Measuring Surface Moisture on a Sandy Beach based on Corrected Intensity Data of a Mobile Terrestrial LiDAR

Abstract

Surface moisture plays a key role in limiting the aeolian transport on sandy beaches. However, the existing measurement techniques cannot adequately characterize the spatial and temporal distribution of the beach surface moisture. In this study, a mobile terrestrial LiDAR (MTL) is demonstrated as a promising method to detect the beach surface moisture using a phase-based Z&F/Leica HDS6100 laser scanner mounted on an all-terrain vehicle. Firstly, two sets of indoor calibration experiments were conducted so as to comprehensively investigate the effect of distance, incidence angle and sand moisture contents on the backscattered intensity by means of sand samples with an average grain diameter of 0.12 mm. A moisture estimation model was developed which eliminated the effects of the incidence angle and distance (it only relates to the target surface reflectance). The experimental results reveal both the distance and incidence angle influencing the backscattered intensity of the sand samples. The standard error of the moisture model amounts to 2.0% moisture, which is considerably lower than the results of the photographic method. Moreover, a field measurement was conducted using the MTL system on a sandy beach in Belgium. The accuracy and robustness of the beach surface moisture derived from the MTL data was evaluated. The results show that the MTL is a highly suitable technique to accurately and robustly measure the surface moisture variations on a sandy beach with an ultra-high spatial resolution (centimeter-level) in a short time span (12 × 200 m per minute).

Sensitivity of Near-Infrared Permanent Laser Scanning Intensity for Retrieving Soil Moisture on a Coastal Beach: Calibration Procedure Using In Situ Data

“…The angle of incidence influences the maximum distance over which a TLS can accurately measure surface moisture [62], and it depends on the target's physical properties and geometrical conditions [79]. For Nield [61] and Smit [62], the influence of the incidence angle was not relevant when using the TLS for soil moisture estimation on a sandy beach surface; Jin [69] considered this aspect relevant, and he carried out a series of indoor calibration experiments with the purpose of understanding the dependence of I on the incidence angle under the same gravimetric moisture conditions.…”

“…The relation between I, the range, and the incidence angle can be expressed with the simplified equation [69]:…”

“…Nield et al [29,61] demonstrated the potential of TLS for measuring the moisture in a sandy environment using a Leica Scanstation2 with a wavelength of 532 nm. Smit et al and Ruessink et al [62,63] used a RIEGL VZ-400 with 1550 nm wavelength to reveal a robust negative relation between TLS backscatter intensity and surface moisture in the moisture range of 0-25% between 20 and 60 m. Recently, Jin et al [69] demonstrated the possibility of spatially mapping moisture using a mobile TLS Z&F/Leica HDS6100 with a wavelength of 650-690 nm. The moisture content of the sand was up to 25%, and the scanning distance was from 1 to 20 m. The application of TLS in aeolian environments also shows how surface topography and moisture patterns co-evolve [61].…”

Lithodynamic Processes along the Seashore in the Area of Planned Nuclear Power Plant Construction: A Case Study on Lubiatowo at Poland

“…On the other hand, the resultant (net) longshore sediment transport calculated with Bijker's model [27] for the seawards shore of the Hel Peninsula in the Jastarnia region was 128,000 m 3 /year. Other computations of this type and estimations based on measurements of the amount of material deposited in the western part of the Władysławowo port were collated in the study [28,29]. Depending on the computational methodology adopted by various authors, the volume of sediment transport ranged from 90,000 to about 150,000 m 3 /year, while that determined on the basis of measurements of sediment deposited in the western part of the port varied from 70,000 to 120,000 m 3 /year.…”

Novel Trajectory Optimization Algorithm of Vehicle-borne LiDAR Mobile Measurement System

“…Vehicle-mounted mobile measurement systems have been employed for studies on the construction of smart cities, (1,2) city transportation programming, (3) the modeling of highways, (4) cadastral surveys, (5) and other fields owing to their high degree of automation, short data generation cycle, low cost, and high flexibility. (6,7) The ever-changing operating environment of vehicle-mounted mobile measurement systems will have a great impact on data accuracy and may even produce unpredictable errors. Therefore, the point cloud should be modified in addition to performing standard operations to ensure that the mathematical accuracy meets the requirements.…”