College of Engineering, Nanjing Agricultural University, Nanjing 210031, China.
National Engineering and Technology Center for Information Agriculture, Nanjing 210095, China.
Sensors (Basel). 2020 Mar 25;20(7):1830. doi: 10.3390/s20071830.
A coefficient , which was defined as the ratio of NIR (near infrared) to the red reflected spectral response of the spectrometer, with a standard whiteboard as the measuring object, was introduced to establish a method for calculating height-independent vegetation indices (VIs). Two criteria for designing the spectrometer based on an active light source were proposed to keep constant. A designed spectrometer, which was equipped with an active light source, adopting 730 and 810 nm as the central wavelength of detection wavebands, was used to test the Normalized Difference Vegetation Index (NDVI) and Ratio Vegetation Index (RVI) in wheat fields with two nitrogen application rate levels (NARLs). Twenty test points were selected in each kind of field. Five measuring heights (65, 75, 85, 95, and 105 cm) were set for each test point. The mean and standard deviation of the coefficient of variation (CV) for NDVI in each test point were 3.85% and 1.39% respectively, the corresponding results for RVI were 2.93% and 1.09%. ANOVA showed the measured VIs possessed a significant ability to discriminate the NARLs and had no obvious correlation with the measurement heights. The experimental results verified the feasibility and validity of the method for measuring height-independent VIs.
引入了一个系数，它定义为近红外（NIR）与光谱仪红色反射光谱响应的比值，以标准白板作为测量对象，建立了一种计算与高度无关的植被指数（VIs）的方法。提出了基于主动光源设计光谱仪的两个标准，以保持 不变。设计了一种配备主动光源的光谱仪，采用 730nm 和 810nm 作为检测波段的中心波长，用于测试两种氮施用量水平（NARLs）下麦田的归一化差异植被指数（NDVI）和比值植被指数（RVI）。在每种田间选择了 20 个测试点。每个测试点设置了五个测量高度（65、75、85、95 和 105cm）。每个测试点的 NDVI 的变异系数（CV）的平均值和标准差分别为 3.85%和 1.39%，RVI 的相应结果为 2.93%和 1.09%。方差分析表明，所测量的 VIs 具有显著区分 NARLs 的能力，与测量高度没有明显的相关性。实验结果验证了测量与高度无关的 VIs 的方法的可行性和有效性。
