Modeling of GPS Systematic Errors in Monitoring and Control Surveys

Abstract

The accuracy of Global Positioning System (GPS) relative positioning depends on the geometric distribution of the observed satellites and on the quality of the observations. Different types of errors affect GPS relative positioning in different ways. Some of the errors may have systematic effects on the measured baselines, which may produce significant scale errors and rotations. These effects, however, may change from one survey epoch to another due to a change in the error characteristics and/or the sky distribution of the observed satellites. Therefore, they cannot be completely canceled out in the computation of deformations. In monitoring and engineering surveys of high precision, these effects must be modeled and eliminated. This paper discussed the effects and their modeling. As an example, a GPS ground‐subsidence monitoring network in Venezuelan oil fields was analyzed. Rotation of up to 6 ppm in a vertical plane was obtained between survey campaigns in 1990 and 1991. To significantly minimize these systematic effects, some recommendations are made for the design of monitoring schemes and control networks for large engineering projects.