Data access

Two Data Levels

Theia Snow product is available with two data levels :

>>> level 2 offers monotemporal data, i.e. from ortho-rectified Sentinel-2 mono-date images, expressed in surface reflectance and accompanied by a cloud mask.

Theia Snow Product
Theia L2-Snow Product detects the presence of snow (in blue) and cloud (in white).

>>> level 3 offers annual syntheses of snow cover duration per pixel between September 1 and August 31

2016-2017 Snow Coverage Synthesis for the Pyrénées (France)
Map of the snow coverage in the Pyrenees during a hydrological year (1 September 2016 to 31 August 2017) produced by synthesis of Theia snow-covered surface products.

Production zone

The product Neige distributed by Theia indicates the presence or absence of snow on land surface every five days in the absence of clouds. It is a 20-m resolution product generated from Sentinel-2 level 2A images produced by Theia and, for this reason, is only available on areas covered by Theia’s production. It is nevertheless possible to request a particular production

Theia Snow Product Production Zone in February 2020.
An interactive map gives more details

A product in constant evolution

The version of the available products will be brought to evolve, in particular to correct the following defects:

  1. Some cold, low elevation, clouds can be wrongly classified as “snow”. These clouds have a spectral signature similar to the one of the snow cover.
  2. Shaded, steep, snow covered slopes can be wrongly classified as “no-snow”, especially in winter when the sun elevation angle is low at the time of the image acquisition. These slopes have a low signal-to-noise ratio and should be considered as no-data.
  3. The product is not reliable in areas of dense forest because the canopy obstructs the surface.

Contact

Simon Gascoin
Cesbio
@S.Gascoin
Contributions

Aurore Dupuis
Cnes
@A.Dupuis

Level

The product is distributed by Theia as a raster file (8 bits GeoTIFF) of 20 m resolution and a vector file (Shapefile polygons)

  1. Raster files are named SENTINEL2A*SNW_R2.tif. Pixels are coded as follows:
    • 0: No-snow
    • 100: Snow
    • 205: Cloud including cloud shadow
    • 254: No data
  2. Vector files are named SENTINEL2A*SNW_R2.{shp,shx,prj,dbf} and coded with the DN field
    • 0: No-snow
    • 100: Snow
    • 205: Cloud including cloud shadow
    • 254: No data

Style files to display the snow product in QGIS (raster and vector) are available.

This video tutorial shows how to download a product from your web browser and display it in QGIS. You can also use this script in python to download the products from your terminal.

Licence

The Sentinel-2 level 2A or 3A data distributed by THEIA are distributed under the ETALAB V2.0 open license, details of which are available here: Français | English.

The processor code and its documentation are available under a free software licence: