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REMOTE SENSING INDICES



Remote sensing indices are band ratios designed to highlight specific surface features (vegetation, soil, water, urban areas, snow, burned areas, etc.) using the spectral reflectance properties of the Earth's surface.
They improve classification accuracy and environmental monitoring.

1. Vegetation Indices

NDVI – Normalized Difference Vegetation Index

Formula: (NIR – RED) / (NIR + RED)
Concept: Vegetation reflects strongly in NIR and absorbs in RED due to chlorophyll.
Measures: Vegetation greenness & health
Uses: Agriculture, drought monitoring, biomass estimation

EVI – Enhanced Vegetation Index

Formula: G × (NIR – RED) / (NIR + C1×RED – C2×BLUE + L)
Concept: Corrects for soil and atmospheric noise.
Measures: Vegetation vigor in dense canopies
Uses: Tropical rainforest mapping, high biomass regions

GNDVI – Green Normalized Difference Vegetation Index

Formula: (NIR – GREEN) / (NIR + GREEN)
Concept: Uses Green instead of Red
Measures: Photosynthetic activity & early plant stress
Uses: Precision agriculture, crop nitrogen assessment

SAVI – Soil Adjusted Vegetation Index

Formula: (NIR – RED) / (NIR + RED + L) × (1 + L)
Concept: Reduces soil brightness effect
Measures: Vegetation greenness in soil-exposed areas
Use: Semi-arid & sparse vegetation regions

DVI – Difference Vegetation Index

Formula: NIR – RED
Concept: Simple difference of reflectance
Measures: Vegetation amount
Use: Biomass estimation, quick vegetation change detection

NDRE – Normalized Difference Red Edge Index

Formula: (NIR – Red Edge) / (NIR + Red Edge)
Concept: Uses red-edge band sensitive to chlorophyll concentration
Use: Crop stress detection, nitrogen mapping

TVI – Transformed Vegetation Index

Formula: 0.5 × [1 + (NIR – RED)/(NIR + RED)]
Concept: Reduces saturation in dense vegetation
Use: Forest canopy monitoring

RVI – Ratio Vegetation Index

Formula: NIR / RED
Concept: Simple ratio
Use: Vegetation vigor detection in early remote sensing studies

CVI – Chlorophyll Vegetation Index

Formula: (NIR / GREEN) – 1
Concept: Estimates chlorophyll density
Use: Crop growth monitoring

VHI – Vegetation Health Index

Formula: VHI = a × NDVI + b × TCI (Temp Condition Index)
Concept: Combines vegetation + temperature
Use: Drought disaster monitoring

2. Water Indices

NDWI – Normalized Difference Water Index (McFeeters)

Formula: (GREEN – RED) / (GREEN + RED)
Concept: Water reflects more in Green than Red
Use: Water body extraction

MNDWI – Modified NDWI

Formula: (GREEN – SWIR) / (GREEN + SWIR)
Concept: Replaces RED with SWIR → SWIR strongly absorbs water
Use:

  • Urban water mapping

  • Flood detection

  • Wetland monitoring

DPSI – Difference Pond Snow Index (non-standard but used in snow/water mapping)

Formula: (NIR – BLUE)/(NIR + BLUE)
Use: Snow/ice and water differentiation

3. Snow / Ice Indices

NDSI – Normalized Difference Snow Index

Formula: (GREEN – SWIR) / (GREEN + SWIR)
Concept:

  • Snow = high reflectance in Green

  • Snow = strong absorption in SWIR
    Use: Snow area monitoring & glacier mapping

4. Soil Indices

NDSI (Soil Index Variant)

Formula: (NIR – SWIR)/(NIR + SWIR)
Measures: Soil moisture & soil brightness
Use: Soil property analysis

BSI – Bare Soil Index

Formula: (SWIR + RED) – (NIR + BLUE) / (SWIR + RED) + (NIR + BLUE)
Concept: Distinguishes bare soil from vegetation or water
Use:

  • Land degradation

  • Construction site detection

  • Soil exposure mapping

5. Urban Indices

NDBI – Normalized Difference Built-up Index

Formula: (SWIR – NIR) / (SWIR + NIR)
Concept: Built-up areas have higher SWIR reflectance than NIR
Use: Urban mapping & monitoring

UI – Urban Index

Formula: (SWIR – NIR) / (SWIR + NIR)
Concept: Similar to NDBI
Use: Urban impervious surface detection

Built-up Area Index (Variant)

Formula: (RED – SWIR)/(RED + SWIR)
Use: Urban development measurement

6. Burn & Fire Indices

NBR – Normalized Burn Ratio

Formula: (NIR – SWIR) / (NIR + SWIR)
Concept:

  • Healthy vegetation = high NIR, low SWIR

  • Burned areas = low NIR, high SWIR
    Uses:

  • Forest fire severity

  • Post-fire assessment

  • Burn scar mapping

7. Atmospheric Correction & General Indices

VARI – Visible Atmospherically Resistant Index

Formula: (GREEN – RED)/(GREEN + RED – BLUE)
Concept: Minimizes atmospheric influence in visible imagery
Uses:

  • Vegetation mapping in haze

  • UAV / drone imagery analysis

ARVI – Atmospherically Resistant Vegetation Index

Formula: NIR – (2×RED – BLUE) / NIR + (2×RED – BLUE)
Concept: Corrects atmospheric scattering using Blue band
Use: Vegetation mapping in polluted / hazy regions


IndexPrimary Application
NDVI, GNDVI, SAVI, EVIVegetation health
NDREChlorophyll stress
NDWI, MNDWIWater detection
NDSISnow/Ice mapping
NDBI, UIUrban built-up detection
BSIBare soil identification
NBRBurned area detection
VARI, ARVIAtmospheric resistance
CVIChlorophyll estimation
VHIDrought & vegetation stress
DPSIIce/snow discrimination
RVI, TVI, DVIGeneral vegetation indices


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