Vegetation Change in China

Perpendicular Vegetation Index (PVI)

This VI allows for soil lines of different slope, but it is highly sensitive to atmospheric variation:

PVI = sin(a)NIR-cos(a)red; where a = the angle between the soil line and the NIR(Richardson and Wiegand, 1977).

 

Weighted Difference Vegetation Index (WDVI)

A parsimonious use of the concept from PVI with similar sensitivities,

WDVI = NIR - g * red; where g is the soil line slope (Clevers, 1988).

 

Percentage Vegetation Index (PVI)

Crippen (1990) noticed that only the sum of NIR and red was the important use of the red band in NDVI and so merely used IPVI = NIR/(NIR+red) which constrains the values from 0 to 1, unlike the range of -1 to 1 for NDVI.