Now here you Siafu go misquoting me again  I did not describe the solution of the navigation equations as the intersection of three spheres  I said I clearly understand that the GPS navigation equations consist of n n greater than  equations for the surfaces of n spheres and that the solution of these n equations consists of a clock bias and a point at the intersection of these n sphere surfaces  This of course implies that the position part of the solution is at an intersection of any three of the n spheres but this is not a description of the solution but instead an implication of the solution      Kendall credentials certainly do matter since if you dont have the proper education then you cant understand the material and are certainly unqualified to write  Also Kendall pride is a virtue  I am very proud that I have received a superior quality of education and that I have had a highly successful engineering career  The fact that I have the great virtue of pride does not mean that I do not treat others with respect and civility      DVdm you start your post with the word Thats  This usage of the word that is very vague and ambiguous in this context  Also you need to say what you are talking about rather than make some reference