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The statement below quoted from ""User-satellite geometry"" seems to be incompatible with the navigation equations.  The time for receiver clocks is synchronized with the satellite clocks as a part of the solution process.  It is certainly true that the receiver location is at the intersection of 3 spheres since it is at the intersection of n spheres where n is greater than 3.
""It is sometimes incorrectly said that the user location is at the intersection of three spheres. While simpler to visualize, this is only the case if the receiver has a clock synchronized with the satellite clocks (i.e., the receiver measures true ranges to the satellites rather than range differences). There are significant performance benefits to the user carrying a clock synchronized with the satellites. Foremost is that only three satellites are needed to compute a position solution. If this were part of the GPS system concept so that all users needed to carry a synchronized clock, then a smaller number of satellites could be deployed. However, the cost and complexity of the user equipment would increase significantly.""  Licensed Professional Engineer    "