US Patent 7315360 Surface coordinate system

A method for creating a reference for a first position on a substrate edge. A first reference point is selected relative to a circumference of the substrate edge, and a second reference point is selected relative to a bevel of the substrate edge. A first distance along the circumference of the substrate edge between the first reference point and the first position is identified as a first coordinate, and a second distance along the bevel of the substrate edge between the second reference point and the first position is identified as a second coordinate. The first coordinate and the second coordinate are used as the reference for the first position.