Abstract
Multi-temporal airborne laser scanning (ALS) surveys have become a prime consideration for detecting landslide movements and evaluating landslide risk in mountain areas. The minimum elevation change (or detectability) that can be detected by repeated ALS surveys has become a critical threshold for landslide researchers and engineers to decide if ALS is a capable tool for detecting targeted landslides and arranging the minimum time span between two scans if ALS is a choice. The National Center for Airborne Laser Mapping (NCALM) at the University of Houston conducted three repeated ALS surveys at the Slumgullion landslide site in Colorado, U.S. over one week in July of 2015. These repeated ALS surveys provide valuable datasets for evaluating the vertical detectability of multi-temporal ALS surveys in a typical mountain area. According to this study, the difference of digital elevation models (DDEM) derived from ALS has the ability of detecting a minimum elevation change of 5 cm over flatter and moderately rugged terrain areas (slope < 20 degrees) and a minimum of a 10-cm elevation change over rugged terrain areas (20 degrees < slope < 40 degrees). However, the DDEM values over highly rugged terrain areas (slope > 40 degrees), such as cliff and landslide scarps, should be interpolated with caution. Global Navigation Satellite Systems (GNSS) and Terrestrial Laser Scanning (TLS) surveys were also performed at the middle portion of the landslide area for assessing the accuracy of ALS datasets. The accuracy of ALS varies from approximately one decimeter (~10 cm) to one foot (~30 cm) depending on the roughness of terrain surface and vegetation coverage (point density). The detectability and accuracy estimates of ALS measurements obtained from the case study could be used as a reference for estimating the performance of modern ALS in mountain areas with similar topography and vegetation coverage.
Highlights
The use of airborne Light Detection and Ranging (LiDAR), called airborne laser scanning (ALS), for topographic mapping, is rapidly becoming a standard practice for landslide investigations.The ability to use ALS to measure terrain surface elevations beneath a vegetated canopy has significantly advanced mountain landslide studies (e.g., [1,2,3,4,5,6])
Mountain landslides are often accompanied by significant elevation changes, which can be detected by differing repeated ALS surveys
difference of digital elevation models (DEMs) (DDEM) values over 70% of the scan area are within ±5 cm and the values over 90% of the whole scanned area are within ±10 cm
Summary
The use of airborne Light Detection and Ranging (LiDAR), called airborne laser scanning (ALS), for topographic mapping, is rapidly becoming a standard practice for landslide investigations. The precision and accuracy of ALS measurements are two fundament parameters for understanding the detectability of DDEM maps. DDEM maps derived from repeated ALS surveys may achieve exceptionally high accuracies in the detection of ground elevation changes. The National Center for Airborne Laser Mapping (NCALM) at the University of Houston conducted three repeated ALS surveys over the Slumgullion landslide area in Lake City, Colorado, see Figure 1, on 3, 7, and 10 July 2015. These three TLS datasets were collected by the same field crew with the same equipment and were post-processed with identical procedures They provide valuable datasets for evaluating the repeatability (precision) of model ALS surveys in a typical mountain landslide area. These ground truth measurements provide fundament performed at the middle portion of the landslide area during the ALS surveys These ground truth datasets to assess the accuracy of the ALS datasets. The Slumgullion landslide has abeen site for ground-based, andground-based, space-borne remote sensing (e.g., remote [25,26,27]).sensing studies frequently utilized as aairborne, test site for airborne, and studies space-borne (e.g., [25,26,27])
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