TABLE OF CONTENTS Ronald J. Cosentino
Consultant
David W. Diggle and Maarten Uijt de Haag
Ohio University
Christopher J. Hegarty
The MITRE Corporation
Dennis Milbert
NOAA (retired)
Jim Nagle
ICAO
As discussed in Chapter 7, a single-frequency SPS GPS user can often attain better than 10m, 95% positioning and 20-ns, 95% timing accuracy worldwide. There are many applications, however, that demand levels of accuracy, integrity, availability, and continuity beyond even what a GPS PPS receiver can deliver. For such applications, augmentation is required. There are two general classes of augmentation: differential GPS (DGPS) and external sensors/systems. This chapter introduces DGPS. Chapter 9 will discuss various external sensors/systems and their integration with GPS.
DGPS is a method to improve the positioning or timing performance of GPS using one or more reference stations at known locations, each equipped with at least one GPS receiver. The reference station(s) provides information to the end user via a data link that may include:
Corrections to the raw end user s pseudorange measurements, corrections to GPS satellite-provided clock and ephemeris data, or data to replace the broadcast clock and ephemeris information;
Raw reference station measurements (e.g., pseudorange and carrier phase);
Integrity data (e.g., use or don t use indications for each visible satellite, or statistical indicators of the accuracy of provided corrections);
Auxiliary data including the location, health, and meteorological data of the reference station(s).
Many types of data links may be used, such as radio links at frequencies ranging from low frequencies below...
