Which overlay is best for representing spatially continuous phenomena like pollution gradients?

• A. Raster Overlay
• B. Vector Overlay
• C. Point Overlay
• D. Attribute Overlay

Answer: (A)

Representing a spatially continuous phenomenon like a pollution gradient is most naturally done with a raster overlay because space is treated as a continuous field, and each cell in a raster holds a value that represents the level of pollution at that location. This grid of values creates a continuous surface, so gradual changes from low to high concentrations appear as smooth gradients across neighboring cells. Vector overlays, by contrast, are built from discrete features with defined boundaries, which is ideal for boundaries and networks but not for depicting a smooth field. Point overlays only mark individual locations, not the surrounding gradient, and attribute overlays add data to features without showing spatial variation across the landscape. So, for a gradient that changes gradually across space, a raster representation provides the most intuitive and effective visualization.