1. To translate graphical information into a series of numbers suitable for processing by (digital) computer. For example, topographic detail can be taken from a map and digitized to produce a computer-generated topographic cross-section. The superimposition of an orthogonal coordinate system on to an image and the recording of the data in a machine-readable form assumes that a two-dimensional image is being analysed. It can be done three- dimensionally if stereophotographs are analysed. Fully automated systems also exist for this type of work.

2. To convert analog data into digital form by sampling the continuous record at discrete sample intervals. See also aliasing; sampling frequency.