Which type of image may require georeferencing if it lacks spatial reference?

Raster scans of physical maps may require georeferencing if they lack spatial reference because these scans are direct digital reproductions of physical maps. Unlike satellite imagery or aerial photography, which are sourced from georeferenced data and typically contain inherent spatial information tied to GPS coordinates, raster scans may not automatically include any geographic context. When a physical map is scanned, it becomes a raster image that does not have a projection or coordinate system assigned, meaning that it represents visual information without defining its location in space.

To utilize such a raster scan effectively in a GIS environment, it is essential to apply georeferencing. This process involves identifying control points that can be located on the scanned image and correspond to real-world coordinates, allowing users to assign spatial references to the raster scan. Without georeferencing, the raster scans would remain isolated data lacking spatial correlation with other map layers or datasets.