Defining pseudoranges as , we see they are biased versions of the true range: .section 4 beginning on page 15 Geoffrey Blewitt: Basics of the GPS Technique Since the equations have four unknowns [x, y, z, b]—the three components of GPS receiver position and the clock bias—signals from at least four satellites are necessary to attempt solving these equations. They can be solved by algebraic or numerical methods. Existence and uniqueness of GPS solutions are discussed by Abell and Chaffee. When n is greater than four, this system is overdetermined and a fitting method must be used.
defining pseudoranges as  we see they are biased versions of the true range section 4 beginning on page 15 geoffrey blewitt basics of the gps technique since the equations have four unknowns [x y z b]—the three components of gps receiver position and the clock bias—signals from at least four satellites are necessary to attempt solving these equations they can be solved by algebraic or numerical methods existence and uniqueness of gps solutions are discussed by abell and chaffee when n is greater than four this system is overdetermined and a fitting method must be used