NDVI
Definition
Normalised Difference Vegetation Index. Computed as (NIR-Red)/(NIR+Red) from multispectral imagery. Values near 1 indicate dense healthy vegetation; values near 0 indicate bare soil; negative values indicate water or snow. Anomalously low or high values over a suspected burial can flag disturbance or nutrient enrichment.
- Formula
- (NIR - Red) / (NIR + Red)
- Healthy vegetation
- Values near 1
- Bare soil
- Values near 0
Common questions
What does NDVI actually measure?+
NDVI measures vegetation health by comparing how much near-infrared and red light a surface reflects. It's calculated as (NIR-Red)/(NIR+Red) from satellite or aerial images. A value close to 1 means healthy dense vegetation, close to 0 means bare soil, and negative values indicate water or snow.
How can NDVI help find a burial site?+
When soil is disturbed (like at a grave), vegetation grows differently or the soil composition changes. These disturbances show up as NDVI anomalies. Forensic teams use satellite or drone imagery to spot these localised patches of unusual vegetation health or decomposition products that flag a suspected burial.
What imagery is needed to calculate NDVI?+
You need multispectral imagery that captures both near-infrared and red wavelengths. Satellite systems, aerial sensors, and some drones collect this data. The two bands are then combined mathematically to produce the NDVI value for each pixel.
Related terms
- Crop mark
- A differential growth or colour pattern in surface vegetation caused by a sub-surface soil change, including disturbance from digging, which alters moisture...
- Ground sampling distance (GSD)
- The dimension on the ground represented by one pixel in an image. A 10 m GSD means each pixel covers a 10...
- Multi-temporal analysis
- Comparison of imagery acquired at different dates to detect change. A soil disturbance present in a 2009 image but absent in 2005...
- NDWI
- Normalised Difference Water Index. Computed from green and near-infrared or shortwave-infrared bands. Sensitive to water content in vegetation canopy and surface soil....
- Orthomosaic
- A geometrically corrected image assembled from many overlapping photographs, with a consistent scale across its extent. UAV-derived orthomosaics can be georeferenced to...
- SfM (Structure from Motion)
- A photogrammetric method that builds a 3D point cloud and orthomosaic from overlapping images by computing camera positions and feature matches. Standard...
- Synthetic Aperture Radar (SAR)
- An active microwave sensor that generates its own energy pulse and measures the return from the surface. Cloud-penetrating and day/night capable. Backscatter...
- Temporal change detection
- The comparison of multi-date images of the same area to identify pixels or features that have changed between acquisition dates. A disturbed...
- Thermal infrared (TIR)
- Sensor bands measuring emitted heat radiation (approximately 8-14 micrometres). Decomposing organic matter generates heat; soil with high moisture retains heat longer than...
- UNOSAT
- The UNODC Satellite Centre, a UN programme that provides satellite-derived analysis in support of humanitarian and legal investigations, including imagery used for...
Explained in these topics
- Aerial and Satellite Remote SensingNormalised Difference Vegetation Index: a ratio of near-infrared to red reflectance that quantifies vegetation health. Disturbed soil or decomposition products...
- Remote Sensing: Satellite, Aerial, and UAV ApplicationsNormalised Difference Vegetation Index. Computed as (NIR-Red)/(NIR+Red) from multispectral imagery. Values near 1 indicate dense healthy vegetation; values nea...