Drone Lidar Laser Test Flight - Scanning of An Irish Coastline

Here I present a summary of a drone-borne Lidar laser flight test that took place in Ireland on December 2020 based on a concept of practical applications of a Drone-Borne Topography and Bathymetric LiDAR Sensor Technology that uses modified, wave-length selective drone cameras in tandem with specially selected lasers. The laser platform showcased is designed to send laser pulses in 2 circular rings at 2 kHz. The echo signal of each laser signal is digitized and recorded for the entire range gate of 50m. This is the selectable range from which the returning signals can be measured. This range is used to separate echoes from different regions of scattered targets. The determination of accurate bathymetric information using precision laser scanning technology on LiDAR devices is a key element for near offshore activities, hydrological studies such as coastal engineering applications, sedimentary processes, hydrographic surveying as well as archaeological mapping and biological research. UAV imagery processed with Structure from Motion (SfM) and Multi View Stereo (MVS) techniques can provide a low-cost alternative to established shallow seabed mapping techniques offering as well the important visual information. Modern photogrammetry and remote sensing have found small Unmanned Aerial Vehicles (UAVs) to be a valuable source of data in various branches of science and industry (e.g., ecosystem monitoring, agriculture, archaeology and construction). Recently, the growing role of laser scanning in the application of UAVs has also been observed in tandem with conventional 3D scanning using imagery. Drones equipped with specially selected lasers can offer new applications in hydrographic applications such as the production of coastline and inland waterway profiles. The advent of UAVs as carrier platforms of active and passive mapping sensors had a huge impact in the field of photogrammetry and remote sensing. The introduction of Structure-from-Motion (SfM) and Dense Image Matching (DIM) techniques providing automatic orientation of entire image blocks and height estimates for every image pixel has democratized image-based 3D mapping of topography and dramatically increased the achievable point densities. The applicability of UAV-photogrammetry is further facilitated due to the existence of easy-to-use software solutions providing an automated processing chain from captured images to digital surface models, 3D meshes, and orthophoto maps, respectively. While the application of SfM is directly applicable for the dry part of alluvial and coastal areas, mapping of underwater topography requires consideration of beam bending at the air-water medium boundary. Water refraction poses significant challenges on depth determination. This problem has been addressed through customized image-based refraction correction algorithms or by modifying the collinearity equation. It will be the task of image processing to then use a full waveform processing algorithm for analyzing waveforms. Ideally false signals are eliminated and the most probable wave model is determined. Finally, data sets with high accuracy, high resolution and hydrography are provided to support point classification. Machine Learning techniques are constantly being developed to bridge some of the technological gaps in this field. Technology Developed and Tested by MuonRay Enterprises Ireland. (Copyright MuonRay Enterprises Ireland)