Circle fitting based position measurement system using laser range finder in construction fields

In this paper, an accurate long-distance position measurement system using laser range finders (LRFs), which can be used for surveys in construction fields is proposed. Since the LRF is a sensor which can measure distance to surfaces of objects by radiating laser beams from itself and receiving the reflected ones, data obtained from the LRF are nothing more than the contours of objects. For this reason, we adopted cylindrical shaped objects since the contour, a circular arc, is invariant against rotation. Therefore, this research aims to fit circles to the arc-shaped contours of the cylindrical objects and estimate their accurate center positions by applying the least square method and maximum likelihood estimation. If we know the radius of the cylindrical object in advance, the aforementioned two methods become non-linear problems. For this reason, we applied the Newton-Raphson method to solve these non-linear equations. We improve the angular resolution of the LRF by using a pan unit, and reveal that the maximum likelihood estimation can give us the most accurate center position. Additionally, we implemented proposed position measurement system in an actual construction field.