An upgraded submerged Doppler-type directional wave meter can measure 10 wave quantities related to directional wave motions, i.e. water surface elevation, 3 components of water particle velocities at each layer of 3 different water depth ranging from shallow to deep. As a result, accuracy improvement is generally confirmed in various wave conditions when all the quantities are applied to the estimations, compared with the cases where conventional 4 wave quantities are applied to the estimations. Moreover, the advantage of BDM with the improved computation method was confirmed.
From the viewpoints of various activities in the coastal region such as development, utilization and disaster prevention, the ocean wave is the most variable or important external natural force. Therefore, at many coastal sites throughout Japan, observation and examination of ocean waves are continuously conducted using established information networks including the Nationwide Ocean Wave information network for Ports and HArbourS (NOWPHAS). Desirable wave observation should include comprehensive measurements performed simultaneously and at the same point, covering not only the wave height and wave period but also mutually closely-related wave quantities such as the wave direction, current and tidal level. However, when actually observing multiple oceanographic phenomena, operating conditions of measuring instruments and environments often make it difficult to perform simultaneous and long-term observation of multiple wave quantities at the same point. With these backgrounds, the directional wave meter has been developed to "standardize the wave direction measurement", and about 80 sites along Japanese coastal areas are now equipped with this system. As more observation sites are equipped with the directorial wave meters, a wider range of users are now provided with high-accuracy directional spectra, which used to be available only by using an array of wave height meters or large-scale wave observation system.
