Reliability Analysis of Phase Observations in GPS Baseline Estimation

Abstract

The use of outlier detection, reliability measures from the theory of survey network analysis, and the concept of condition numbers from linear algebra are applied to the statistical and numerical analysis of Global Positioning System (GPS) phase‐difference data in baseline adjustments. Outlier tests are given for the cases of a‐priori and a‐posteriori variance factors. Expressions for internal and external reliability measures are treated for the case in which blunders are assumed to be present in the data. These measures are evaluated for a GPS baseline for the cases of fixed integer and floating point ambiguity unknowns. Preliminary testing with real data reveals that the use of covariance analysis augmented with reliability analysis may not be sufficient for the complete assessment of parameters and observations. The numerical sensitivity of the matrix of normal equations in adjustments with floating ambiguity parameters is a potential problem that can be detected with the computation of condition numbers. The use of all these analysis tools in standard surveying engineering practice is suggested.