In scanning, a digital image of the map is produced by moving an electronic detector across the
surface of the map.

There are two types of scanner designs:

Flat-bed scanner: On a flat-bed scanner the map is placed on a flat scanning stage and the detectors
move across the map in both the X and the Y directions (similar to copy machine).

Drum scanner: On a drum scanner, the map is mounted on a cylindrical drum which rotates while
the detector moves horizontally across the map. The sensor motion provides movement in the X
direction while the drum rotation provides movement in the Y direction.

The output from the scanner is a digital image. Usually the image is black and white but scanners
can record color by scanning the same document three times using red, green and blue filters.

Inputting existing digital files: There are many companies and organizations on the market that
provide or sell digital data files often in a format that can be read directly into a GIS. These digital
data sets are priced at a fraction of the cost of digitizing existing maps.

Over the next decade, the increased availability of data should reduce the current high cost and
lengthy production times needed to develop digital geographic data bases.