You get the impression that typical consumer devices can now track twenty or more satellites from different constellations. This gives the possibility of a huge number of calculations. I am not very familiar with the types of error that effect GPS but you would imagine with a large of number of calculations, it would be trivial to filter out certain systematic errors (eg single faulty satellite). More than that, with so many calculations, you would think just taking an average would be entirely satisfactory. 

So for a typical tablet, does SD simply get a single calculated position from the host device or does it have access to individual calculations, and if so does it do any processing to pick the best fix?