The principle of three-coordinate detection is to put the measured object in the measuring space of three-coordinate measuring machine, accurately measure the values of points on the surface of the measured part at three coordinate positions in space by using contact or non-contact detection system, and then fit the spatial coordinate values of these points to form measuring elements, such as circles, spheres, cylinders, cones, curved surfaces, etc. The geometric size, shape and position to be measured are calculated by software.

The measuring function of three coordinates should include dimensional accuracy, positioning accuracy, geometric accuracy and contour accuracy.

Three coordinates have no special requirements for the measured object, and different probes and needles should be selected according to the measured object when measuring.