Category: Optical and atmosphere
Cloud Shadow
Cloud shadow is the darkening of the surface caused by clouds blocking sunlight, often mistaken for real change.
Also known as: shadow mask, cloud shade
Expanded definition
Cloud shadows reduce measured reflectance because less sunlight reaches the ground. In optical images they can look like burned areas, wet soil, or crop stress if not masked.
Shadow detection is harder than cloud detection because shadows depend on sun angle, cloud height, and terrain. Shadows can also blend into natural dark features such as water bodies or conifer forests.
If your workflow uses thresholds or anomaly detection, cloud shadows are a major source of false positives. Using shadow-aware masks and temporal consistency checks reduces those errors.
Related terms
Cloud Mask
A cloud mask labels pixels likely affected by clouds so they can be excluded or handled differently.
Change Detection
Change detection identifies meaningful differences between dates, such as harvest, flooding, deforestation, or construction.
Time Series
A time series is a sequence of observations over time for the same location, used for monitoring and change detection.