Method and apparatus for providing GPS pseudorange correction information over a selected geographic region S with a diameter of up to 3000 km with an associated inaccuracy no greater than 5 cm. N spaced apart GPS fiducial stations (N.gtoreq.3), whose location coordinates (u.sub.n, v.sub.n, v.sub.n)...http://www.google.sh/patents/US5477458?utm_source=gb-gplus-sharePatent US5477458 - Network for carrier phase differential GPS corrections
