Integrated GPS And Pseudolite Positioning For Deformation Monitoring System

Traditional surveying techniques have been more and more difficult to meet the requirements of large-scale deformation monitoring such as dams and landslides in continuity, real time and automation. GPS is an advanced tool for deformation monitoring, and it has been widely applied in geodetic survey, crustal movement monitoring and precise engineering survey. For deformation monitoring of dams and slopes, GPS has already proven to be convenient in data collection, data transmission, data processing and analysis. However, it has problems on the accuracy, reliability as well as the high cost. Under poor observation environments, GPS positioning accuracy decreases significantly because GPS signal is blocked. Moreover, the positioning accuracy of the height component is generally 2 or 3 times worse than the horizontal component due to the limitations of satellite geometry. Furthermore, GPS has still not been used in some areas such as underwater, underground, indoor or tunnels.Pseudolite positioning technique is an effective tool to solve GPS problems above. Pseudolites can increase the number of satellites and improve the geometry. This dissertation will investigate the integration of GPS and pseudolites to improve the positioning accuracy, especially the vertical accuracy in order to meet the requirements of dam and slope deformation monitoring systems. The emphasis in this work has been placed on1. Basic principles and pseudolite signal structure and navigation data were described. Some key issues in the applications of pseudolites, such as the scheme of GPS and pseudolite integration, the near-far problem, pseudolite tropospheric delay, pseudolite synchronization and multipath effects were discussed in detail. Several requirements of pseudolite stations were also proposed in this work.2. Based on the integration of GPS and pseudolites, Geometric DOP was investigated to compare effects of the additional pseudolite observations. The estimations of GDOP and VDOP maximum values were given, and the relationship between GDOP and RGDOP was also demonstrated. These results indicated that the positioning accuracy was improvement by pseudolites augmentation.3. Different observation models for GPS and pseudolites integrated system under different situations were built. Similarities and differences of error characteristics of GPS and pseudolites were compared. The estimation equations for pseudolites tropospheric delay and multipath bias in static environment were also given. Moreover, an effective way was proposed to estimate the parameters of pseudolite clock bias and clock drift by data fitting.4. Based on the observations and error models, a software package for data processing of an integrated GPS and pseudolite system was successfully developed by the author. Some key modules such as ambiguity resolution, cycle slip recovery, tropospheric delay and multipath bias mitigation were demonstrated in this work.5. A static field test was carried out to evaluate the practical effect of GPS and pseudolite integrated positioning system in poor observation environments. And the experimental data has been processed under different scheme using the software developed. It can be seen from the results that the augmentation of pseudolite can improve dramatically positioning accuracy when the pseudolite multipath biases were calibrated in advance.