Published on 12 November 2025

swissEO NDVIdiff

The difference in the “Normalized Difference Vegetation Index” (NDVI) shows the annual change in forest areas, derived from satellite data.

NDVI differences provide insights into yearly changes in forests, as NDVI approximates the chlorophyll content (the “greenness”) of vegetation. Chlorophyll absorbs red light, since this wavelength is used for photosynthesis. The healthier—and usually greener—the plant, the higher its chlorophyll content and the greater its absorption of red light. In addition, healthy plants reflect a larger portion of near-infrared light than stressed or diseased plants. Therefore, the NDVI can be calculated from the ratio of red and near-infrared light components, with higher NDVI values indicating healthier vegetation.

For practical use, NDVI values from two consecutive years are compared. The NDVI values from the previous year’s period are subtracted from those of the current period to obtain a measure of annual change. The greater the difference, the more extreme the change between years.
Positive differences indicate early leaf development, general tree growth, or recovery after a stressful year. Negative differences result from early leaf discoloration, windthrow, forest fires, disease or insect infestations, or other natural (e.g., drought stress) or human-made phenomena (such as forest management measures like logging or land-use changes).
Interpreting NDVI changes therefore requires knowledge of local events and the conditions of the previous year.

Data representation and availability

The current dataset can be viewed in the BGDI map viewer via: https://map.geo.admin.ch/?layers=ch.swisstopo.swisseo_ndvi_diff_v100 . In the BGDI WMS the dataset can be displayed by using the layer «ch.swisstopo.swisseo_ndvi_diff_v100» .

To display older datasets in the BGDI map viewer, URL parameterization is required. Replace <id> in the following link with the end date of data acquisition in the format yyyy-mm-ddT235959 (example: 2023-09-30T235959):

https://map.geo.admin.ch/index.html?layers=WMS||ndvi_diff_v100_<id>||https://wms.geo.admin.ch/?item=<id>||ch.swisstopo.swisseo_ndvi_diff_v100||1.3.0

Example for the dataset of August/September 2023:

https://map.geo.admin.ch/index.html?layers=WMS||ndvi_diff_v100_2023-09-30T235959||https://wms.geo.admin.ch/?item=2023-09-30T235959||ch.swisstopo.swisseo_ndvi_diff_v100||1.3.0

Further information

• Technical details

  • Coordinate system: CH1903+ LV95 (EPSG:2056)
  • Resolution: 10 m
  • Temporal resolution: Monthly in summer (June/July, July/August, August/September)
  • Data format: Cloud Optimized GeoTIFF (COG)
  • Interfaces: STAC, WMS
  • Source code used for production: https://github.com/swisstopo/topo-satromo/

• Produktinhalte

  The swissEO NDVIdiff product contains seven elements, all available for direct download:*

  • FOREST-10M: This grid contains NDVI differences masked for forest areas in Switzerland. Resolution: 10 m. (Preview, sample data)
  • PIXELCOUNT-10M: This raster contains two bands (period under review and previous year's period), each quantifying the number of data sets used to calculate the NDVI for each pixel. Resolution: 10 m. (sample data)
  • FOREST-WARNREGIONS-CSV: CSV file with the average NDVI difference and the percentage availability of valid values across forest areas per warning region. (Sample data)
  • FOREST-WARNREGIONS-CSV: CSV file with the average NDVI difference and the percentage availability of valid values across forest areas per warning region. (Sample data)
  • FOREST-WARNREGIONS-GEOJSON: GeoJSON file with the average NDVI difference and the percentage availability of valid values across forest areas per warning region. The coordinates of the warning regions and their bounding boxes are also included. (Sample data)
  • FOREST-WARNREGIONS-PARQUET: Parquet file with the average NDVI difference and the percentage availability of valid values across forest areas per warning region. The coordinates of the warning regions and their bounding boxes are also included. (Sample data)
  • METADATA: JSON file with all necessary information for each element of the product. (Sample data)
  • THUMBNAIL: A reduced JPEG image of the NDVI difference for faster previewing. (Preview)

  *All sample data and previews refer to the latest product update.

• Detailed product information

  The swissEO NDVIz product is based on remote sensing data from polar-orbiting satellites. The optical data (Sentinel-2), processed in the "swissEO S2-SR" product, have a spatial resolution of 10 m and cover the entire area of Switzerland approximately every five days since spring 2017.
  The swissEO S2-SR product uses provided masks (cloud and terrain shadow) to exclude all clouds and cloud shadows. Pixels with illumination angles above 65° are identified and masked as potentially problematic, since their reflection values cannot be reliably interpreted due to extreme oblique lighting.

  From the swissEO S2-SR product, NDVI is calculated as the ratio of near-infrared to red light (Tucker, 1979): (Tucker, 1979):

  NDVI = (NIR - Red) / (NIR + Red)

  To assess NDVI change, the difference between two time periods is calculated. For two consecutive years, the median NDVI for each 10 m pixel is computed over a two-month window (e.g., June–July):

  NDVIdiff = NDVI_{recent period} - NDVI_{previous year's period}
  

  Because NDVIdiff was developed for forest areas, appropriate masking is applied. Based on category 6 (forests) of the Swiss Habitat Map, "swissEO NDVIz" includes only those 10 m pixels that are fully forest-covered. For the Principality of Liechtenstein, the corresponding category from the CLC+Backbone dataset was used.

  This dataset was developed in collaboration with the Bern University of Applied Sciences BFH-HAFL and the Federal Office for the Environment (FOEN) for waldmonitoring.ch.
  The vegetation data are based on optical satellite imagery from the European Space Agency (ESA – Sentinel-2), processed in the swissEO S2-SR product.

• Additional content information

  • swissEO NVDIz - Additional content info

    PDF401.52 kB30 October 2025

Access to raw data

The data can be accessed via the STAC Collection «ch.swisstopo.swisseo_vhi_v100» in the STAC interface of BGDI:

• Browser and download interface: swissEO NDVIdiff: NDVI change (admin.ch)
• Download API documentation: REST Interface: Spatial Temporal Asset Catalog API (admin.ch)
• Google Earth Engine: NDVI difference Image Collection [projects/satromo-prod/assets/col/NDVIdiff_SWISS]
• Accessing STAC via Python - Introduction (Jupyter Notebook)
• Image processing using Python with STAC (Jupyter Notebook)
• Streaming swissEO products in QGIS

Terms of use

swissEO may be used, distributed and made accessible. Furthermore,it may be enriched and processed and also used commercially. A reference to the source is mandatory. In the case of digital or analogue representations and publications, as well as in the case of dissemination, the following source references must be attached in any case:

© swisstopo, Contains modified Copernicus Sentinel data [Year]

Further information on the terms of use can be found on the terms of use webpage.