Study Of Sea Wave And Tide Measurements Based On GPS Velocity Estimation

As an important phenomenon of the sea, waves and tidal movement have a huge impact on human activities and coastal activities at sea. So far, there have been a variety of methods and instruments for waves and tide measurements. Although the existing methods can effectively measure the waves and tide, the disadvantages are also obvious. Visual method and optical method can not meet the bad weather and night observation of the requirements. Gravity, acoustic and pressure-type wave measurement equipments generally are more expensive, and an additional GPS receiver is needed to offer its position. Traditional tidal measurement techniques are required to carry out at the known point, so it is limited by the location. GPS has all-weather, high precision, simple, cheap and many other advantages. Based on the velocity vector from GPS Doppler measurements on the ship or buoy, the wave instantaneous variation can be obtained after the integral performance. Combined with spectral analysis method, the mean wave height, mean period and other parameters can be extracted. At the same time, the tidal information is also obtained. Compared to traditional tide measurement, GPS is more convenient and effective.Using GPS velocity measurement, we can obtain information of wave and tidal. The precision of absolute velocity measurement using raw Doppler is 3-15cm/s. So the velocity should be re-calculated using Doppler values derived from carrier phase observation. The data sampling rate is high enough to reach 1-2cm/s velocity accuracy. This article firstly describes the principles and methods of GPS absolute velocity determination, and then analyzes the accuracy of existing measurement methods. Thirdly, the GPS absolute velocity measurement method is introduced to measure the waves and tide, and extract the mean wave height, mean period and tide changes through the spectral analysis method. The results show, the correlation coefficient is as high as 0.98 with -1.6cm average error between GPS tide measurement and tide gauge results, the difference of GPS measurement of waves and wave gauges on the results just is 5cm, period difference is 0.7s.