Robust algorithm for determining line centre within a video positional measuring system

The paper presents research into line centre detection using a video positioning system, as part of a measuring system for line scale calibration. In the described approach, the video positioning system processes an image taken by a CCD camera to estimate the position of the observed line's centre. An important part of this research is also an analysis of line scale contamination's influence (scratches, dirt, usage, etc.) on line position determination. The outcome of the research is mathematical models that can be used as a base for developing a positioning algorithm. This algorithm is simple and adaptable to different types of line scales. It also includes a module for increasing the basic scale factor of the positioning as defined by the number of pixels in the CCD sensor, and a module for reducing the influence of contamination on positioning.