Values for Doppler center frequency are calculated from the echo signal at the satellite using the Doppler centroid method and so include the predicted Doppler frequency caused by the relative motion of the satellite and the Earth,which is the main component of Doppler center frequency and must be removed to obtain the Doppler frequency anomaly for ocean current measurement.In this paper,a new Doppler frequency anomaly algorithm was proposed when measuring surface currents with synthetic aperture radar(SAR).The key of the proposed algorithm involved mean filtering method in the range direction and linear fitting in the azimuth direction to remove the radial and the azimuthal component of predicted Doppler frequency from the Doppler center frequency,respectively.The basis is that the theoretical Doppler center frequency model of SAR exhibits an approximately linear characteristic in both the range direction and in the azimuth direction.With the help of the new algorithm for predicted Doppler frequency removal,the estimation error of Doppler frequency anomaly can be reduced by avoiding employing the theoretical antenna pattern and imperfect satellite attitude parameters in the conventional Doppler frequency method.SAR measurement results demonstrated that,compared to the conventional Doppler frequency with/without error correction method,the proposed algorithm allows for a pronounced improvement in the current measuring accuracy in comparison with the global ocean multi-observation(MOB)products.In addition,the effectiveness and robustness of the proposed Doppler algorithm has been demonstrated by its application in the high velocity current in the Kuroshio region.

Lihua WANG;Yanghua GAO;Peng LU;Li FAN;Yunxuan ZHOU

Department of Geography and Spatial Information Techniques,Center for Land and Marine Spatial Utilization and Governance Research,Ningbo University,Ningbo 315211,China;Institute of East China Sea,Ningbo University,Ningbo 315211,China;Chongqing Institute of Meteorological Sciences,Chongqing 401147,China;College of Geo-Exploration Science and Technology,Jilin University,Changchun 130026,China;State Key Laboratory of Estuarine and Coastal Research,East China Normal University,Shanghai 200062,China

海洋湖沼学报（英文版）

[1]Lihua WANG;Yanghua GAO;Peng LU;Li FAN;Yunxuan ZHOU-.A new Doppler frequency anomaly algorithm for surface current measurement with SAR)[J].海洋湖沼学报（英文版）,2022(02):470-484

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