A raster map is the result of a paper map raster scan.
In a raster scan, an image is cut up into successive samples called pixels, along scan lines. Each scan line is stored as a row of pixel values in an array in a computer system, with coded information about the pixel color. Raster scanning is fast and affordable, and the map display is very accurate when displayed at the scanning scale. However, the use of those data is limited, since they are not structured. On the other hand, this format usually generates heavy files.
More generally, the raster mode is a space modeling computer mode, based on a pixel grid of regular size, with each pixel containing radiometry information.
In general, paper maps, aerial photographs and satellite imagery are displayed with raster data.
The raster mode is opposed to the vector mode.
These routes are often worked out manually, the building process is therefore very slow, and not much optimized : it has to comply with the customers’ constraints (time constraints, access...) and the company’s (working hours, skills, overtime...)