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Optimizing LUT-based inversion of leaf chlorophyll from hyperspectral lidar data: Role of cost functions and regulation strategies
International Journal of Applied Earth Observation and Geoinformation ( IF 7.6 ) Pub Date : 2021-10-22 , DOI: 10.1016/j.jag.2021.102602
Jia Sun 1, 2 , Shuo Shi 3 , Lunche Wang 1 , Haiyan Li 4 , Shaoqiang Wang 1 , Wei Gong 3 , Torbern Tagesson 2, 5
Affiliation  

Hyperspectral lidar (HSL) is a novel remote sensing technology that provides spectral information in addition to spatial features. This unprecedented data source leads to new possibilities for monitoring leaf biochemistry. Inversion of physically based radiative transfer models (RTMs) is a popular method for deriving leaf physiological traits due to its robustness and generalization capability. However, owing to the active nature of the HSL system, RTM inversion using the backscattered reflectance spectra may face new problems. Thus, optimization strategies for RTM inversion based on HSL measurements need to be studied. In this paper, several regulation strategies for lookup table (LUT)-based PROSPECT model inversions were explored for an HSL system. In particular, the influences of i) different cost functions, ii) multiple best solutions (1–1000), iii) different LUT sizes (100–100000), and iv) spectral domains for leaf chlorophyll (Chl) retrieval were analyzed. An evaluation against an experimental dataset of rice leaves indicated that i) least-squares estimation (LSE) provided better estimates than seven alternative cost functions when more than 200 solutions were taken; ii) accuracy in leaf Chl retrieval increased up until 200 solutions where after it stabilized; iii) the impact of LUT size became insignificant after 1000; and iv) the red edge was the spectral domain that had the largest impact on the inversion performance. The optimal performance of leaf Chl estimation reached R2 of 0.58 and RMSE of 0.69 between the z-scores from retrieved and measured leaf Chl. The practical application of combining RTM with HSL data will facilitate the detection of leaf-level biochemistry and advance research on terrestrial carbon cycle modeling.



中文翻译:

从高光谱激光雷达数据中优化基于 LUT 的叶绿素反演:成本函数和调节策略的作用

高光谱激光雷达 (HSL) 是一种新颖的遥感技术,除了提供空间特征之外,还提供光谱信息。这种前所未有的数据源为监测叶片生物化学带来了新的可能性。基于物理的辐射传输模型 (RTM) 的反演因其稳健性和泛化能力而成为推导叶片生理特征的流行方法。然而,由于 HSL 系统的主动性质,使用反向散射反射光谱的 RTM 反演可能面临新的问题。因此,需要研究基于 HSL 测量的 RTM 反演优化策略。在本文中,针对 HSL 系统探索了基于查找表 (LUT) 的 PROSPECT 模型反演的几种调节策略。特别是,i)不同成本函数,ii)多个最佳解决方案(1-1000)的影响,iii) 分析了不同 LUT 大小 (100–100000) 和 iv) 用于叶绿素 (Chl) 检索的光谱域。对水稻叶片实验数据集的评估表明,i) 最小二乘估计 (LSE) 在采用 200 多个解决方案时比七个替代成本函数提供了更好的估计;ii) 叶 Chl 检索的准确性增加到 200 个解决方案,然后稳定;iii) LUT 大小的影响在 1000 之后变得不显着;iv) 红色边缘是对反演性能影响最大的谱域。叶 Chl 估计的最佳性能达到 R 对水稻叶片实验数据集的评估表明,i) 最小二乘估计 (LSE) 在采用 200 多个解决方案时比七个替代成本函数提供了更好的估计;ii) 叶 Chl 检索的准确性增加到 200 个解决方案,然后稳定;iii) LUT 大小的影响在 1000 之后变得不显着;iv) 红色边缘是对反演性能影响最大的谱域。叶 Chl 估计的最佳性能达到 R 对水稻叶片实验数据集的评估表明,i) 最小二乘估计 (LSE) 在采用 200 多个解决方案时比七个替代成本函数提供了更好的估计;ii) 叶 Chl 检索的准确性增加到 200 个解决方案,然后稳定;iii) LUT 大小的影响在 1000 之后变得不显着;iv) 红色边缘是对反演性能影响最大的谱域。叶 Chl 估计的最佳性能达到 R iv) 红色边缘是对反演性能影响最大的谱域。叶 Chl 估计的最佳性能达到 R iv) 红色边缘是对反演性能影响最大的谱域。叶 Chl 估计的最佳性能达到 R2 of 0.58 和 RMSE of 0.69 从检索和测量的叶 Chl 的 z 分数之间。将 RTM 与 HSL 数据相结合的实际应用将有助于检测叶级生物化学并推进陆地碳循环模型的研究。

更新日期:2021-10-25
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