# Generated by scripts/sync_indices.py from Awesome Spectral Indices (MIT).
# DO NOT EDIT BY HAND. Edit overlays (_asi_*.yaml, _folia_*.yaml) and re-run.
# Spec: docs/spec/SPECTRAL_INDICES.md
slug: ndrei
name: Normalized Difference Red Edge Index
short_name: NDREI
formula: (N - RE1) / (N + RE1)
bands:
- N
- RE1
domain: vegetation
theme: vegetation
concepts:
- leaf-area-index
rank: 15
display:
  colormap: rdylgn
  range:
  - -0.2
  - 1.0
pedagogy:
  description: 'Normalized Difference Red Edge Index (Gitelson & Merzlyak 1994).

    Replaces NDVI''s red term with Sentinel-2 red-edge band 1 (~705 nm),

    shifting sensitivity from chlorophyll absorption to canopy chlorophyll

    density. Precision-agriculture default on red-edge-equipped sensors.

    '
  use_cases:
  - Within-field nitrogen and chlorophyll status mapping in precision agriculture
  - Late-season crop monitoring where NDVI has long saturated
  - Stress detection at sub-canopy scales (red-edge is more sensitive to chlorophyll than red)
  limitations:
  - Requires a red-edge band — not computable on Landsat, MODIS, or RGB-NIR sensors
  - Saturates later than NDVI but still saturates in extremely dense canopies
  - Often confused with the longer-baseline CIRE — both use NIR + RE1 but with different formulations
  interpretation:
    high: Dense chlorophyll-rich canopy
    mid: Typical green canopy
    low: Sparse / stressed canopy
    negative: Soil, water
  authoritative_sources:
  - label: Gitelson & Merzlyak 1994
    url: https://doi.org/10.1016/1011-1344(93)06963-4
  - label: NV5 ENVI — Narrowband Greenness
    url: https://www.nv5geospatialsoftware.com/docs/NarrowbandGreenness.html
  - label: Index Database · NDREI
    url: https://www.indexdatabase.de/db/i-single.php?id=223
references:
- url: https://doi.org/10.1016/1011-1344(93)06963-4
date_of_addition: '2021-05-13'
contributor: https://github.com/davemlz
platforms:
- Sentinel-2
source:
  authority: awesome-spectral-indices
  commit_sha: 7f28d3fe68af1287f7449faf0685659e73197212
  upstream_id: NDREI
match_tags:
- difference
- edge
- index
- n
- normalized
- re1
- red
- vegetation
status: stable