Simulation of sea surface wave influence on small target detection with airborne laser depth sounding

Abstract

A theoretical model for simulation of airborne depth-sounding lidar is presented with the purpose of analyzing the influence from water surface waves on the ability to detect 1-m3 targets placed on the sea bottom. Although water clarity is the main limitation, sea surface waves can significantly affect the detectability. The detection probability for a target at a 9-m depth can be above 90% at 1-m/s wind and below 80% at 6-m/s wind for the same water clarity. The simulation model contains both numerical and analytical components. Simulated data are compared with measured data and give realistic results for bottom depths between 3 and 10 m.

Wa-LiD: A New LiDAR Simulator for Waters

“…The waveforms received by the LiDAR system (power as a function of time) are written as the sum of the echoes of multiple waves [7]:…”

“…The potential for airborne hydrographic LiDAR is that it can be used for both altimetry and bathymetry because of the ability of LiDAR detectors to register returned signals from (i) the water surface for altimetry [5], (ii) the water bottom for bathymetry ([6], [7]), and (iii) the water column that allows some optical properties of water to be deduced [8]. The Airborne Hydrographic LiDAR technique is limited in terms of spatial coverage and because the data is expensive to gather.…”

“…Before now, few studies have been published that model LiDAR waveforms on water; these studies include (i) the simulation model of Mclean [10], which generates LiDAR returned waveforms from a wind-roughened ocean, (ii) the work of Feigels [6] on the optimisation of airborne LiDAR's parameters through modelling and analysing waveforms and (iii) work on modelling sea surface return and laser bathymetry from airborne LiDAR [7].…”

“…This model is similar to other Hydrographic LiDAR models (e.g., [5], [6], [7]) except it integrates radiative transfer laws governed by the physical properties of water for any wavelength. This simulation model uses a geometrical representation of the water surface with the geometric model of Cook and Torrance [11] and integrates both the characteristics of detection noise and signal level due to solar radiation.…”

The Effect of Surface Waves on Airborne Lidar Bathymetry (ALB) Measurement Uncertainties

“…Increasing wind speeds also impedes target detection capability that is important for navigation application and bottom analysis. It has been shown in [14] that higher wind speeds decrease the probability of detecting a 1 m 3 cube. The surface waves have also been demonstrated to increase the variance in the ray-path length for laser beams with smaller beam footprints [15].…”