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ARVI (Atmospherically Resistant Vegetation Index)

Definition

The Atmospherically Resistant Vegetation Index (ARVI) is an enhanced vegetation index designed to minimize atmospheric effects, particularly from aerosol scattering, by using the blue band to correct the red band before calculating the index. It builds upon the NDVI formula but incorporates an atmospheric correction term, making it more robust in hazy, smoky, or polluted conditions.

Application

ARVI is particularly valuable in regions with frequent haze, aerosol pollution, or biomass burning smoke, where standard NDVI becomes unreliable. It is used for accurate vegetation monitoring in urban areas, industrial regions, post-fire landscapes, and in long-term global change studies where atmospheric clarity varies over time.

FAQ

What is the formula for ARVI and how does it work?

ARVI is calculated as: ARVI = (NIR - RB) / (NIR + RB), where RB = Red - γ * (Blue - Red). The γ parameter (usually 1.0) determines the strength of atmospheric correction. This formulation uses the difference between blue and red reflectance to estimate and remove atmospheric scattering effects from the red band.

How does ARVI improve upon NDVI in atmospheric conditions?

ARVI improves upon NDVI by explicitly accounting for Rayleigh and aerosol scattering through the blue-band correction. While NDVI assumes minimal atmospheric influence, ARVI recognizes that scattering affects shorter wavelengths (blue) more than longer ones (red), and uses this relationship to derive a corrected red reflectance, resulting in a more stable vegetation signal.

When should I choose ARVI over other vegetation indices?

Choose ARVI when:

1) Working in atmospherically unstable environments (urban haze, dust, smoke);

2) Comparing vegetation across different dates with varying atmospheric conditions;

3) Using sensors with reliable blue bands (e.g., MODIS, Sentinel-2, Landsat 8/9);

4) Maximum resistance to aerosol effects is needed without moving to more complex radiative transfer models.

What are the limitations of ARVI?

Limitations include:

1) Requires a blue band, excluding some historical sensors;

2) Assumes a specific relationship between atmospheric effects on blue and red bands that may not hold in all conditions (e.g., heavy smoke with large particles);

3) May overcorrect in very clear atmospheric conditions or over dark targets;

4) Slightly more computationally intensive than NDVI and less intuitive to interpret for non-specialists.