Water Depth Evaluation using Aerial Image Sensing and Infrared Laser Scanning

Abstract

 The Airborne lidar bathymetry (ALB) has recently attracted attention because it can simultaneously survey land and water areas in a short time. However, it is known that the absence of measurement may occur when the turbidity is high. In this study, we developed a method to compensate the water depth from the output of an aerial photogrammetry camera and a near infrared laser scanner attached to the ALB system. A series of ortho-images obtained from a camera was extracted, a long wavelength component image was prepared by applying a 2D Fourier transform and a low-pass filter, and wavelength and wave celerity were obtained by a lag correlation method. Simultaneous wave profile data on elliptic circle were prepared by applying a spatio-temporal binning method for the output of a laser scanner, and the wave direction and wavelength were obtained. From the propagation characteristics of these waves, the water depth was estimated from the dispersion relationship. As a result of applying it to the data acquired in the Niigata coast, it was found out that in the shallow sea area, though the water depth could be analyzed with high accuracy, the measurement accuracy greatly lowered as the water depth deepened.