What are aerial imagery for GIS?

Aerial imagery consists of photographic captures of the Earth's surface from aircraft, drones, or satellites. It provides current or historical views of terrain and is widely used as a background layer in GIS and web maps.

In the Netherlands, aerial and orthophoto imagery is broadly available via PDOK as WMS services. It supports interpretation of topography, land use, and environmental change. Aerial imagery is raster data: each pixel has a color value, not discrete objects with attributes.

Aerial imagery is not the same as orthophotos: raw aerial photos may be distorted by camera angle and terrain. Orthophotos are geometrically corrected and suitable as a map background at scale. For accurate measurement and overlay with BGT/BRT, orthophotos are preferred.