMETSAT’s coda and played around with it in python). Nevertheless, I thought, this might be the best place to get an answer…
I am trying to compare data over a specific region over time (ie derive some kind of (mini-) time series). to keep things least complicated, I chose two scenes with identical relative orbit and frame numbers and from successive orbit cycles, and i am limiting it to infrared nadir data (ie the *_in.nc files).
comparing the associated elevation data (from geodetic_in.nc) pixel-by-pixel, I realised larger differences than I expected - ok, might happen for 1km-x-1km pixels in mountainous regions.
to be on the safe side, I started checking the lat/lon as well as the cartesian coordinate data.
pixel-by-pixel comparison of lat/lon data looked not perfect, but ok (my quick&dirty single-point geofit yielded a one pixel shift).
however, doing the same for cartesian coordinates showed pixel-by-pixel location differences of around 16km, mostly due to systematic(!) differences in the y-coordinate (the x-coordinate had extremes of about +/-1.7km). For safety, I checked the latitude corrdinates once again (as the ones that should correspond to the y-coordinates. in my understanding of geocoordinates at least.), and they show by no means similarly big differences between the two scenes.
So, I wonder what is going on. whether I just make one or several mistakes in thinking here. or whether there are some issues with the data.
Thanks for any hints!
ps. the two datasets I have used in the above are