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基于张量表示的多时相极化SAR农作物分类方法*

许璐1,2, 张红1,2,†, 王超1,2,3, 吴樊1,2, 张波1,2, 汤益先1,2   

  1. 1 中国科学院空天信息创新研究院数字地球重点实验室,北京 100094;
    2 可持续发展大数据研究中心,北京 100094;
    3 中国科学院大学 北京 100049
  • 收稿日期:2023-11-07 修回日期:2024-01-17 发布日期:2024-01-25
  • 通讯作者: †张红 zhanghong@radi.ac.cn
  • 基金资助:
    *国家自然科学基金(42001278,41971395,41930110)

Multitemporal polarimetric SAR crop classification method based on tensor representation

XU Lu1,2, ZHANG Hong1,2,†, WANG Chao1,2,3, WU Fan1,2, ZHANG Bo1,2, TANG Yixian1,2   

  1. 1 Key Laboratory of Digital Earth Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing 100094, China;
    2 The International Research Center of Big Data for Sustainable Development Goals, Beijing 100094, China;
    3 University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2023-11-07 Revised:2024-01-17 Published:2024-01-25

摘要: 多时相极化合成孔径雷达(synthetic aperture radar, SAR)提供了丰富的极化散射信息,对不同类型的农作物监测具有重要的应用价值。为了充分利用多时相极化SAR数据的时间相关性和散射特征,本文提出一个多时相极化SAR分类方法,该方法基于完整的极化协方差矩阵,能够在张量空间保持协方差矩阵的复数矩阵结构、实现时间维度的独立表示,可同时适用于全极化和简缩极化SAR。该方法采用目标级的分类策略,首先,通过简单线性迭代聚类(simple linear iterative cluster,SLIC)方法实现多时相极化SAR的超像素联合分割;随后,将目标的极化协方差矩阵表示为张量的形式,利用张量域的多线性主成分分析(multilinear principle component analysis, MPCA)方法,实现多时相极化协方差矩阵的特征降维;最后,用决策树方法实现农作物分类。本文获取了4景RADARSAT-2 Fine Quad模式全极化SAR图像,对天津市武清区农作物种植区开展作物分类实验,相较于其他文献提出的方法,本文提出的方法取得了最高的总体分类精度。进一步,将本文方法推广至π/4模式和CTLR模式的简缩极化SAR,并将其农作物分类精度与全极化SAR进行对比,以研究不同极化SAR数据对作物的识别能力。实验结果表明,简缩极化SAR可以取得与全极化SAR相当的总体分类精度,但全极化SAR在水稻、荷花等小样本地物上表现更优。

关键词: 合成孔径雷达 (SAR), 全极化 (FP), 简缩极化 (CP), 农作物分类, 张量, 多线性主成分分析 (MPCA)

Abstract: Multitemporal polarimetric synthetic aperture radar (SAR) provides abundant polarimetric scattering information, which is of great value to the long-term monitoring of various crop lands. To make full use of the time correlation and polarimetric information of multitemporal polarimetric SAR, this paper proposed a multitemporal polarimetric SAR crop classification method, which is based on the complete polarimetric covariance matrix. The method can maintain the complex matrix structure of covariance matrix and realize the independent representation of time dimension in tensor space, so that it can be applied to both full- and compact-polarimetric SAR. The method adopted the object-level classification strategy. Firstly, the superpixel segmentation of multitemporal SAR data was achieved by the simple linear iterative clustering (SLIC) method. Then, the covariance matrices of multitemporal SAR were expressed as tensors, and the multilinear principal component analysis (MPCA) method was used to reduce the feature dimension. Finally, the crop classification is achieved by decision tree. In this research, four multitemporal RADARSAT-2 Fine Quad SAR images covered Wuqing district of Tianjin were used for the crop classification experiments. Compared with methods proposed in other references, the method proposed in this paper achieved the highest overall classification accuracy. Besides, the proposed method was applied to the π/4 mode and the CTLR mode compact-polarimetric SAR to discuss the capability of different kinds of polarimetric SAR in crop classification. Compared with the full-polarimetric SAR, the compact-polarimetric SAR could achieve comparable classification accuracies, but the full-polarimetric SAR performed better at the classes with small sample size, such as rice and lotus.

Key words: synthetic aperture radar (SAR), full polarimetric (FP), compact polarimetric (CP), crop classification, tensor, multilinear principal component analysis (MPCA)

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