Applications of pseudolites for deformation monitoring systems

Due to the high precision of the carrier phase observables, the Global Positioning System (GPS) technology has been widely used for measuring crustal motion and ground subsidence, and more recently for monitoring deformation of man-made structures such as bridges, dams, buildings, etc. It is well known that for such GPS-based deformation monitoring systems, the accuracy, availability, reliability and integrity of the positioning solutions is heavily dependent on the number and geometric distribution of satellites being tracked. However, in some situations, such as in urban canyons, dam monitoring in valleys and in deep open-cut mines, the number of visible satellites may not be sufficient to reliably determine precise position. Indoors the task is impossible. Pseudolites, which are ground-based transmitters of GPS-like signals, can significantly enhance the satellite geometry, and even replace the GPS satellite constellation in some situations (such as deformation monitoring indoors). There are three general classes of the potential pseudolite applications in deformation monitoring systems. The first case is GPS augmentation with pseudolite(s), which is suitable for circumstances such as urban canyons, or monitoring in valleys and deep open-cut mines. The second case is indoor applications o