极化相干层析反演森林垂直结构原理与方法研究

Principle and Method of Forest Vertical Structure Inversion Using Polarization Coherence Tomography

层析技术对于垂直结构信息提取具有独特的优势,已被广泛应用于森林垂直结构参数提取、混合环境分离等。极化相干层析(Polarization Coherence Tomography,PCT)是一种依靠先验知识基于干涉复相干通过傅立叶—勒让德展开式重建目标垂直结构的层析技术。单基线或双基线PCT技术依然可以获取森林垂直结构剖面,由于基线数量过少,很多学者对这一方法存在质疑。研究目的是分析单基线PCT技术提取森林垂直结构剖面的原理、方法与目前存在的问题。具体方法如下:①应用森林模拟数据提取不同森林场景平均后向散射能量垂直分布;②采用PCT技术获取模拟场景尺度森林垂直结构剖面(相对反射率垂直分布);③分析平均后向散射能量垂直分布与森林垂直结构剖面的异同;④总结森林垂直结构剖面含义及物理意义。结果表明:PCT技术重建的森林垂直结构剖面能够近似表征平均后向散射能量垂直分布轮廓;不同极化方式其森林垂直结构剖面与平均后向散射能量垂直分布也不同;平均后向散射能量垂直分布包含更多的细节信息。

Tomographic technology has unique advantage in forest vertical structure information extraction, and it has been applied for forest vertical structure parameters extraction,hybrid environment separation and so on.Polarization Coherence Tomography(PCT)is a tomography technique relying on a priori information using Fourier-Legendre series to reconstruct target vertical structure based on interferometric coherence.Single or dual-baseline PCT technique still can be used for forest vertical structure profile extraction.Some scholars questioned this method as it has too little baselines to get vertical structure information.The objective of our research is to analyze the principle,approach and present problems of forest vertical structure profile extraction using single baseline PCT technology.Specific method is as follows:first, vertical distribution of mean backscattering power in different forest scenarios are collected using forest simulation data;second,forest vertical structure profile(vertical distribution of relative reflectivity)is produced by PCT;third,similarities and differences between vertical distribution of mean backscattering power and forest vertical structure profile are analyzed;fourth,physical significance of forest vertical structure profile will be concluded.The results show that:①Forest vertical structure profile reconstructed by PCT approximately express the vertical distribution outline of mean backscattering power.②Forest vertical structure profile and mean backscattering power vertical distribution of different polarization are different. ③The vertical distribution of mean backscattering power contains more details.