Refined Doppler Centroid Estimation in Spaceborne SAR For Mapping Ocean Current Velocity

• Main Authors: Li-Nong Wang, 王立農
• Other Authors: Kun-Shan Chen
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/60032852448362348548

碩士 === 國立中央大學 === 太空科學研究所 === 99 === ADCP(Acoustic Doppler Current Profiler) is the most common method to obtain the ocean current information. However, in order to obtain sufficient spatial resolution of the current-data, it is rather expensive both in time and cost. Theoretically, it is possible to extract the surface target velocity from the Doppler shift embedded in SAR phase history in which the azimuth frequency shift is related to the motion of surface target in the radial direction. In this thesis, Correlation Doppler Estimation(CDE) was used to compute the baseband Doppler centroid by varying window size. The SAR data was acquired by ERS-2 satellite. It should be noted that the Doppler effects due to the satellite altitude variations and Earth rotation, among others, were correctly removed. By doing so, the Doppler shift is carefully checked against relative stationary ground surfaces which basically induce zero Doppler shift. The current velocity is then converted from Doppler shift. It is found that the CDE method is reasonably accurate over the homogeneous scene, like the ocean surface. The larger the window size we used, the lower the standard deviation is at cost of spatial resolution. Experimental results show that detection of the variations of current field using SAR is highly possible at relatively large scale observation.