Extraction of coastal ocean wave characteristics using remote sensing and computer vision technologies

Abstract

The coastal zone occurs at the interface of three major natural systems. These systems include the atmosphere, the ocean and the land surface. Ocean waves are among the most important forces shaping the world¿s coastlines. They drive environmental processes and human activity that occur within the coastal zone as well as on the open ocean. The assessment of wave characteristics, such as wave direction, wavelength, wave period and wave velocity, is critical to understanding coastal processes as baseline for better coastal management. However, monitoring and assessment of wave characteristics is challenging, given the high complexity of the ocean dynamics and large spatial extent. Traditionally, wave observation instruments such as wave buoys, wave poles, pressure transducers, inverted echo-sounders and current meters have been used to record ocean wave characteristics. Although delivering very accurate measurements, they only record punctual data. The work presented here is assessing whether optical imagery from the RapidEye satellite can be used to extract ocean wave characteristics such as wave direction, wavelength, wave period and wave velocity. If successful, the advantage of the proposed remote sensing-based approach would be the spatially continuous provision of wave characteristics for large areas, including the near-shore in a very cost-effective way.. As ground truth data for validating open ocean wave conditions are sparse, a lab test with simulated, controlled wave conditions was conducted to assess various approaches for the extraction of wave characteristics from remote sensing imagery. The techniques identified and developed under lab conditions are to be tested using RapidEye imagery on two study areas on the South African coast. Results are expected to significantly contribute to a more comprehensive understanding and monitoring of waves dynamics for better coastal planning.