A new technique for extracting the red edge position from hyperspectral data: The linear extrapolation method
A new technique for extracting the red edge position from hyperspectral data: The linear extrapolation method
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DOI：
10.1016/j.rse.2005.12.011
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发表时间：
2006-03-30
影响因子：
13.5
通讯作者：
Skidmore, AK
中科院分区：
文献类型：
--
作者：
Cho, MA;Skidmore, AK
在光谱反射特征的红边区域（680 ~ 780 nm），拐点的位置被称为红边位置（REP），它受生物化学和生物物理参数的影响，并被用作估计叶片叶绿素或氮含量的手段。本文报道了一种从高光谱数据中提取REP的新技术，该技术旨在缓解由于导数光谱上存在双峰特征而导致的REP与氮含量之间关系的不连续。它是基于一阶导数反射光谱的远红光（680至700 nm）和近红外（725至760 nm）两侧直线的线性外推。然后用两条线交点处的波长值来定义REP。输出为REP方程，REP=-(c(1)-c(2))/(m(1) - m(2))，其中c(1)和c(2), m(1)和m(2)分别表示远红线和近红线的截距和斜率。通过对黑麦冠层、玉米叶片和草/草本混合叶片的光谱数据进行分析，发现679.65和694.30 nm远红波段与732.46和760.41 nm近红外波段、723.64和760.41 mn的组合是计算氮敏感rep的最佳组合。采用线性外推法提取的REPs在宽、窄带宽光谱下均与叶片氮浓度高度相关，与传统的线性插值、多项式和倒高斯拟合方法的结果相当。此外，新方法与线性插值法一样简单，但在不同发育阶段的玉米叶片和低氮浓度的草/草混合叶片上的效果优于线性插值法。(c) 2006爱思唯尔公司版权所有。
The position of the inflexion point in the red edge region (680 to 780 nm) of the spectral reflectance signature, termed the red edge position (REP), is affected by biochemical and biophysical parameters and has been used as a means to estimate foliar chlorophyll or nitrogen content. In this paper, we report on a new technique for extracting the REP from hyperspectral data that aims to mitigate the discontinuity in the relationship between the REP and the nitrogen content caused by the existence of a double-peak feature on the derivative spectrum. It is based on a linear extrapolation of straight lines on the far-red (680 to 700 nm) and NIR (725 to 760 nm) flanks of the first derivative reflectance spectrum. The REP is then defined by the wavelength value at the intersection of the two lines. The output is a REP equation, REP=-(c(1)-c(2))/(m(1) - m(2)), where c(1) and c(2), and m(1) and m(2) represent the intercepts and slopes of the far-red and NIR lines, respectively. Far-red wavebands at 679.65 and 694.30 nm in combination with NIR wavebands at 732.46 and 760.41 nm or at 723.64 and 760.41 mn were identified as the optimal combinations for calculating nitrogen-sensitive REPs for three spectral data sets (rye canopy, and maize leaf and mixed grass/herb leaf stack spectra). REPs extracted using this new technique (linear extrapolation method) showed high correlations with a wide range of foliar nitrogen concentrations for both narrow and wider bandwidth spectra, being comparable with results obtained using the traditional linear interpolation, polynomial and inverted Gaussian fitting techniques. In addition, the new technique is simple as is the case with the linear interpolation method, but performed better than the latter method in the case of maize leaves at different developmental stages and mixed grass/herb leaves with a low nitrogen concentration. (c) 2006 Elsevier Inc. All rights reserved.