This paper describes a cheap, portable coordinate system for measuring circular geometries. The developed software can measure diameters, circle center coordinates, and distances between them. The circle detector uses the Adaptive Hough Transform implemented in the OpenCV library. For image rectification, the system uses reference circle positions on the plane parallel to the plane of the measured ones. Pixel size is determined by the distances between the reference circle positions on the same plane. The mean measurement value from a series of photos was found efficient estimation of accurate value, significantly improving overall system accuracy.