Effect of Terrestrial LiDAR Point Sampling Density in Ephemeral Gully Characterization

Abstract

<p class="MsoNormal"> <span lang="EN-US">Gully erosion can account for significant volumes of sediment exiting agricultural landscapes, but is difficult to monitor and quantify its evolution with traditional surveying 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 terrestrial LiDAR sys</span><span lang="EN-US">tems. These systems are capable of collecting information with a wide range of ground point sampling densities as a result of operator controlled factors. Increasing point density results in richer datasets at a cost of increased time needed to complete field surveys. In large research watersheds, with hundreds of sites being monitored, data collection can be</span><span lang="EN-US">come costly and time consuming. In this study, the effect of point sampling density on the capability to collect topog</span><span lang="EN-US">raphic information was investigated at individual gully scale. This was performed through the utilization of semi</span><span lang="EN-US">-</span><span lang="EN-US">variograms to produce overall guiding principles for multi-temporal gully surveys based on various levels of laser sam</span><span lang="EN-US">pling points and relief variation (low, moderate, and high). Results indicated the existence of 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 practical guidance for future field surveys of gully evolution and erosion.</span><span lang="EN-US"><o:p></o:p></span> </p

Gully erosion processes, disciplinary fragmentation, and technological innovation

“…Marzolff and Poesen (2009) employed UAVs (unmanned aerial vehicles) and photogrammetry to define gully erosion processes using decimeter-scale grids with centimeter-scale errors. Ground-based LiDAR, photogrammetry, and hand-held devices can now describe ephemeral gully erosion using millimeter-scale grids with millimeter-scale errors 49 INTERNATIONAL GULLY EROSION SYMPOSIUM (Momm et al, 2013a;Wells et al, 2017;Castillo et al, 2018). Moreover, the cost of such technology could be as little as $6000 for all hardware and software required for a selfcontained, ground-based photogrammetric system (Kršák et al, 2016;Wells et al, 2016; see also Castillo et al, 2015Castillo et al, , 2018.…”

Quantifying uncertainty in high-resolution remotely sensed topographic surveys for ephemeral gully channel monitoring

“…Upstream Robson, 2012, 2014), and DEM spatial resolution (Zhang and Montgomery, 1994;Kienzle, 2004;Momm et al, 2013a). The majority of previous studies have focused on accuracy evaluation of a specific photogrammetric survey method at a single time period.…”

“…At a finer scale, investigation of ground-based and terrestrial lidar has demonstrated a high locational accuracy (∼ 2 mm) and noted the importance of appropriate spatial sampling density for ephemeral and classical gully investigation (Momm et al, 2013a). Topographic representations of gully channels require datasets with a specific minimum sampling density, which is dependent on site-specific topographical characteristics (Castillo et al, 2012;Momm et al, 2013a).…”

“…Topographic representations of gully channels require datasets with a specific minimum sampling density, which is dependent on site-specific topographical characteristics (Castillo et al, 2012;Momm et al, 2013a). Overlapping the same area with multiple scans increases the overall sampling density and assists in occlusion and shadow avoidance while normalizing spatial resolution.…”

GIS-Based Detection of Gullies in Terrestrial LiDAR Data of the Cerro Llamoca Peatland (Peru)

“…[34]) and gully edge detection as future research topics. The study of [35] assesses the effect of TLS point sampling density on the characterization of ephemeral gullies within areas of agricultural land use. They outline guidance principles for multitemporal gully LiDAR surveys in order to minimize scanning effort while keeping the required topographic details as high as possible.…”