NDVI Range Delta

Land Usev06.00 credits/per_km2

Responsible:Niccolò Calandri

NDVI Range Delta

Overview

The NDVI Range Delta compares the mean vegetation index between two consecutive time periods. The annual NDVI mean represents the average vegetation index value over the period. By computing the difference between the means of two distinct periods, we obtain a measure of how vegetation phenology and dynamics have changed over time.

Formula:

Delta = Mean_NDVI(period 2) - Mean_NDVI(period 1)
Mean_NDVI(period) = mean(NDVI, period)
NDVI = (NIR - RED) / (NIR + RED)

Positive delta: seasonal vegetation variability has increased — potentially indicating partial deforestation (bare soil in winter, regrowth in summer), agricultural changes (shift to more seasonal crops), or vegetation stress reducing winter greenness.
Negative delta: seasonal variability has decreased, suggesting vegetation cover stabilization — possibly associated with reforestation with evergreen species, irrigation maintaining year-round greenness, or urbanization replacing seasonal vegetation with impervious surfaces (consistently low NDVI).
Near-zero delta: vegetation phenology has remained stable between the two periods.

NDVI is the most widely used vegetation index in remote sensing. Changes in seasonal range provide fundamental insights into ecosystem health, ecological restoration effectiveness, and land use change impacts on vegetation dynamics. This indicator is particularly valuable for long-term monitoring of Nature-Based Solutions and ecosystem climate adaptation assessment.

Calculation Methodology

Data acquisition: Sentinel-2 images are collected for both reference periods, applying cloud (SCL band) and shadow masks.
NDVI calculation: NDVI is computed for each image using NIR (B8, 10m) and RED (B4, 10m) bands, resampled to 15m.
Compositing: temporal composites (median or maximum) are generated to reduce noise and cloud-related gaps.
Mean calculation for period 1: mean NDVI is computed pixel-wise across all valid scenes of the first period.
Mean calculation for period 2: the same mean calculation is repeated for the second period.
Delta calculation: pixel-wise subtraction: Delta = Mean(period 2) - Mean(period 1).
Validation: pixels lacking valid data in either period are masked as NoData.

Data Sources

Source Code	Name	Provider	Resolution	Availability
WRD_S2XXX_99	Sentinel-2 MSI L2A	ESA/Copernicus	15m (10m native NIR/RED)	From 2015

Technical Notes

The effective 15m resolution is obtained by resampling Sentinel-2 10m bands (B4, B8).
Comparison requires valid data in both periods. Regions with frequent cloud cover may have significant gaps.
Changes in agricultural practices (crop rotation, new crops) may generate significant deltas unrelated to environmental degradation.

References

Rouse, J.W., et al. (1974). "Monitoring vegetation systems in the Great Plains with ERTS." Proceedings of the Third ERTS Symposium, NASA SP-351, 309-317.
Tucker, C.J. (1979). "Red and photographic infrared linear combinations for monitoring vegetation." Remote Sensing of Environment, 8(2), 127-150.

Data Sources & References

Sources

WRD_S2XXX_99

Methodology

Il delta del range dell'NDVI viene calcolato confrontando i range annuali dell'indice di vegetazione tra due periodi consecutivi. Per ciascun periodo si calcola la media dell'NDVI. Il delta è ottenuto tramite sottrazione pixel per pixel: Delta = Media(periodo 2) - Media(periodo 1). I dati provengono da Sentinel-2 (bande NIR B8 e RED B4) con risoluzione 15m.