The Use of Green Laser in LiDAR Bathymetry: State of the Art and Recent Advancements

Abstract

Bathymetric LiDAR technology is a technology used for simultaneous data acquisition regarding the morphology of the bottom of water reservoirs and the surrounding coastal zone, realized from the air, e.g., by plane or drone. Contrary to the air topographic LiDAR, which uses an infrared wavelength of 1064 nm, bathymetric LiDAR systems additionally use a green wavelength of 532 nm. The green laser can penetrate the water, which makes it possible to measure the depth of shallow water reservoirs, rivers, and coastal sea waters within three Secchi depths. This article presents the theoretical basis for the construction of a green laser. Against the background of other methods of measuring the bottom of water reservoirs, the technology using waves from the visible light range is presented in detail in the assessment of the bottom morphology of shallow water reservoirs. The possibilities of using green laser in lidar bathymetry implemented in particular in non-navigable regions are shown. The results of the researchers’ work on river processes (erosion, sedimentation), design of stream restoration, determination of morphometric parameters of the riverbed, as well as assessment of the topography of the marine coastal bottom zones are summarized. The development direction of lidar bathymetry is discussed.

Comparative Analysis of Digital Elevation Model Generation Methods Based on Sparse Modeling

“…The dictionary is a redundant DCT dictionary, that is, a standard dictionary used in image compression such as JPEG (Figure 4). From the obtained sparse coefficients x i and dictionary A, the topography of the corresponding patch can be reproduced and interpolated as ŷi using Equation (2). ŷi…”

“…the topography of the corresponding patch can be reproduced and interpolated as 𝐲 using Equation (2). The value of each mesh in the DEM is obtained by averaging the values of the corresponding cells in all patches containing that mesh.…”

“…Aerial laser surveying and aerial laser bathymetry (ALB) have been widely used to create DEMs. For example, ALB data can be used for various purposes [2], such as in sediment volume surveys of dams and rivers and seafloor surveys for offshore construction. However, in these measurements, cases occur where measurement data are missing owing to topographic surface conditions, or obstructions [3].…”

Low-Tech and Low-Cost System for High-Resolution Underwater RTK Photogrammetry in Coastal Shallow Waters

“…Coastal seabed mapping and bathymetry restitution is a key issue for environmental and human activities, including evolution of morphodynamic features (dunes, ripples), coral reef structures, marine habitat characteristics, navigation safety, coastal protection, etc. Coastal bathymetry is mainly performed using multi-beam echo-sounder (MBES) with possible combination with side-scan sonar (e.g., [1][2][3]) or bathymetric LiDAR (e.g., [4][5][6]). Both are active remote sensing techniques: MBES uses acoustic signal emitted from a boat, whereas LiDAR uses optical signal emitted from an aircraft.…”

Concept of an Innovative System for Dimensioning and Predicting Changes in the Coastal Zone Topography Using UAVs and USVs (4DBatMap System)

“…Airborne LiDAR Bathymetry (ALB)/Airborne LiDAR Hydrography (ALH) involve determining the depths of a waterbody by measuring the time difference between the moments of reception of two pulses recorded by the on-board sensors of a manned aircraft [41]. The advantage of the ALH/ALB systems is the full coverage of the bottom with measurements, the accuracy of which, however, depends on water transparency [42].…”