Polar coordinate system
In the Cartesian coordinate system a point is described, for instance, by its X and Y coordinates. For rotation
symmetrical contours, such as circular boring patterns, calculating the needed coordinates requires extensive
computing.
In the polar coordinate system a point is specified by its distance (radius r) to the point of origin and its angle
(a) to a specified axis. The angle (a) refers to the X axis in the X,Y coordinate system. The angle is positive,
if it is measured counterclockwise starting from the positive X axis (see figure 18). In the opposite direction it
is negative (see figure 19).