`  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    `