Monitoring spatiotemporal variation in beach surface moisture using a long-range terrestrial laser scanner

Support vector regression for high-resolution beach surface moisture estimation from terrestrial LiDAR intensity data

“…Based on the laboratory test results ( Jin et al, 2020 ), the gravimetric moisture contents of the 35 saturated samples were set to 26%. The results were also verified by the field moisture samples collected on the Ostend-Mariakerke and Koksijde-Groenendijk beach, Belgium ( Jin et al, 2020 , Jin et al, 2021 ).…”

“…The average intensity, range and incidence angle of each field moisture sample was extracted from the corresponding TLS point clouds in a 1 × 1 m grid cell, in which the incidence angle was derived based on the plane fitting using the nearby points (to obtain the corresponding normal vector of the fitted plane) ( Jin et al, 2021 ). In this study, only the moisture samples with a scanning range < 250 m (a total of 55 effective samples) were adopted in the next moisture retrieval because the point cloud density at long ranges was too low (especially in the high moisture region) to obtain an accurate incidence angle ( Jin et al, 2021 ).…”

“…It should be said that the moisture distribution of these field samples was relatively concentrated, mainly at the ranges of 0–1% and 15–20%, due to the collection from the established sampling grid at low tide each day ( Jin et al, 2021 ). Only a few samples with saturated moisture were collected during the TLS measurements (even no high moisture samples at the ranges > 350 m).…”

“…Recently, terrestrial laser scanning (TLS) has shown great promise for an accurate BSM estimation because of the advantages of active scanning (deployable at daytime and nighttime), high spatial and temporal resolution (through continuous measurements) ( Jin et al, 2020 , Jin et al, 2021 , Nield et al, 2014 , Ruessink et al, 2014 , Smit et al, 2018 , Tan et al, 2020 ), as well as a large spatial scale (long-range LiDAR systems can typically measure a large beach section, such as 400 × 800 m, with a single scan). According to the radar range equation, the backscattered intensity is closely related to the target surface reflectance, and the latter could theoretically be used to derive the BSM when other surface properties remain constant ( Nolet et al, 2014 ).…”

Environmental Influences on the Stability of a Permanently Installed Laser Scanner

“…Object properties can be observed especially in the case of heavy rain. Changes in soil moisture on the beach influence reflective properties as for example reported by Jin et al (Jin et al, 2021) and rain water collecting on paved surfaces prevents capturing them with laser scanning.…”