JP4725883B2 - Conversion method from water pressure wave to surface wave - Google Patents

Description

The present invention relates to a wave height meter for detecting a wave height.

A generally used ultrasonic wave height meter is installed on the seabed and measures the distance to the sea surface with ultrasonic waves. However, when waves break due to strong winds, bubbles are generated in the sea, causing a phenomenon that cannot be measured correctly. In this case, the water pressure wave obtained with the built-in water pressure gauge is converted into a surface wave with a digital filter, and the wave height is calculated (for example, refer to Patent Document 1). The frequency characteristic of the digital filter used for this is generally one having a certain frequency characteristic. In this way, practical wave heights are almost always obtained. However, sometimes there are cases where the wave heights vary greatly. This is because it is treated as linear even in a frequency region where the water pressure data is nonlinear.
Japanese Patent Laid-Open No. 10-141953 “Measuring tide level”, Coastal Development Technology Center, 2002, p. 145

In general, when the wave height is large, the waves break and the ultrasonic method cannot be used, and water pressure waves are often used. For this reason, wave height measurement by water pressure waves is important. For this reason, it is necessary to always output the correct wave height even when observing the wave height using water pressure waves. The problem to be solved is to avoid the inaccurate wave height conversion that appears occasionally.

Generally, the wave height is calculated by processing 20 minutes of data.
Even in the case of breaking the waves during these 20 minutes, there are places where the ultrasonic waveform is normally measured. The above-mentioned problem can be solved by converting the water pressure wave into the surface wave so that the waveform of the ultrasonic wave in the normal part and the surface wave obtained by converting from the water pressure wave coincide well. That is, the digital filter is determined so that the normal ultrasonic waveform and the water pressure wave converted surface wave coincide with each other, and the water pressure wave is converted into the surface wave using the determined digital filter.

The implementation of the present invention is carried out using wave height meter data by an ultrasonic wave height meter and a water pressure meter, a computer and software. The software has the following features: (1) Waveform comparison function such as superimposing the wave height waveform by ultrasonic waves and surface wave data converted from water pressure waves, and (2) Digital filter characteristics to convert from water pressure waves to surface waves. (3) A function that can be varied, (3) a function that converts water pressure waves into surface waves using the characteristics of a digital filter, and a function that can repeat these three functions and perform trial and error.

First, a water pressure wave conversion surface wave that has passed through a standard pressure surface wave conversion filter is calculated, and the ultrasonic wave waveform is superimposed and displayed. Next, in the display, a place where the ultrasonic waveform is correctly measured is searched for and compared with the water pressure wave converted surface wave. If they do not match, move to the digital filter characteristic setting screen, determine the maximum correction magnification and conversion maximum frequency, and calculate the hydraulic wave conversion surface wave again with the digital filter having the characteristic. Then, again, the ultrasonic waveform is superimposed and displayed, and the above-described procedure is repeated. In this way, the digital filter characteristics are determined so that the ultrasonic waveform and the water pressure wave converted surface wave are best matched at the place where the ultrasonic waveform is correctly measured. Next, a surface wave is calculated from the water pressure wave with the digital filter having the determined digital filter characteristics to obtain a wave height waveform.

By this invention, the peak value by a hydraulic wave height meter becomes accurate in all cases.
Moreover, although it is a part, since the degree of coincidence with the wave height waveform by the ultrasonic wave can be shown, the validity of the conversion can be shown.

There are two types of wave height meters, generally called cable types, and direct recording type wave height meters. The former connects a wave height meter and a land facility with a cable, and can acquire waveform data in real time. The latter has a memory to record data in the wave height meter. It is installed and collected on the seabed for several months, and the wave height during the installation is calculated from the collected memory data. It is to be measured.

In general, real-time wave height may or may not be required.
In an embodiment in which real-time wave height is required, the computer determines and analyzes the digital filter characteristics described above. As an embodiment in which real-time wave height is not required, a person performs the above-described determination of the digital filter characteristics and analyzes it. That is, as an embodiment, there are roughly two ways of implementation. One is a case where a computer performs this trial and error, and the other is a case where a human performs it.

Claims (3)

  When an ultrasonic wave height meter with a water pressure sensor is used to determine the surface wave waveform converted from the water pressure wave, the surface wave waveform measured by the ultrasonic wave is disrupted. Waveform comparison function that displays the waveform and the surface wave waveform converted from the water pressure wave, the function that converts the water pressure wave to the surface wave by the digital filter, and the maximum correction magnification of the digital filter that converts the water pressure wave to the surface wave With the function that can change the maximum conversion frequency, change the maximum correction magnification or the conversion maximum frequency or the maximum correction magnification and the conversion maximum frequency, and repeatedly use each function by trial and error, and the surface wave measured by ultrasonic Optimum maximum correction magnification by visually judging the coincidence of the amplitude of the two waveforms of the surface wave converted from the water pressure wave in a synchronized and similar part Seeking conversion maximum frequency, method of converting the pressure waves into surface waves. A wave height meter using a technique for converting a water pressure wave as defined in claim 1 into a surface wave. Wave height analysis software using a technique for converting a water pressure wave as defined in claim 1 into a surface wave.