Zonal Filtering
Definition
Zonal filtering applies filters within the confines of polygons, preserving feature edges when smoothing or enhancing raster data. Instead of a global kernel, the operation respects boundaries, preventing spillover across zones that would mix contexts.
Application
Used in environmental indicators by administrative unit, noise modeling per parcel, or cleaning classification noise within managed fields without affecting neighbors.
FAQ
What benefits does zonal filtering provide over global smoothing?
It prevents edge bleeding that corrupts statistics in adjacent zones and maintains interpretability tied to jurisdictional areas.
How do kernel size and shape influence results?
Larger kernels smooth more but risk overfitting within small zones; anisotropic kernels can align with known gradients.
What pitfalls occur with tiny or irregular zones?
Insufficient samples lead to artifacts; consider merging or using model-based smoothing with partial pooling.
How should performance be managed at scale?
Tile processing and parallelization, with careful handling of zone boundaries and halo regions for correct results.
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