Preliminary Study On Anomaly Model Of Regional Seawater Velocity Of Sound

In the "Tenth Five-Year" period, under the support of the National 863 Program, Chinese Academic of Surveying and Mapping and the China Shipbuilding Industry Corporation successfully developed the first set of underwater GPS system. And in the "Eleventh Five-Year" period, the two units completed the key technology of high-precision positioning of underwater multi-target together. On this basis, Chinese Academic of Surveying and Mapping proposed to establish the model of global sea water sound velocity field for precise positioning underwater. Acoustic signal is the basic measurement signal of acoustic positioning, acoustic propagation speed is seen as known data in underwater acoustic positioning system, so if there's error in the sound speed, it will lead to errors in distance measurement and the positioning results will appear system errors, and even cause positioning failure. Meanwhile, the existence of gradient in ocean sound speed makes the voice line bent, if not accurately determined, we can not determine the voice line accurately. Therefore, the ocean velocity of sound is the key issues in high precision underwater positioning. As stratification is existed in ocean velocity of sound, the general positioning work uses the average ocean velocity of sound, and how to fit a function of seawater velocity model is the key of precise positioning.In this paper, we did the following work:1. Seawater velocity modelRegional water velocity can be expressed as a function of seawater temperature, salinity, pressure, got the regional velocity model through the establishment of regional standard temperature model and interpolation of the salinity in global sea surface. A kind of vertical gradient function of salinity was fitted.2. Argo buoy data extractionArgo data is currently grown at the rate of 100,000 files every year, how to extract the massive information in data file is an important technology. The problems of global flow of ocean surface and the flow speed were researched through extracting the information of Argo buoy.3. Function fitting of vertical velocity gradient Using Argo buoy data, obtained the actual vertical velocity gradient of the sea through the empirical formula of sound speed. And the author compared the results with each empirical formula. Got the function by interpolation of velocity gradient using cubic spline interpolation and analyzed the accuracy of the interpolation function.