TABLE OF CONTENTS Rob Conley
Overlook Systems
Ronald Cosentino
Consultant
Christopher J. Hegarty, Elliott D. Kaplan, and Joseph L. Leva
The MITRE Corporation
Maarten Uijt de Haag
Ohio University
Karen Van Dyke
Volpe Center
The accuracy with which a user receiver can determine its position or velocity, or synchronize to GPS system time, depends on a complicated interaction of various factors. In general, GPS accuracy performance depends on the quality of the pseudorange and carrier phase measurements as well as the broadcast navigation data. In addition, the fidelity of the underlying physical model that relates these parameters is relevant. For example, the accuracy to which the satellite clock offsets relative to GPS system time are known to the user, or the accuracy to which satellite-to-user propagation errors are compensated, are important. Relevant errors are induced by the control, space, and user segments.
To analyze the effect of errors on accuracy, a fundamental assumption is usually made that the error sources can be allocated to individual satellite pseudoranges and can be viewed as effectively resulting in an equivalent error in the pseudorange values. The effective accuracy of the pseudorange value is termed the user-equivalent range error (UERE). The UERE for a given satellite is considered to be the (statistical) sum of the contributions from each of the error sources associated with the satellite. Usually, the error components are considered independent, and the composite UERE for a satellite is approximated as a zero mean Gaussian random variable where its variance is determined...
