I want to conduct an analysis on satellite imagery from the Sentinel-2 mission using Google Earth Engine, and after some research I made, I saw that the data always have to be scaled first before making any calculations, according to the scale-factor mentioned in the Collection's metadata.
This is a bit strange, as a lot of tutorials on the internet are not applying any pre-processing on the imagery before using them.
For example, I followed this tutorial, to create a composite at my area of interest, and then calculate the NDVI values, using the Landsat 7 & 8 Surface Reflectance collections.
Does that mean that my NDVI values might not be correctly calculated? Or because NDVI is an index, therefore a fraction of the NIR and RED bands, is still calculated correctly even with the unscaled values?
Even if that is the case, should I always scale by data before applying any type of analysis?