GPS Orbit and Clock Error Distributions

Abstract

Integrity is one of the most important requirements for civilian aviation. One method of achieving the required integrity for supplemental Global Positioning System (GPS) navigation is the use of Receiver Autonomous Integrity Monitoring (RAIM), and for primary means of navigation, Receiver Autonomous Integrity Monitoring and Exclusion (RAIME). The RAIM(E) algorithm parameters depend on the assumed probability of a satellite fault condition (anomaly) and on the fault-free standard deviation of a normal distribution that over-bounds the actual user range error distribution. In this paper, GPS clock and orbit errors are calculated based on the broadcast ephemeredes and truth data obtained from online sources for the three year period starting in June 2005. Anomalous satellite behavior is identified and removed from the data set. The remaining fault-free data are analyzed statistically. A table of anomalies, cumulative distributions, and normal distribution standard deviation overbounds are provided by satellite Block Type.