Plants pull a sneaky trick with light: chlorophyll drinks red light for photosynthesis but bounces back invisible near-infrared. NDVI just compares the two bands — the bigger the gap, the healthier the vegetation. Numbers land between −1 (water / shadow) and +1 (lush rainforest). The middle is bare ground.

It’s basically a ‘how green is this place’ score that NASA, USDA, and every satellite ag company uses every day.

🔬 Science / formula

NDVI = (NIR − Red) / (NIR + Red). Range −1 to +1. Rouse et al. (1974).

Well-vegetated: high (0.6–0.8)
Bare rock/sand/snow: ≤ 0.1
Water: negative

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NDVI = Normalized to −1..+1. Unlike SR which has no upper bound, and unlike EVI which adds the Blue band.

veg/ndvi-formula