Assessment of the Hotspot Effect for the PROSAIL Model With POLDER Hotspot Observations Based on the Hotspot-Enhanced Kernel-Driven BRDF Model
Assessment of the Hotspot Effect for the PROSAIL Model With POLDER Hotspot Observations Based on the Hotspot-Enhanced Kernel-Driven BRDF Model
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基于热点增强核驱动的 BRDF 模型通过 POLDER 热点观测评估 PROSAIL 模型的热点效应
DOI：
10.1109/tgrs.2019.2917923
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发表时间：
2019
影响因子：
8.2
通讯作者：
Guo Jing
中科院分区：
文献类型：
--
作者：
Dong Yadong;Jiao Ziti;Cui Lei;Zhang Hu;Zhang Xiaoning;Yin Siyang;Ding Anxin;Chang Yaxuan;Xie Rui;Guo Jing
热点效应是植被冠层的一种典型角反射特征，它包含着植被结构参数反演的重要信息。迄今为止，各种解析双向反射分布函数（BRDF）模型（例如，由于缺乏精确的热点测量（对于现场测量）或适当的方法（对于机载和星载测量），PROSAIL模型）很少通过具有足够热点观测的多角度测量进行评估。在本文中，我们开发了一种方法，以进一步改善核驱动模型的热点效应，并设计了一个框架，利用改进的核驱动模型作为桥梁，评估的PROSAIL模式的热点效应与偏振和方向性的地球反射率（POLDER）热点观测。结果表明，该方法进一步提高了模型和热点方向附近的观测值之间的拟合，特别是在几何光学散射分量控制目标反射率的罕见情况下。此外，PROSAIL多角度数据所指示的热点签名显示出比POLDER观测更大的可变性。改进的核驱动模型中的$C {1}$和$C {2}$可以作为基准参数，用于量化物理模型多角度模拟数据的热点效应的幅度和宽度，从而为评估和分析物理模型的热点效应提供了可能性，进而有助于从热点特征中反演植被冠层的结构参数。
The hotspot effect is a typical angular reflectance signature of vegetation canopies and contains important information for the retrieval of vegetation structural parameters. To date, the hotspot effect of various analytical bidirectional reflectance distribution function (BRDF) models (e.g., the PROSAIL model) has rarely been assessed by multiangular measurements with sufficient hotspot observations due to the lack of accurate hotspot measurements (for field measurements) or appropriate methods (for airborne and spaceborne measurements). In this paper, we develop a method to further improve the hotspot effect of the kernel-driven model and design a framework to utilize the improved kernel-driven model as a bridge to assess the hotspot effect of the PROSAIL model with Polarization and Directionality of the Earth Reflectance (POLDER) hotspot observations. The results indicate that the proposed method further improves the fits between the models and the observations in the vicinity of the hotspot direction, particularly in the rare situations where the geometric-optical scattering component governs the target reflectance. In addition, the hotspot signature indicated by the PROSAIL multiangular data shows a larger variability than that of POLDER observations. $C_{1}$ and $C_{2}$ in the improved kernel-driven model can be used as benchmarked parameters to qualify the amplitude and width of the hotspot effect for the simulated multiangular data of physical BRDF models and thus present the potential for the assessment and analysis of the hotspot effect of physical models, which, in return, helps retrieve the structural parameters of vegetation canopies from hotspot signatures.