‹ volver al glosario de SIG

EVI2 (2-band Enhanced Vegetation Index)

Definition

The 2-band Enhanced Vegetation Index (EVI2) is a modified version of the original Enhanced Vegetation Index (EVI) that does not require the blue reflectance band. It was developed to maintain the advantages of EVI—such as reduced saturation and decreased soil and atmospheric influences—while being compatible with sensors that lack a blue band, such as many historical and current satellite systems (e.g., AVHRR).

Application

EVI2 is particularly valuable for constructing long-term, consistent global vegetation time series by bridging data from sensors with different band configurations. It is used in climate change studies to analyze decadal trends in vegetation activity, in drought monitoring for its stability under varying atmospheric conditions, and in agricultural monitoring where historical data continuity is essential. Its compatibility with AVHRR data makes it key for extending records back to the 1980s.

FAQ

What is the formula for EVI2 and how does it differ from EVI?

EVI2 is calculated as: EVI2 = 2.5 * (NIR - Red) / (NIR + 2.4 * Red + 1). It is derived from the original EVI formula by eliminating the blue band term and optimizing the coefficients for the red and NIR bands. This simplification allows it to be calculated from sensors without a blue band while aiming to preserve the desirable properties of EVI.

Why was EVI2 created if EVI already exists?

EVI2 was created primarily for backward compatibility and sensor interoperability. Many important long-term data records, especially from the AVHRR sensor, do not have a reliable blue band. EVI2 allows scientists to generate a vegetation index with EVI-like qualities from these datasets, enabling the creation of seamless, multi-decadal vegetation time series by combining data from AVHRR, MODIS, and VIIRS.

Is EVI2 as effective as the original EVI?

Studies show that EVI2 performs very similarly to EVI under most conditions, effectively reducing saturation in high-biomass areas and minimizing soil background noise. Its main compromise is a slightly reduced ability to correct for heavy atmospheric aerosol loads compared to the blue-band-corrected EVI, as it lacks the explicit atmospheric correction term.

When should I choose EVI2 over EVI or NDVI?

Choose EVI2 when:

1) Working with historical sensors like AVHRR that lack a blue band;

2) Creating long-term vegetation records that combine data from multiple sensor generations;

3) A simpler, two-band index with reduced saturation is needed, and precise atmospheric correction for aerosols is less critical. Choose standard EVI when a blue band is available and optimal atmospheric resistance is required.