A burn index — 23 compatible sensors — Last revised June 1, 2025
VI6T

VI6T Index

VI6T Index - A spectral index for burn applications.

Used in fire & burn mapping.

When to use

  • Post-fire burn perimeter mapping
  • Burn severity classification (low, moderate, high)
  • Vegetation recovery monitoring over years
  • Carbon emission estimation from biomass loss
  • Soil erosion risk assessment in burned watersheds

Limitations

  • Requires both pre-fire and post-fire imagery for accurate severity mapping
  • Vegetation regrowth begins quickly, narrowing the post-fire assessment window
  • Surface moisture from rain after the fire can mask burn signatures
  • Topographic shadows produce false low-severity areas
  • Ground validation needed for fire severity classification accuracy

What the values mean

-1 Unburned / regrowth
-0.1 Low severity
0.1 Moderate-low severity
0.27 Moderate-high severity
0.44 High severity
0.66 Severe (full burn)
Surface typeTypical VI6T
Unburned vegetation< -0.1
Low severity burn-0.1 to 0.1
Moderate burn0.1 to 0.44
High severity, full burn> 0.44

General Formula

N 850

Sensor-Specific Formulas

Most-used sensors — click to show code below

SensorProviderFormulaBand Mapping
BJ3A
21AT(NIR - T/10000.0)/(NIR + T/10000.0)N→NIR
Jilin-1
CG Satellite(NIR - T/10000.0)/(NIR + T/10000.0)N→NIR
Landsat 8/9
USGS/NASA(B5 - T/10000.0)/(B5 + T/10000.0)N→B5
NAIP
USDA(NIR - T/10000.0)/(NIR + T/10000.0)N→NIR
Sentinel-2
ESA(B8 - T/10000.0)/(B8 + T/10000.0)N→B8
WorldView 3
MAXAR(NIR1 - T/10000.0)/(NIR1 + T/10000.0)N→NIR1
WorldView Legion
MAXAR(NIR1 - T/10000.0)/(NIR1 + T/10000.0)N→NIR1

Spectral Band Visualization — BJ3A

Code Examples

Adapted for BJ3A bands —

vi6t_bj3a.py

Frequently Asked Questions

What is the VI6T (VI6T Index) and when should I use it?

VI6T Index - A spectral index for burn applications. Burn severity indices quantify post-fire damage by measuring the spectral changes that occur when vegetation is consumed and the underlying soil and char are exposed. VI6T is particularly suited for burn. The general formula is (N - T/10000.0)/(N + T/10000.0), which requires N spectral bands.

Which satellite sensors can I use to calculate VI6T?

VI6T is supported by 23 satellite sensors in our database, including BJ3A, BJ3N, Dragonette-2/3, Gaofen-1, Gaofen-2 and 18 more. Each sensor uses different band designations — for example, BJ3A uses the formula (NIR - T/10000.0)/(NIR + T/10000.0), while BJ3N uses (NIR - T/10000.0)/(NIR + T/10000.0). Select a sensor above to see its specific band mapping.

What spectral bands does VI6T require and why?

VI6T requires N (850). These wavelength regions target the specific spectral features that this index is designed to measure.

How do I calculate VI6T in Python or R?

Both Python and R code samples are provided above. In Python, use rasterio to load individual band GeoTIFF files and numpy for the arithmetic. In R, the terra package handles raster operations efficiently. The key is to load bands as floating-point arrays to avoid integer division, and to handle division-by-zero cases where the denominator equals zero. For production use, consider applying a valid data mask to exclude no-data pixels before calculation.

VI6T vs other burn indices

IndexNameHow it differs
BAIBurn Area IndexAlternative burn index — different band combination

Related Burn Indices

BAI
Burn Area Index

References

https://doi.org/10.1080/01431160500239008

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