Glossary
NDVI (Normalized Difference Vegetation Index)
A multispectral index (NIR − Red) / (NIR + Red) that ranges from -1 to 1 and quantifies how vigorous a canopy is — used in drone crop monitoring to spot stress before it is visible to the eye.
Definition
NDVI is calculated from two bands captured by a multispectral camera: near-infrared (NIR) and red. Healthy vegetation reflects strongly in NIR and absorbs red light for photosynthesis, so the index is high (typically 0.6–0.9) over a vigorous canopy. Stressed plants reflect less NIR and more red, dropping the index toward 0.2–0.4. Bare ground and water fall near zero or negative.
In an Alberta Context
A drone-mounted multispectral camera flown at boot or early flowering can map an NDVI raster of an entire Alberta quarter in 15–30 minutes. Variations within the field reveal nutrient deficiencies, disease patches, herbicide misses, and frost lines two to three weeks before they would be picked up from the cab. NDVI rasters from successive flights also form the basis for variable-rate fungicide or fertilizer prescription maps.
Why It Matters
NDVI lets an operator find and address yield-limiting problems while they are still treatable in-season, rather than diagnosing them at harvest. It is also a standard input for AFSC insurance disputes, frost / hail damage assessments, and the kind of comparative case-study evidence growers expect before adopting a new practice or product.