Evaluation of Wave Propagation Characteristics Using Oblique Uav Video Images

Abstract

The camera mounted on unmanned Aerial Vehicles (UAVs) for sea surface evaluation has recently attracted attention because it is flexible for moving and easy to use. However, it is known that the absence of measurement occurs when image quality is strongly affected by sun glitter. In this study, we develop a method to evaluate wave propagation from different oblique aerial video images. Ortho-images were created from video frames by using the collinearity equation and perspective transform. Time-averaged images were created by the average of frames during the time after that the grayscale images were calculated. The relationship between the time-averaged grayscale image and light environment was investigated by considering the reflection properties of the sea surface and the radiance distribution of incident light. This model emphasized the best observation angle. The significant wave period and the wave celerity can be evaluated from the gray-scale images. The wave spectrum, wave direction, and long-component wavelength were handled by using 2D Fourier transform and low-pass filter. As a result, applying the present method to data acquired in the Tateyama coast, the wave propagation characteristic was successfully evaluated.

Giải pháp đo vận tốc sóng trên mặt sông bằng ảnh nghiêng từ máy ảnh thương mại

“…Phương pháp này cho phép người nghiên cứu có thể quan sát đường biển dọc theo đường bờ, từ đó có thể tính toán được độ sâu của khu vực rất gần bờ biển (Sun et al, 2019). Ngoài ra thiết bị bay cũng giúp đánh giá các đặc điểm thủy triều, sóng từ xa bờ ảnh hưởng đến đường bờ biển (Matsuba & Sato., 2018;Luu et. al., 2020).…”