Software documentation Open Access

Algorithm theoretical basis documentation for an operational snow cover product from Sentinel-2 and Landsat-8 data (Let-it-snow)

Gascoin Simon; Grizonnet Manuel; Klempka Tristan; Salgues Germain

This document describes the algorithm of the Let-it-snow (LIS) processing chain to generate the snow cover extent product for the Theia land data center. The algorithm takes as input a Sentinel-2 or Landsat-8 image of surface reflectance corrected from atmospheric and slope effects, the associated cloud mask (level 2A product provided by Theia) and a digital elevation model. The output is a single band raster at the same resolution of the input image giving the snow presence or absence and a cloud mask. The output cloud mask is different from the input cloud mask because some pixels can be reclassified as snow or no-snow by the algorithm.

The snow detection algorithm works in two passes: first the most evident snow cover is detected using a set of conservative thresholds, then these snow pixels are used to determine the lowest elevation of the snow cover. A second pass is performed for the pixels above this elevation with a new set of less conservative thresholds.

The processing chain also generates a vectorized version of the snow mask after pass 1 and 2 and a color composite that is overlaid by these polygons. These secondary products are intended for expert validation purpose.

Files (15.2 MB)
Name Size
15.2 MB Download
All versions This version
Views 569569
Downloads 579579
Data volume 8.8 GB8.8 GB
Unique views 526526
Unique downloads 502502


Cite as