The normalized difference red edge index (NDRE) is a metric that can be used to analyse whether images obtained from multi-spectral image sensors contain healthy vegetation or not. It does this by measuring the amount of chlorophyll in a plant. It is similar to Normalized Difference Vegetation Index (NDVI) but uses the ratio of Near-Infrared and the edge of Red as follows:
NDRE = ( NIR − RE ) ( NIR + RE ) {\displaystyle {\mbox{NDRE}}={\frac {({\mbox{NIR}}-{\mbox{RE}})}{({\mbox{NIR}}+{\mbox{RE}})}}}
The red edge is the part of the spectrum centered around 715 nm. The Index will give a value between -1.0 to +1.0, with a higher value showing a healthy plant environment.
See also Normalized difference water index
References
External links IEE Explore website, Normalized Difference Red-Edge Estimation With Modified DiscoGAN Model, article by Hyeon-Beom Choi, Kwon-Hee Han and Jeongwook Seo (2006) Spectral Reflectance Changes Associated with Autumn Senescence of Aesculus hippocastanum L. and Acer platanoides L. Leaves. Spectral Features and Relation to Chlorophyll Estimation [2] Chlorophyll Absorption Barnes, T.R., Clarke, S.E. Richards et. al. 2000. Coincident Detection of Crop Water Stress, Nitrogen Status and Canopy Density using Ground-Based Multispectral Data. Proceedings of the Fifth International Conference on Precision Agriculture