GNDVI: Swapping Red for Green to Read Chlorophyll
Chlorophyll absorbs green light less dramatically than red, and that subtlety is the point: GNDVI trades NDVI's red band for green to stay sensitive to canopy chlorophyll and nitrogen well past the point where NDVI has maxed out.
The physical basis
Structurally GNDVI is NDVI with green substituted for red. Green reflectance responds more gradually to rising chlorophyll, so the index keeps climbing at moderate-to-high leaf area where the red band has already saturated. That makes it a better proxy for nitrogen status than raw greenness.
The formula
where NIR is near-infrared reflectance, Green is green reflectance.
Reading the values
Higher = more chlorophyll / nitrogen. More sensitive than NDVI at moderate-to-high leaf area, useful for crop N management.
Which bands to use
| Sentinel-2 | NIR B8 · Green B3 |
| Landsat 8/9 | NIR B5 · Green B3 |
In practice
It is a precision-agriculture favourite for in-season nitrogen management on cereals, and useful for estimating canopy chlorophyll in dense crops where NDVI has gone uninformative.
Where it struggles
At low cover GNDVI is actually weaker than NDVI — green is less distinct from soil than red is — so treat it as a tool for established, leafy canopy, not bare or emerging fields.
Compute GNDVI on your own study area
Skip the code. Draw or upload a boundary and Spatial Research Suite runs GNDVI on live Sentinel-2 or Landsat imagery — with cloud masking, exports and citations built in.
Run this analysis in GISforus →Frequently asked
When is GNDVI better than NDVI?
In dense, established canopy where NDVI has saturated; the green band keeps GNDVI responsive to chlorophyll and nitrogen there.
Is GNDVI good for early-season crops?
Not particularly — at low cover NDVI or SAVI separates vegetation from soil more reliably.