The scatterometer onboard the China-France Oceanography Satellite (CFOSAT) is the first rotating fan beam scatterometer (CSCAT) in operation. It is used to measure the ocean surface wind fields over a large observation swath. Geolocation is an important part of the preprocessing of scatterometer data. The accuracy of geolocation has a large impact on the accuracy of wind field retrieval. It is necessary to estimate and analyze the geolocation processing of CSCAT. The challenge is understanding how to estimate the geolocation errors of CSCAT. In this study, the coastline inflection method is used to estimate the geolocation errors of CSCAT based on the distribution characteristics of the backscatter coefficients at both the ocean and the land. The coastline inflection points are obtained using the gradient changes of backscatter coefficients near the coastline. The locations of these points are in line with the trend of the high-precision coastline data. The geolocation errors are estimated by comparing these points with the high-precision coastline. The results show that the current geolocation errors of CSCAT are about 7.31 km, which meets the requirements of 25 × 25 km wind field retrieval. In addition, because the geolocation of scatterometer data is affected by terrain, the geolocation errors of CSCAT are corrected based on an elevation correction algorithm using high-precision digital elevation model data. The results verify the effectiveness of the algorithm.

中文翻译：

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利用海岸线后向散射系数估计和校正CFOSAT散射计的地理定位误差

中法海洋卫星（CFOSAT）搭载的散射仪是第一个运行的旋转扇形光束散射仪（CSCAT）。它用于测量大观测带上的海面风场。地理定位是散射仪数据预处理的重要组成部分。地理定位的准确性对风场反演的准确性有很大影响。有必要对CSCAT的地理定位处理进行估计和分析。挑战在于了解如何估计 CSCAT 的地理定位误差。本研究基于海洋和陆地的后向散射系数分布特征，采用海岸线拐点法估计CSCAT的地理定位误差。利用海岸线附近后向散射系数的梯度变化得到海岸线拐点。这些点的位置符合高精度海岸线数据的趋势。通过将这些点与高精度海岸线进行比较来估计地理定位误差。结果表明，目前CSCAT定位误差约为7.31 km，满足25×25 km风场反演的要求。此外，由于散射仪数据的地理定位受地形影响，CSCAT的地理定位误差采用高精度数字高程模型数据基于高程校正算法进行校正。结果验证了算法的有效性。通过将这些点与高精度海岸线进行比较来估计地理定位误差。结果表明，目前CSCAT定位误差约为7.31 km，满足25×25 km风场反演的要求。此外，由于散射仪数据的地理定位受地形影响，CSCAT的地理定位误差采用高精度数字高程模型数据基于高程校正算法进行校正。结果验证了算法的有效性。通过将这些点与高精度海岸线进行比较来估计地理定位误差。结果表明，目前CSCAT定位误差约为7.31 km，满足25×25 km风场反演的要求。此外，由于散射仪数据的地理定位受地形影响，CSCAT的地理定位误差采用高精度数字高程模型数据基于高程校正算法进行校正。结果验证了算法的有效性。使用高精度数字高程模型数据，基于高程校正算法对 CSCAT 的地理定位误差进行校正。结果验证了算法的有效性。使用高精度数字高程模型数据，基于高程校正算法对 CSCAT 的地理定位误差进行校正。结果验证了算法的有效性。