x1 is at position or in direction x2 (referenced by clock positions) relative to oriented viewer x3 along circumference x4 (default when applicable: the natural horizontal of x3 or, if none exists, the horizon) and using angle measurement system x5 (default: twelve-hour clock which clicks clockwise as viewed from above).
x3 specifies the central point or vertex of the angle as well as the forward direction from which the angle is measured (which, for default x5, is the 12 o'clock or 0 o'clock position).