SGER: An Investigation of Landslide Assessment and Delineation Using Airborne Laser Swath Mapping

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Landslides can cause extensive damage; hence early detection, monitoring and assessment of potential problem areas are critically important. The ability to recognize impending slide locations would assist mitigation, thereby reducing major landslide development, disruption of services and possible loss of life. The first step in the characterization of a landslide prone area is the contour mapping of its surface. However, due to the varied topography, standard surveying techniques rarely provide contour intervals smaller than 3 m (10 ft). Unfortunately, this resolution is unsuitable for delineation of future landslide development and remedial measures. However, recent advances in microcomputers, lasers and GPS positioning technology, have resulted in the development of a compact, lightweight, airborne laser mapping system that can be operated from a small airplane. It allows one to map 100 square kilometers in a single hour, and ultimately create a three-dimensional surface map made up of data points spaced 1-meter apart. In addition to rapid data collection, vertical accuracies of 5 to 10 cm. (2 to 4 inches) are usually possible. During a flight, the laser sends out pulses that hit the ground surface and are reflected back to the plane. By measuring the time it takes the pulses (10,000 per second) to complete the roundtrip determines how far away each point is from the aircraft. Then, by knowing where and how high the aircraft is, allows one to compute the absolute height and coordinates of the ground surface. Several GPS systems both in the aircraft and on the ground (ground crews) provide precise location information of the aircraft's position at all times. The goal of this research is to assess the accuracy and capability of airborne laser swath mapping (ALSM) to identify and map landslide areas. Selected areas in South Dakota's Missouri River valley will be used as test sites. A series of measurement and mapping strategies will be performed to determine the most efficient, highest sensitivity, and cost effective approach to assess and monitor landslide areas. Once this is accomplished, an evaluation of the data will then be performed to establish those pertinent parameters necessary to characterize landslides.