IMPLEMENTATION OF LOW-COST DIFFERENTIAL GPS NETWORKS TO MONITOR DISPLACEMENTS OF A LANDSLIDE

Instrumentation on unstable slopes is often used to provide advanced warning of movements and develop an understanding of the kinematics of landslides. Many instruments are capable of these measurements (ShapeAccelArrays, etc.), but the expense of installation often limits these technologies to very few locations on the landslide. Remote sensing has become an invaluable tool for investigating the distribution of displacements over large areas, but as of yet, these measurements require a manual operation that results in relatively infrequent data collection. The French Institute of National Geographic (IGN, Institut Géographique National) has developed a new high-resolution GPS named GeoCubes, and it has recently become commercially available through the company Kylia. The GeoCube consists of a network of two or more low-cost GPS units that measure their position at a relatively high frequency and conduct analysis that results in millimeter accuracy. The low cost of this system and the scalability with additional GPS units allow a higher density of measurement points to be installed on a sloped surface, with automated near-real time monitoring. It thus provides many of the benefits of both installed instrumentation and remote sensing in a quickly deployable and relatively inexpensive landslide monitoring system.

Research being conducted at the University of Alberta, with the Canadian National Railway, the Geological Survey of Canada through the Railway Ground Hazard Research Program, has been evaluating the use of these GeoCube systems. This evaluation has included the installation of a GeoCube network of 11 units at the 10-mile slide near Lillooet, BC. This landslide has complex kinematics as it is composed of many large moving blocks of soil. The system records the coordinates of the 11 GPS units and calculates the displacements for 10 units relative to 1 unit at a fixed location. The evaluation of the GeoCubes has focused on ease of installation, survivability in the local climate, the ability to assess trends and magnitudes of slope movements measured by other means, and accuracy relative an RTK GPS systems. This presentation will show the lessons learned, improvements made to the system, and the assessment of the benefits and accuracy of the GeoCube system.