Simulation and experiment analysis of dynamic deformation monitoring with the integrated GPS/pseudolite system

Abstract

The precision of displacement monitoring for deformable objects with global positioning system (GPS) is severely affected in highly occluded spaces, such as urban canyons and surface mines. This phenomenon is attributed to the presence of few visible GPS satellites with poor geometric structures, thus leading to ineffective positioning in severely occluded areas. An integrated GPS/pseudolite positioning technique is proposed in this paper as an effective solution for precision deformation monitoring in the abovementioned areas. This technique can effectively increase the number of visible satellites, optimize their geometric structure, and improve their positioning precision and reliability. This technique has been used in monitoring related deformable objects and has yielded favorable results. However, the majority of current studies have focused on static positioning, whereas dynamic positioning has largely been ignored. Furthermore, dynamic positioning requires further research to eliminate or reduce unmodeled systematic errors (particularly the multipath error). This paper explains the necessity and effectiveness of pseudolite introduction on the basis of the derivation of the basic deduction formula for integrated GPS/pseudolite positioning. Thereafter, the importance of pseudolite location selection by simulated test verification and analyses is discussed. Several methods for estimating and reducing the multipath error of pseudolite, which is affected by slow or small ground surface deformation and shows high spatial correlation, are also presented in this paper. A dynamic deformation monitoring model is proposed on the basis of the moving average method to improve the precision of dynamic positioning. The standard deviations of the baseline vectors in the X, Y, and Z directions are calculated at 14.0, 35.3, and 9.0 mm, respectively, thus indicating that the positioning precision is improved to different degrees in the proposed model compared with that of the separate GPS system (33.8, 54.4, and 22.3 mm for the X, Y, and Z directions, respectively), the integrated GPS/pseudolite dynamic positioning model prior to the elimination of the multipath errors of pseudolites (24.9, 56.4, and 13.3 mm for the X, Y, and Z directions, respectively), and the integrated GPS/pseudolite dynamic positioning model on the basis of the estimation of multipath error parameters (29.7, 47.9, and 17.8 mm for the X, Y, and Z directions, respectively).