asvi

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Description

Generates an Atmospheric and Soil Vegetation Index map

Arguments and Return Values

Arguments: 1- or 2-dimensional greyscale images representing near-infrared, red, and blue spectral bands (all three are required)

Return Value: A float greyscale image

Usage

Syntax: asvi(nir, red, blue)

This function is part of the larger class of vegetation-index methods used in satellite image-processing. See ndi or this discussion of related functions for more detailed information.

ASVI is of the subtype which will return both positive and negative values. Positive values generally indicate the presence of vegetation (with greater values indicating healthier vegetation). Negative values generally indicate a lack of vegetation (water, rock, soil, etc.).

The formula used is:

ASVI = NIR + 0.5 - (0.5 * (Sqrt(((2 * NIR + 1)^2) - 8 * (NIR - (2 * Red) + Blue)))

This formula was obtained from "Above-Ground Biomass Estimation of Successional and Mature Forests Using TM Images in the Amazon Basin" (Dengsheng Lu, Paul Mausel, Eduardo Brondizio, and Emilio Moran, 2002).

Examples

dv> nir
2000x1000x1 array of float, bsq format [8,000,000 bytes]

dv> r
2000x1000x1 array of float, bsq format [8,000,000 bytes]

dv> b
2000x1000x1 array of float, bsq format [8,000,000 bytes]

dv> result = asvi(nir, r, b)
Generating an Atmospheric and Soil Vegetation Index image.
2000x1000x1 array of float, bsq format [8,000,000 bytes]

dv> max(result)
1.101486206

dv> min(result)
-0.3954681158

Images

Full set of LandSat 7 imagery:

NYC-Band Comparison.PNG

Output of asvi():

Vegetation Index-NYC-ASVI.PNG

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Recent Library Changes

Created On: 07-16-2012
Modified On: 05-02-2013

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