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Effect of terrestrial LiDAR point sampling density in ephemeral gully characterization

Momm, Henrique G., Bingner, Ronald L., Wells, Robert R., Dabney, Seth M., Frees, Lyle D.
Open Journal of Hydrology 2013 v.3 no.1 pp. 38-49
agricultural land, data collection, gully erosion, hydrology, lidar, ravines, roughness, sediments, soil, surveys, technology, topography
Gully erosion produces significant amounts of sediment from agricultural landscapes, but is difficult to monitor and quantify with existing technology. Scientific investigations of gullies depend on accurate and detailed topographic information to understand and evaluate the complex interactions between field topography and gully evolution. Detailed terrain representations can be produced by new technologies such as ground-based LIDAR systems. These systems are capable of collecting information with a wide range of ground point densities as a result of operator controlled factors such as the area of data collection (scan angle), average point density of scans, and degree of overlap between scans. Increasing the point density results in more time needed to complete field surveys with more information resulting in increased complexity of data post-processing. In this study, the effect of point sampling density on the capability to collect topographic information was investigated at individual gully scale. This was performed through the utilization of semivariograms to produce overall guiding principles for multi-temporal gully surveys based on various levels of laser sampling points and relief variation (low, moderate, and high). For each level considered, theoretical variograms were derived from experimental variograms to compare with varying percentages of randomly selected subsets of points. Results indicated a point sampling density threshold that produces little or no additional topographic information when exceeded. A reduced dataset was created using the density thresholds and compared to the original dataset with no major discrepancy. Although variations in relief and soil roughness can lead to different point sampling density requirements, the outcome of this study serves as guidance for future field surveys of gully evolution and erosion.