Availability, accuracy, reliability, and carrier-phase ambiguity resolution with Galileo and GPS

Abstract

The positioning performance of the Galileo Global Navigation Satellite System (GNSS) operating in conjunction with the Global Positioning System (GPS) is assessed through simulation. Results of two simulations are presented. First, the positioning accuracy and statistical reliability of the systems is assessed using global constellation geometry simulations. Using GPS and Galileo together is shown to improve availability and accuracy. Statistical reliability, meaning the ability of the system to identify and control measurement blunders, is greatly increased due to the much larger number of redundant observations provided by using the two GNSS systems together. Results of a second simulation are presented demonstrating the advantages of using the two systems together for precise carrier phase differential positioning. Modernized GPS and Galileo pseudorange and carrier phase observations are simulated. A new carrier phase positioning algorithm is shown that uses three frequency carrier phase ambiguity resolution in conjunction with stochastic ionospheric modeling. The use of multiple carriers implies more redundancy as well as better observability for ionospheric estimation. This results in a more consistent estimation process and allows for very rapid and reliable ambiguity resolution over much longer baselines than are possible with the current GPS signals. Results of this simulation are presented in the ambiguity resolution domain and the position domain.