This study analyses a Sentinel-2 Level-2A image acquired over Monte Faeta, Tuscany, on 29 April 2026.

The objective is to identify the earliest detectable fire-related signal in the satellite scene using spectral indices.

This analysis does not determine the cause or exact ignition point of the wildfire. It only evaluates spatial patterns of fire-related spectral signals at the time of satellite acquisition.

Data source and processing

  • Satellite: Sentinel-2 L2A (Copernicus Data Space Ecosystem)
  • Sensor: MSI (Multispectral Instrument)
  • Resolution: 10 m (bands resampled where needed)
  • Processing: OpenEO Python workflow
  • Area: 2 km by 2 km region over Monte Faeta

All spectral bands were resampled to a common 10 m grid before index calculation.

All imagery and derived products are based on Copernicus Sentinel-2 data provided by the European Space Agency (ESA) through the Copernicus Data Space Ecosystem. © European Union / ESA, contains modified Copernicus Sentinel data (2026). 1

True colour image

Sentinel-2 true colour composite

Figure 1: True colour composite (B04, B03, B02). 1

The true colour composite shows vegetation, smoke presence, and surface disturbance. Active fire is not clearly visible due to atmospheric effects and band sensitivity.

SWIR response

Sentinel-2 SWIR composite

Figure 2: SWIR composite highlighting thermal disturbance. 1

Shortwave infrared bands (especially B12) are sensitive to high temperature surfaces and burned vegetation.

Elevated SWIR reflectance in the study area indicates fire-related thermal disturbance or recent burning.

Burn detection index

The Normalized Burn Ratio (NBR) is used to detect burned or fire-affected vegetation:

Sentinel-2 NBR severity

Figure 3: Normalized Burn Ratio (NBR). 1

Lower values of NBR indicate burned or heat-affected surfaces.

Earliest detected fire signal

A single pixel shows the strongest and most consistent fire-related spectral response in the scene.

Location: 43.7714°N, 10.4765°E
Spatial resolution: 10 m (Sentinel-2 MSI)

At this location:

  • SWIR reflectance is elevated, consistent with thermal disturbance
  • NBR is strongly negative, consistent with burned vegetation
  • MIRBI is positive, consistent with fire-related surface conditions

These indicators are spatially aligned within the same pixel.

Interpretation

This pixel represents:

The earliest detectable fire-related signal in the Sentinel-2 observation of this area.

This does not indicate the ignition point.

Limitations:

  • Sentinel-2 does not measure temperature directly
  • Each pixel represents a mixed 10 m ground area
  • Fire spread dynamics can shift peak signal location
  • Only a single satellite overpass is available

Conclusion

Within the analysed Sentinel-2 scene:

  • One pixel shows a consistent and strong fire-related spectral signature
  • Multiple independent indices agree on this location
  • This pixel is the highest-confidence fire signal in the dataset

Therefore, it is the earliest detectable fire signal at satellite resolution in this image.

  1. Contains modified Copernicus Sentinel-2 data (2026), processed in a custom workflow. Data sourced from the Copernicus Data Space Ecosystem. © European Union / ESA. ↩ ↩2 ↩3 ↩4