Editing Global Positioning System (section)

==== Hypercones ====
The clock in the receiver is usually not of the same quality as the ones in the satellites and will not be accurately synchronized to them. This produces [[pseudorange]]s with large differences compared to the true distances to the satellites. Therefore, in practice, the time difference between the receiver clock and the satellite time is defined as an unknown clock bias ''b''. The equations are then solved simultaneously for the receiver position and the clock bias. The solution space [''x, y, z, b''] can be seen as a four-dimensional [[spacetime]], and signals from at minimum four satellites are needed. In that case each of the equations describes a [[hypercone]] (or spherical cone),<ref>{{cite journal|title=GPS Solutions: Closed Forms, Critical and Special Configurations of P4P | doi=10.1007/PL00012897 | volume=5|issue=3 |journal=GPS Solutions|pages=29–41 | last1 = Grafarend | first1 = Erik W.|year=2002 | bibcode=2002GPSS....5...29G | s2cid=121336108 }}</ref> with the cusp located at the satellite, and the base a sphere around the satellite. The receiver is at the intersection of four or more of such hypercones.