Incidence Angle Normalization of Dual-Polarized Sentinel-1 Backscatter Data on Greenland Ice Sheet
Incidence Angle Normalization of Dual-Polarized Sentinel-1 Backscatter Data on Greenland Ice Sheet
复制标题
格陵兰冰盖上双偏振 Sentinel-1 反向散射数据的入射角归一化
DOI：
10.3390/rs14215534
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发表时间：
2022-11
期刊：
影响因子：
5
通讯作者：
Xiao Cheng
中科院分区：
文献类型：
--
作者：
Xiao Chen;Gang Li;Zhuoqi Chen;Qi Ju;Xiao Cheng
合成孔径雷达（SAR）图像观测格陵兰冰盖（GrIS）的后向散射系数是入射角相关的，这阻碍了后续的应用，如监测其表面融化。因此，具有不同入射角的后向散射强度应该被归一化。本研究提出了一种双偏振Sentinel-1图像GrIS的入射角归一化方法。使用后向散射系数差与准同时观察到的上升和下降图像对的入射角差之间的比率来训练多元线性回归模型。回归因素包括地理位置和海拔高度。对上升和下降图像的精度评估表明，对于水平发射和水平接收（HH）图像，归一化结果比广泛使用的余弦平方校正方法更好，对于水平发射和垂直接收（HV）图像，归一化结果略有改善。另一个数据集的GrIS哨兵-1镶嵌在2020年的四个6天的重复周期也进行了测试，以评估所提出的方法，并产生类似的结果。对于HH图像，所提出的方法比余弦平方方法表现更好，平均降低0.34 dB RMSE。我们提出的方法的整体精度分别为0.77和0.75 dB的HH和HV图像。所提出的入射角归一化方法有利于宽测绘带SAR图像在GrIS大尺度、长周期观测研究中的应用。
The backscatter coefficients of Synthetic Aperture Radar (SAR) images that observe the Greenland Ice Sheet (GrIS) are incidence angle dependent, which impedes subsequent applications, such as monitoring its surface melting. Therefore, backscatter intensities with varying incidence angles should be normalized. This study proposes an incidence angle normalization method for dual-polarized Sentinel-1 images for GrIS. A multiple linear regression model is trained using the ratio between the backscatter coefficient differences and the incidence angle differences of quasi-simultaneously observed ascending and descending image pairs. Regression factors include the geographical position and elevation. The precision evaluation to the ascending and descending images suggests better normalization results than the widely used cosine-square correction method for horizontal transmit and horizontal receive (HH) images and a slight improvement for horizontal transmit and vertical receive (HV) images. Another dataset of GrIS Sentinel-1 mosaics in four 6-day repeating periods in 2020 is also tested to evaluate the proposed method and yields similar results. For HH images, the proposed method performs better than the cosine-square method, reducing 0.34 dB RMSE on average. The overall accuracy of our proposed method is 0.77 and 0.75 dB for HH and HV images, respectively. The proposed incidence angle normalization method can benefit the application of wide-swath SAR images to the study of large-scale and long-period observation on GrIS.