# 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: sipi
name: Structure Insensitive Pigment Index
short_name: SIPI
formula: (N - A) / (N - R)
bands:
- N
- A
- R
domain: vegetation
theme: vegetation
concepts: []
rank: 25
display:
  colormap: rdylgn
  range:
  - 0.0
  - 2.0
pedagogy:
  description: 'Structure Insensitive Pigment Index (Penuelas 1995). Uses NIR, blue

    (~445 nm) and red bands to estimate the bulk carotenoid-to-chlorophyll

    ratio while minimising sensitivity to canopy structure. A leading

    indicator of plant stress.

    '
  use_cases:
  - Pre-visual stress detection — the carotenoid/chlorophyll ratio shifts before LAI does
  - Disease and senescence onset monitoring in row crops
  - Forest-decline early-warning in conifer monitoring programs
  limitations:
  - The "A" band (coastal aerosol ~445 nm) is unavailable on Landsat 4-7 and MODIS — Sentinel-2 B1 or Landsat 8/9 B1 only
  - Empirical bounds (~0-2) and sensor-specific tuning needed
  - Confounded by stress types that change pigments uniformly rather than the ratio
  interpretation:
    high: Stressed vegetation (high carotenoid relative to chlorophyll)
    mid: Typical canopy
    low: Healthy, chlorophyll-dominant canopy
  authoritative_sources:
  - label: Penuelas 1995
    url: https://eurekamag.com/research/009/395/009395053.php
  - label: NV5 ENVI — Leaf Pigments
    url: https://www.nv5geospatialsoftware.com/docs/LeafPigments.html
  - label: Index Database · SIPI
    url: https://www.indexdatabase.de/db/i-single.php?id=84
references:
- url: https://eurekamag.com/research/009/395/009395053.php
date_of_addition: '2021-09-17'
contributor: https://github.com/davemlz
platforms:
- Sentinel-2
- Landsat-OLI
source:
  authority: awesome-spectral-indices
  commit_sha: 7f28d3fe68af1287f7449faf0685659e73197212
  upstream_id: SIPI
match_tags:
- a
- index
- insensitive
- n
- pigment
- r
- structure
- vegetation
status: stable