Correlation Analysis of Multipath Effects in GPS-Code and Carrier Phase Observations

Abstract

Multipath error is a limiting factor for successful ambiguity resolution in precise real-time kinematic GPS positioning, both in the carrier phase and pseudorange measurements. Understanding the temporal characteristics of the multipath errors enables the stochastic modelling of these errors. To do this, dual frequency data as well as data from short baselines of several metres apart are observed and analyzed under different multipath conditions. Further, a covariance model (first order Gauss-Markov in this study), accounting for the multipath errors can be created if the temporal characteristics of the multipath errors are derived. The correlation time parameter is an important factor in the analysis of a random process hence this study. Different baselines are observed to estimate the correlation time of the multipath errors. Longer correlation times are obtained in the carrier phase observations due to the double difference process. Not accounting for the long correlation time usually leads to an overestimation of the accuracy and may affect the determination of the ambiguity parameters. This has been shown through a simple numerical investigation.