# 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: ndsi
name: Normalized Difference Snow Index
short_name: NDSI
formula: (G - S1) / (G + S1)
bands:
- G
- S1
domain: snow
theme: cryosphere
concepts:
- snow
rank: 7
display:
  colormap: blues
  range:
  - -0.2
  - 1.0
pedagogy:
  description: 'Normalized Difference Snow Index (Hall 1995). Uses the contrast between

    visible green (high in snow) and shortwave-infrared band 1 (low in

    snow due to ice absorption) to discriminate snow from cloud. The

    basis of the operational MODIS MOD10 snow-cover product.

    '
  use_cases:
  - Daily and seasonal snow-cover area mapping over alpine and polar regions
  - Snowpack phenology and ablation-onset detection
  - Cloud-versus-snow discrimination in optical cloud masks
  limitations:
  - Thin or patchy snow at sub-pixel scales is missed at coarse resolution — use Landsat or Sentinel-2 over MODIS where possible
  - Forest canopy obscures snow underneath — pair with land-cover for forest-area correction
  - Mixed pixels at the snowline are inherently ambiguous; a binary threshold (commonly NDSI > 0.4) hides this uncertainty
  interpretation:
    high: Fresh, clean snow or ice
    mid: Aged or partial snow cover
    low: Snow-free land, soil, vegetation
    negative: Water, dark surfaces
  authoritative_sources:
  - label: Hall, Riggs & Salomonson 1995
    url: https://doi.org/10.1016/0034-4257(95)00137-P
  - label: NV5 ENVI — Snow Indices
    url: https://www.nv5geospatialsoftware.com/docs/AlphabeticalListIndices.html
  - label: Index Database · NDSI
    url: https://www.indexdatabase.de/db/i-single.php?id=376
references:
- url: https://doi.org/10.1109/IGARSS.1994.399618
date_of_addition: '2021-04-07'
contributor: https://github.com/davemlz
platforms:
- Sentinel-2
- Landsat-OLI
- Landsat-TM
- Landsat-ETM+
- MODIS
source:
  authority: awesome-spectral-indices
  commit_sha: 7f28d3fe68af1287f7449faf0685659e73197212
  upstream_id: NDSI
match_tags:
- difference
- g
- index
- normalized
- s1
- snow
status: stable