發(fā)布時間：2018-04-20 03:05

  本文選題：海表面流場 + SAR順軌干涉　； 參考：《國家海洋環(huán)境預報中心》2017年碩士論文

【摘要】：海流是海洋科學研究中最基本的要素,也是海水的重要運動形式之一。海流研究對海洋減災、海上搜救、海岸帶建設、漁業(yè)、航運、污染物擴散等都有重要的研究意義。合成孔徑雷達(Synthetic Aperture Radar,SAR)順軌干涉(Along-Track Interferometric,ATI)具有全天時、全天候、寬測繪帶、高分辨率的優(yōu)點,可以獲取大面積、高分辨率、高精度的海洋表面流速信息。一個理想的SAR順軌干涉系統(tǒng)是進行海流反演的基礎,本文以高分三號衛(wèi)星(GF-3)標準條帶模式為例,分析影響SAR順軌干涉海表面流場測量精度的因素,通過仿真對極化方式、入射角、順軌干涉有效基線、噪聲等效后向散射系數進行了研究,給出了適用于海表面流速測量的理想系統(tǒng)參數,指出高分三號衛(wèi)星在VV極化、35°~45°入射角、NESZ優(yōu)于-20dB的情況下適合進行流場測量。針對單星基線過短不能很好的進行流場測量的問題,分析了雙星編隊模式下理想的順軌干涉有效基線,結果表明,高分三號衛(wèi)星在順軌干涉有效基線范圍為28m~56 m時能取得較好的觀測結果,仿真結果為后續(xù)衛(wèi)星編隊海流監(jiān)測系統(tǒng)的設計提供了參考。其次,利用GF-3衛(wèi)星的ATI模式數據對干涉處理獲得相位圖的過程進行了演示,主要處理步驟包括:SLC數據的讀取與顯示、利用復相關系數進行主輔圖像的配準、將兩幅圖像進行干涉處理獲得干涉相位圖、利用圓周期均值濾波對干涉相位圖進行降噪處理、分析了獲得0.1m/s測速精度所需的多視數并使用多視處理降低相干斑噪聲、對纏繞相位進行解纏、對通道不平衡引起的非零干涉相位進行定標、對運動目標引起的方位向偏移進行校正。最后,根據系統(tǒng)參數的分析結果,利用理想的順軌干涉仿真數據進行一維海表面流場反演,首先對仿真數據進行一系列干涉處理得到可用的干涉相位圖,然后基于迭代反演算法進行海流反演,反演誤差在0.04m/s左右,驗證了算法的可行性。針對目前算法固定步長因子的問題,引入了自適應變步長因子進行改進,分別使用固定步長和變步長因子進行反演,結果表明使用變步長因子可以提高反演精度。
[Abstract]:Current is the most basic element in marine scientific research, and it is also one of the important forms of sea water movement. Current research is of great significance to marine disaster reduction, marine search and rescue, coastal zone construction, fisheries, shipping, pollutant diffusion and so on. Synthetic Aperture radar (SAR) along track interference (Along-Track Interferometric) has the advantages of all-day, all-weather, wide mapping band and high resolution. It can obtain large area, high resolution and high precision information of ocean surface velocity. An ideal SAR along orbit interference system is the basis for ocean current inversion. Taking the GF-3 standard strip model as an example, this paper analyzes the factors that affect the accuracy of the measurement of the current field on the sea surface of the SAR along the orbit interference, and makes a simulation of the polarization mode. The incident angle, the effective baseline of orbit interference, the equivalent backscatter coefficient of noise are studied, and the ideal system parameters for measuring the surface velocity of Yu Hai are given. It is pointed out that the Gaofen 3 satellite is suitable for flow field measurement under the condition that the incidence angle of VV polarization is 35 擄or 45 擄and the incidence angle of NESZ is better than -20 dB. Aiming at the problem that the single satellite baseline is too short to measure the flow field well, the ideal effective baseline of orbit interference in the two-star formation mode is analyzed. The results show that, Gaofen 3 satellite can obtain better observation results when the effective baseline range of orbit interference is 28m~56 m. The simulation results provide a reference for the design of the following satellite formation current monitoring system. Secondly, using the ATI mode data of GF-3 satellite, the process of obtaining phase map by interference processing is demonstrated. The main processing steps include reading and displaying the data of GF-3, and using the complex correlation coefficient to register the main and auxiliary images. The interference phase map is obtained by interferometric processing of two images, and the interference phase map is de-noised by circle periodic mean filter. The multi-view number needed to obtain the accuracy of 0.1m/s velocimetry is analyzed and the speckle noise is reduced by multi-view processing. Unwrapping the winding phase, calibrating the non-zero interference phase caused by channel unbalance, and correcting the azimuth offset caused by moving target. Finally, according to the analysis results of the system parameters, we use the ideal simulation data to retrieve the one-dimensional sea surface current field. Firstly, we use a series of interferometric processing to obtain the available interferometric phase map. Then the current inversion based on iterative inversion algorithm is carried out, and the inversion error is about 0.04m/s, which verifies the feasibility of the algorithm. In order to solve the problem of fixed step size factor, adaptive variable step factor is introduced to improve the inversion accuracy. The variable step size factor and the fixed step size factor are used for inversion, respectively. The results show that the variable step size factor can improve the inversion accuracy.
【學位授予單位】：國家海洋環(huán)境預報中心
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P715.6

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本文編號：1775939