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Crop Agriculture

About NDVI

Related page: 71 VSIs (including NDVI) for broad or narrow band sensors    Why NIR

The Normalized Difference Vegetation Index (NDVI) (Rouse et al., 1973) is one of many vegetation spectral indices - it may or may not be the better option for a particular vegetation application. NDVI takes advantage of the fact that healthier green vegetation has higher near infrared surface reflectance and lower red surface reflectance (has a value between -1.0 and 1.0).

It is calculated as follows: NDVI = (NIR – red) / (NIR + red), where NIR and red are both surface reflectance values.

NDVI has probably been used more that any other index. As a general rule, NDVI senses crop condition well during a certain window early enough in the growing season that the red band has not saturated but late enough that the canopy has closed enough to cover soil enough.

For vegetation assessment purposes, if NIR and red are generally negatively correlating, WE RECOMMEND the Wide Dynamic Range Index, where α = .1 (Gitelson, 2004). For this index, simply multiply NIR surface reflectance by .1 so that it is more equal with red surface reflectance. The index can be written as: ([NIR x .1] - red) / ([NIR x .1] + red).

Wu et al., (2007; pdf) showed that MSAVI is better at detecting leaf area index for corn and potatoes than NDVI and other indices. MSAVI emphasises the NIR band than NDVI does.

 

Reference

Gitelson, A.A. 2004. Wide dynamic range vegetation index for remote quantification of biophysical characteristics of vegetation. Journal of Plant Physiology 161; pp. 165–173.

Rouse, J.W., R.H. Haas, J.A. Schell, and D.W. Deering. 1973. Monitoring vegetation systems in the Great Plains with ERTS. Third ERTS Symposium, NASA SP-351 I: 309-317.

Wu, J., Wang, D, and M.E. Bauer. 2007. Assessing broadband vegetation indices and QuickBird data in estimating leaf area index of corn and potato canopies. Field Crops Research 102 (2007) 33–42.