ADVANCES IN REAL-TIME GPS DEFORMATION MONITORING FOR LANDSLIDES , VOLCANOES , AND STRUCTURES

The timely identification of deformation associated with geologic hazards or ground settlement can save lives, avert large financial liabilities and avoid severe environmental damage. Until recently, deformation monitoring could only be accomplished by periodic optical surveys or by using electronic sensors (tiltmeters, TDR, electrodes, etc). Periodic surveys do not provide a real-time warning capability and automated sensors, though providing continuous data, do not yield conclusive information about displacement vectors. A recent development in GPS processing software described in this paper provides reliable, precise, real-time, automated 3D monitoring at the millimeter level. The unique software design, called control station processing (CSP), uses sophisticated processing of raw GPS data at a control station computer. The powerful CSP algorithms are virtually immune to potential false alarms or interruptions to continuous monitoring (such as cycle slips) that plague less robust GPS processing strategies, such as RTK. The CSP described here handles data from numerous receivers simultaneously and provides a comprehensive Internet-enabled automatic warning system. The result is a deformation monitoring system with unique new capabilities. Currently installed CSP systems show reliable 3D data at the millimeter-level that are not plagued by artificial position jumps. Data from monitoring an active landslide for fourteen months demonstrates that it is possible to monitor motion rates at the millimeter level with vector directions consistent with landslide failure models. GPS provides cost-effective and heretofore-unavailable 3D information that will revolutionize the geohazards-warning mission of engineering geologists.