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首页> 外文会议>Remote Sensing for Agriculture, Ecosystems, and Hydrology VIII >Comparison of different approaches to retrieve plant water content of summer barley canopies from spectroradiometric measurements
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Comparison of different approaches to retrieve plant water content of summer barley canopies from spectroradiometric measurements

机译：从光谱辐射测量中检索夏季大麦冠层植物水分含量的不同方法的比较

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摘要

Different empirical and physically based methods were employed to derive the vegetation water content of summer barley plots (n=22) from spectroradiometric measurements (ASD FieldSpec II). Data were acquired for two different phenological stages in May and June 2005. For the empirical approaches, a ratio index using the reflectances at 1355 and 710 nm and the partial least squares regression provided the best estimation results (r~2 > 0.90). Canopy radiative transfer modeling was performed by coupling the PROSPECT and SAIL models. The retrieved values for C_w (equivalent leaf water thickness) x LAI were highly correlated (r~2 = 0.86) with the measured canopy water contents, but showed distinct underestimates. For the vegetative phenological stage investigated in May, the PROSAIL results were very close to the measured water contents of the leaf fraction, but this was not valid for the data collected in June. Obviously, different phenological stages need specific model calibration, as the presence of undetectable water in non-leaf tissues is variable. All approaches were applied to synthetic HyMap data generated by resampling the spectroradiometer readings. Estimation results did not differ significantly; thus, by neglecting spatial scaling effects, the pure spectral information provided by both data sets is almost equivalent.
机译：采用不同的基于经验和物理的方法，通过光谱辐射测量（ASD FieldSpec II）得出夏季大麦田（n = 22）的植被含水量。在2005年5月和2005年6月两个不同的物候阶段获得了数据。对于经验方法，使用在1355和710 nm处的反射率和偏最小二乘回归的比率指数提供了最佳估计结果（r〜2> 0.90）。通过耦合PROSPECT模型和SAIL模型进行冠层辐射传递建模。 C_w（等效叶水厚度）x LAI的取回值与测得的冠层水含量高度相关（r〜2 = 0.86），但显示出明显的低估。在5月份进行的植物物候研究阶段，PROSAIL结果非常接近于测得的叶部分水分含量，但这对6月份收集的数据无效。显然，不同的物候阶段需要特定的模型校准，因为非叶组织中无法检测到的水的存在是可变的。所有方法均应用于通过对光谱辐射计读数进行重新采样而生成的合成HyMap数据。估计结果没有显着差异；因此，通过忽略空间缩放效应，两个数据集提供的纯光谱信息几乎相等。

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