Demonstration of Two Portable Scanning LiDAR Systems Flown at Low-Altitude for Investigating Coastal Sea Surface Topography

Abstract

Abstract:We demonstrate the efficacy of a commercial portable 2D laser scanner (operating at a wavelength close to 1,000 nm) deployed from a fixed-wing aircraft for measuring the sea surface topography and wave profiles over coastal waters. The LiDAR instrumentation enabled simultaneous measurements of the 2D laser scanner with two independent inertial navigation units, and also simultaneous measurements with a more advanced 2D laser scanner (operating at a wavelength near 1,500 nm). The latter scanner is used routinely for accurately measuring terrestrial topography and was used as a benchmark in this study. We present examples of sea surface topography and wave profiles based on low altitude surveys (< ~300 m) over coastal waters in the vicinity of Cape de Couedic, Kangaroo Island, South Australia and over the surf zone adjacent to the mouth of the Murray River, South Australia. Relative wave heights in the former survey are shown to be consistent with relative wave heights observed from a waverider buoy located near Cape de Couedic during the LiDAR survey. The sea surface topography of waves in the surf zone was successfully mapped with both laser scanners resolving relative wave height variations and fine structure of the sea surface to within approximately 10 cm. A topographic map of the sea surface referenced to the airborne sensor frame transforms to an accurate altimetry map which may be used with airborne electromagnetic instrumentation to provide an averaged altimetry covering a portion of the larger electromagnetic footprint. This averaged altimetry is deemed to be significantly more reliable as a measurement of OPEN ACCESS Remote Sens. 2011, 3 1984 altimetry than spot measurements using a nadir-looking laser altimeter and would therefore improve upon the use of airborne electromagnetic methods for bathymetric mapping in surf-zone waters. The aperture range of the scanner does not necessarily determine the swath. We observed that instead, the maximum swath at a given altitude was limited by the angle of incidence of the laser at the water surface.

Sea Surface Altimetry Based on Airborne GNSS Signal Measurements

“…Through processing the experimental data it is demonstrated that the LiDAR data not only can serve as a reference for mean sea level (MSL), but they also provide the statistics of the sea surface roughness, including the significant wave head (SWH), the root-mean-square (RMS) wave height, and the maximum wave height. Note that there are a significant number of reports in the literature on using LiDAR for sea surface topography (Reineman et al 2009 andVrbancich et al 2011). It is observed that there is good agreement between the wave head statistics calculated from the LiDAR data and those obtained from a Waverider buoy.…”

Applying uncertainties to ocean colour data

“…For wave tank measurements, a refraction gauge using an extended light source can also be used (Jähne and Riemer, 1990). In the field, stereophotogrammetry Gallego et al, 2011) or airborne lidar altimetry (Hwang et al, 2000;Vrbancich et al, 2011) enable direct measurement of the surface topography, from which the spectrum can be calculated. In principle the full spectrum, and not just slope statistics, can be retrieved from sun glint data (Cureton et al, 2007;Alvarez-Borrego and Martin-Atienza, 2010).…”

Surf Zone Mapping Using Multirotor Unmanned Aerial Vehicle Imagery

“…Data that can be transferred into the digital format are very important for acquiring spatial information of the earth surface. There are a variety of methods nowadays to obtain spatial data stored in databases such as GIS, remote sensing, LIDAR, laser scanning, conventional surveying, and aerial photogrammetric survey [9]. This research is focused on the use of photogrammetry method to produce 3D model maps of the earth surface using images.…”