Effects of Site-Dependent Errors on the Accuracy of C/A Code DGPS Positioning

Thilantha Lakmal Dammalage

doi:10.28991/cej-03091159

Abstract

Several differential GPS processing techniques can be used; for instance, single differencing and double differencing, which are popular in practice. Irrespective of the DGPS processing technique used, the ultimate accuracy of the user-location depends on the existence of non-common or site-dependent errors, which occur at the points of observation and the reference. Of these, the most common and dominant site-dependent error is the multipath. Therefore, this research evaluates the effects of site-dependent errors on C/A code differential GPS correction accuracies by providing special emphasis on the multipath error. For the analyses, four segments of about 24-hour continuous static C/A code based DGPS observations were conducted at three precisely known ground stations and four different multipath environments were introduced by placing three different types of artificial signal reflectors at one of the observation stations. By using the known GPS receiver-reflector configuration, pseudo-range multipath was precisely calculated for each observation segment. C/A code DGPS positioning accuracies before and after multipath mitigation were presented by evaluating the effect of the most dominant site-dependent error, i.e., multipath, on C/A code DGPS correction accuracies.

Highlights

Differential GPS (DGPS) can be considered as the most effective technique that minimizes or completely remove the influence of almost all common mode errors from GPS observations [1]
The GNSS market report published by the European GNSS Agency in 2015 illustrates that more than 91% of the GNSS devices are being used in location-based services (LBS) and vehicle navigation as of 2015
Four segments of about 24 hours continuous static observations were conducted by introducing four different multipath environments to one selected GPS reference station, and the observations were made by placing three types of artificial signal reflectors to result in three different observation segments with multipath error and the fourth segment to be observed without a signal reflector, to have the minimum effect of multipath error on observations

Summary

Introduction

Differential GPS (DGPS) can be considered as the most effective technique that minimizes or completely remove the influence of almost all common mode errors from GPS observations [1]. The non-common errors (multipath, receive and measurement noises), which affect the observation of the reference station contributes as accuracy diminishing factors for DGPS correction data estimations [11]. Based on the above facts, most permanent GPS reference stations are capable of calculating its correction data with particular reference to common mode errors by minimizing the effect of multipath through careful site selection and/or augmentation with additional hardware such as utilizing choke-ring antennas [10]. For some GPS applications, the estimation of precise carrier phase DGPS correction is crucial; for instance, in deformation or landslide monitoring and large structure dynamic monitoring, where most analyses and predictions are based on the noisy-like variation of the position of observation In these cases, it is critical to correctly interpret the actual observations as closely as possible by eliminating the combined residual effects of multipath and other systematic errors. An experiment was designed to investigate the effect of most dominant noncommon or site-dependent error, multipath, on C/A code DGPS corrections

Research Methodology and Data Acquisition

Analysis of Results

Findings

Conclusion