With today's CMM software, the CMM measures the workpiece's datums (from the part print), establishes the Part Coordinate System, and mathematically relates it to the Machine Coordinate System.

The process of relating the two coordinate systems is called alignment (Figure 4). With a street map, we do this automatically by turning the map so that it is parallel to street (datum) or to a compass direction (i.e., north).  When we do this, we're actually locating ourselves to the "world's coordinate system".