Satellite Index Calculator
Compute NDVI, NDWI, NDSI, and NBR spectral indices from Sentinel-2 or Landsat 8/9 band GeoTIFFs directly in your browser — with statistics, classification breakdown, and a pseudocolor preview.
Satellite / Sensor
Spectral Index
Band A —
Band B —
Processing raster data…
Computing index pixel by pixel. Large files may take a few seconds.
Computation Error
Classification Breakdown
Pseudocolor Preview
Downsampled preview — actual computation uses full resolution
Computation Reference
How Spectral Index Computation Works
Every spectral index follows the same normalized difference formula: subtract Band B from Band A, then divide by their sum. This produces a value between −1 and +1 for every pixel in the raster. The tool reads your uploaded GeoTIFF files locally — no data is sent to any server — then iterates every pixel pair, computes the index, and maps the result to a pseudocolor preview.
What Is NDVI and How Is It Calculated?
The Normalized Difference Vegetation Index (NDVI) is the most widely used spectral index in remote sensing. It was developed in the 1970s and remains the standard measure for monitoring vegetation health from satellite imagery. NDVI uses the contrast between the Near Infrared (NIR) and Red bands: healthy vegetation absorbs red light strongly for photosynthesis and reflects NIR strongly because of leaf cell structure, producing a high positive NDVI. Bare soil, urban surfaces, and water yield values near zero or negative.
The formula is NDVI = (NIR − Red) / (NIR + Red). Values above 0.6 indicate very dense, healthy canopy such as tropical forest or well-watered cropland. Values between 0.2 and 0.4 represent moderate vegetation like grassland or sparse crops. Values below 0.1 indicate bare soil, rock, sand, or urban areas. Negative values are typical of water bodies, snow, and ice.
For Sentinel-2, upload Band B08 (NIR, 10 m) as Band A and Band B04 (Red, 10 m) as Band B. For Landsat 8 or Landsat 9, upload Band 5 (NIR) as Band A and Band 4 (Red) as Band B. Both bands must be the same spatial resolution — resample to match if needed before uploading.
NDWI, NDSI, and NBR — When to Use Each Index
NDWI — Water Index
Uses Green and NIR bands. Values above 0 indicate open water. Flood mapping, wetland delineation, irrigation monitoring, and dam reservoir tracking are the primary applications. NDWI is complementary to NDVI — water pixels that confuse vegetation maps show up as strong positive NDWI.
NDSI — Snow Index
Uses Green and SWIR bands. Snow reflects strongly in the Green band but absorbs SWIR, while clouds reflect both — NDSI reliably separates snow from cloud. Values above 0.4 indicate snow-covered pixels. Used for glacier monitoring, seasonal snow cover mapping, and avalanche risk assessment.
NBR — Burn Ratio
Uses NIR and SWIR2 bands. Healthy vegetation has high NIR and low SWIR2; burned areas reverse this. The difference between pre-fire and post-fire NBR (dNBR) is the standard metric for fire severity mapping. Used by wildfire managers, insurance analysts, and post-fire rehabilitation planners.
How to Download Sentinel-2 and Landsat Band Files
Sentinel-2 imagery is available free from the Copernicus Data Space Ecosystem (dataspace.copernicus.eu). Search for your area of interest, select a scene with low cloud cover, and download the L2A (surface reflectance) product. Inside the ZIP you will find individual band files named *_B03.tif, *_B04.tif, *_B08.tif, *_B11.tif, and *_B12.tif. B03, B04, and B08 are already at 10 m resolution. B11 and B12 are at 20 m — use QGIS (Raster › Resample) or gdal_translate to upsample them to 10 m before computing NDSI or NBR.
Landsat 8 / Landsat 9 scenes are available from USGS Earth Explorer (earthexplorer.usgs.gov). Download Collection 2 Level-2 Surface Reflectance products. Band files end in _SR_B3.TIF, _SR_B4.TIF, _SR_B5.TIF, _SR_B6.TIF, and _SR_B7.TIF. All Landsat bands at the same scene are already at 30 m resolution, so no resampling is required for index computation.
Spectral Index Band Reference Table
| Index | Satellite | Band A (role) | Band B (role) | Threshold |
|---|---|---|---|---|
| NDVI | Sentinel-2 | B08 — NIR (10 m) | B04 — Red (10 m) | > 0.2 vegetation |
| NDVI | Landsat 8/9 | B5 — NIR (30 m) | B4 — Red (30 m) | > 0.2 vegetation |
| NDWI | Sentinel-2 | B03 — Green (10 m) | B08 — NIR (10 m) | > 0.0 water |
| NDWI | Landsat 8/9 | B3 — Green (30 m) | B5 — NIR (30 m) | > 0.0 water |
| NDSI | Sentinel-2 | B03 — Green (10 m) | B11 — SWIR 1 (20 m) | > 0.4 snow |
| NDSI | Landsat 8/9 | B3 — Green (30 m) | B6 — SWIR 1 (30 m) | > 0.4 snow |
| NBR | Sentinel-2 | B08 — NIR (10 m) | B12 — SWIR 2 (20 m) | < 0.1 burned |
| NBR | Landsat 8/9 | B5 — NIR (30 m) | B7 — SWIR 2 (30 m) | < 0.1 burned |
Frequently Asked Questions
What is a good NDVI value for healthy vegetation?
Why must Band A and Band B have the same dimensions?
What does NDWI above 0 mean in practice?
How is NBR used for wildfire severity mapping?
Can I use this tool with other satellite sensors like MODIS or Landsat 7?
Does my satellite imagery stay private? Is it uploaded to a server?
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