TechnicalGIS

#Cloud masking

2 posts

Tutorial Python

Sentinel-2 cloud and cloud-shadow masking in Python: SCL vs s2cloudless vs OmniCloudMask

Mask clouds and cloud shadows in Sentinel-2 L2A imagery with Python. Compare the Scene Classification Layer (SCL), s2cloudless, OmniCloudMask and a simple threshold over the Lake District, measure how far they agree, score them against 186 reference points and build a cloud-free median composite.

Intermediate 14 min read

Three panels of the Cairngorms on 25 November 2025: a true-colour Sentinel-2 image with snow on the plateaux and long shadows in the glens; the NDSI, blue over snow and red over forest and bare ground; and a snow map over hillshade, with snow in blue on the high ground around Cairn Gorm, Ben Macdui, Braeriach, Beinn a' Bhuird and Ben Avon, covering 57% of the clear land.

Tutorial Python

Snow cover mapping with NDSI in Python: Sentinel-2 and MODIS over the Cairngorms

Map snow cover in Python with the Normalised Difference Snow Index (NDSI) from Sentinel-2 and the daily MODIS snow product on the Microsoft Planetary Computer: choosing the NDSI threshold, separating snow from cloud, snow-covered area through the winter of 2025–26 in the Cairngorms, and the snowline by elevation and aspect with the Copernicus DEM.

Intermediate 15 min read