Rasterbasemaps

Raster basemaps are georeferenced raster layers used as the base map in geographic information systems and web mapping applications. They provide background imagery or relief to give geographic context for overlaid vector features or other data.

Raster basemaps are typically composed of uniform grid cells (pixels) arranged in a coordinate reference system and may be stored as formats such as JPEG, PNG, TIFF, or GeoTIFF. For performance in interactive maps, they are often delivered as tiled pyramids using a schema like XYZ tiles or WMTS, allowing rapid rendering at multiple zoom levels.

Common sources include satellite imagery, aerial photography, and derived products such as hillshade or elevation-derived rasters. They can be single-band or multi-band; color composites use three bands. They may be static or updated periodically; dynamic basemaps can be generated on the fly.

In practice, raster basemaps must align with the map's coordinate system and projection. Resampling methods (nearest neighbor, bilinear, bicubic) affect display quality when zooming. CRS consistency and on-the-fly reprojection are important for accurate overlays.

Limitations include large file sizes, storage and bandwidth requirements, and potential licensing restrictions. Raster basemaps are contrasted with vector basemaps, which render geometry and styling in real time and can scale without loss of detail.