Effects of satellite selection in GPS position results

In today´s navigation systems, Global Positioning System (GPS) receivers are widely used, either stand alone or integrated with other systems. A GPS receiver finds its position by calculating its distance from satellites whose positions are known. In this structure, the satellites, seen by the GPS receiver, may change in time and this can affect the output of the GPS filter. We analyze, analytically and geometrically, the effects of using fixed and different satellites. We show that using different satellites to determine receiver position lowers the covariance of the position states and geometrically converges to the best possible position estimate. Effects of satellite selection in position estimates are also verified with real data from a road test.