From the moment satellites are launched and first sending back data their orbit is decaying and getting closer to mother Earth. This necessitates the constant launching of new satellites and switching of data streams - mucho opportunity for data fiddling & tweaking - On top of this you have variations in wind and currents piling up ocean water here n there in various places at different times - How the data is handled by NASA to take account of all these natural variations - I would not trust without Indie checking
