Digitizers:

A common device for, painting, drawing or interactively selecting coordinate positions on an object is a digitizer. These devices may be utilized to input coordinating values in either a two-dimensional or a three-dimensional space. Typically, a digitizer is utilized to scan over a drawing or object and to input a set of discrete coordinate positions, which may be joined with straight-line segments to approximate the curve or surface shapes.

One type of digitizers is the graphics tablet (also referred to as a data tablet) which is utilized to input two-dimensional coordinates by activating a hand cursor or stylus at selected positions on a flat surface. For sighting positions a hand cursor contains cross hairs, when a stylus is a pencil-shaped device that is pointed at location on the tablet. Tablet size varies from 12 by 12 inches for desktop models to 44 by 60 inches or larger for floor models. Graphics table provide a highly accurate method for selecting coordinate positions, with an accuracy that varies from around 0.2 mm on desktop models to about 0.5 mm or less on longer models.

Various graphics tablet are constructed with a rectangular grid of wires embedded in the tablet surface. Electromagnetic pulses are produced in sequence along the wires, and an electric signal is involved in a wire coil in an activated stylus or hand cursor to record a tablet position. Based on the technology, signal strength, coded pulses, or phase shifts may be utilized to determine the position on the tablet.