How do GPS accuracy and integrity compare to that of existing ground-based navigation systems such as VOR/DME?
A. The basic GPS signal is accurate on a worst-case basis to within approximately 100 meters lateral and 140 meters vertical everywhere on earth. GPS, as provided to civil users, appears to be just as accurate as the most accurate service being provided by the VOR/DME, i.e., non-precision approaches. It should be noted that VOR accuracy degrades as you move farther away from the navigation aid. GPS accuracy is space-based, and thus not constrained by ground equipment. The basic GPS signal is not as accurate as the existing ILSs; however, augmented by WAAS and LAAS, GPS will be able to supply a precision approach capability (CAT-I with WAAS and progressing to CAT-II/III with LAAS).
A. The basic GPS signal is accurate on a worst-case basis to within approximately 100 meters lateral and 140 meters vertical everywhere on earth. GPS, as provided to civil users, appears to be just as accurate as the most accurate service being provided by the VOR/DME, i.e., non-precision approaches. It should be noted that VOR accuracy degrades as you move farther away from the navigation aid. GPS accuracy is space-based, and thus not constrained by ground equipment. The basic GPS signal is not as accurate as the existing ILSs; however, augmented by WAAS and GBAS, GPS will be able to supply a precision approach capability (CAT-I with WAAS and progressing to CAT-II/III with GBAS).
