Ground-based Interferometric Radar for Rockfall Hazard Monitoring
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2015-05-06
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Abstract:Rockfall events along transportation corridors are a major public safety hazard and can result in significant economic costs due to traffic delays and road repairs. Transportation agencies are in need of innovative technologies to identify and monitor rockfall hazards. Ground-based interferometric radar (GBIR) is an emerging remote-sensing technology that can be used to rapidly scan large regions and detect very small (millimeter-scale) surface deformations from small shifts in phase of the reflected radar signal. Previous applications of GBIR have focused primarily on monitoring large spatial movements, such as landslides, where the area of movement may be hundreds or thousands of square meters. Application of GBIR to rockfall hazards requires detecting minute movements occurring over a very small spatial scale (a few square meters). The objective of this study was to evaluate the threshold for detecting movements of individual boulders as a function of boulder size, the magnitude of movement, and the offset distance. Boulders, ranging from about 0.5 to 5 meters in surface dimensions, were moved in small mm-scale increments. Two GBIR devices setup at different viewpoints scanned a region covering approximately 20,000 m2 after each controlled boulder movement. Interferograms developed from imagery collected before and after each movement of the largest boulders (2m to 5m in surface dimensions) showed clear phase anomalies associated with the boulder movement, while phase anomalies associated with movements of smaller boulders were not as clearly discernable. The movement magnitudes recorded with the GBIR were generally consistent with the expected values based on ground truth measurements.
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