BSI
Bare Soil Index. A spectral index designed to identify and map bare soil areas by combining blue, red, near-infrared, and shortwave infrared bands. Useful for erosion monitoring, land degradation assessment, and agricultural management.
Overview
The Bare Soil Index (BSI) identifies exposed soil surfaces using four spectral bands: blue, red, NIR, and SWIR. It distinguishes bare ground from vegetation and water for erosion monitoring, land degradation assessment, and agricultural fallow detection.
How It Works
BSI = ((SWIR + Red) − (NIR + Blue)) / ((SWIR + Red) + (NIR + Blue)). On Sentinel-2: ((B11 + B4) − (B8 + B2)) / ((B11 + B4) + (B8 + B2)). Exposed soil produces high values because it reflects strongly in SWIR and Red. Vegetation produces low or negative values.
Key Facts
- Uses four spectral bands: Blue, Red, NIR, and SWIR.
- Often combined with NDVI for thorough land cover analysis.
- Multiple BSI formulations exist — specify which formula when reporting results.
- Sentinel-2 bands: B2, B4, B8, and B11.
Applications
Erosion Monitoring
Mapping areas of exposed soil vulnerable to wind and water erosion.
Land Degradation Assessment
Tracking loss of vegetation cover in dryland ecosystems.
Agricultural Fallow Detection
Identifying unplanted fields between growing seasons.
Limitations & Considerations
Can confuse built-up surfaces with bare soil. Dark organic soils produce weaker signals. Wet soils have depressed SWIR reflectance. Threshold values require regional calibration.
History & Background
The four-band BSI formula gained adoption through land cover classification workflows with Landsat and Sentinel-2 data. A Modified BSI was later developed for tropical agricultural regions.
Related Terms
Analyze BSI data with LYRASENSE
Use our agentic notebook environment to work with satellite data and compute indices like BSI — no setup required.