Abstract: A magnetic compass modified for use in linear, angular and, geometric as well as, or instead of, directional measure. Body (30), (35) manufactured to a predetermined circumference and made of a break-resistant material. Mounted on the base (33a) or, suspended from the top section (33b), is a freely pivoting or movable magnetic pointer (32) and a transparent, or partially transparent, upper section (35) so that the position of the pointer may be observed. Outer edge (31) made of slip-resistant material for contact and rotation on surface of structure being measured. Outer edge of base is calibrated with appropriate units positioned for use with pointer. Calibration (FIGS. 4a-c) could also possibly be inscribed on upper section of body instead of on the base. Most operations center around the locations of two variable points on the Compass Ruler, the contact point (37) and the zero point (36).