GNSS Precise Point Positioning

Precise point positioning (PPP) is a modeling and processing method that uses global navigation satellite system (GNSS) pseudorange and carrier-phase observations, along with precise satellite orbit and clock products, for single-receiver static or kinematic positioning with centimeter precision. As such it offers an attractive alternative to differential GNSS positioning' making it particularly suited for areas that lack dense GNSS network infrastructure. This chapter describes the PPP concept and provides a systematic treatment of the required models and its different mechanizations. Although PPP was originally conceived as an ionosphere-free dual-frequency technique, single- and multi-frequency PPP are also presented. As PPP relies on accurate satellite position and clock data, we discuss the availability of these products and describe the different orbit and clock products that are available for post-processed and real-time PPP. With the ongoing proliferation of navigation satellite systems, the availability of more satellites and signals brings a range of improvements for PPP. We discuss multi-frequency, multi-GNSS PPP and also develop the models for ambiguity-resolved PPP as a means for reducing the relatively long PPP convergence times. With multi-GNSS PPP, new challenges are also introduced. We describe the need for modeling the inter-system biases (ISBs) and show how they can be corrected so as to realize the tightest possible multiple systems integration. Finally, although PPP has been devised for precise positioning, we also discuss its application for water vapor estimation, ionospheric estimation' and time transfer.