In order to obtain a compact and exact representation of 2D range scans, UKF (unscented Kalman filter) and CDKF (central difference Kalman filter) were proposed for extracting the breakpoint of the laser data. Line extraction was performed in every continuous breakpoint region by detecting the optimal angle and the optimal distance in polar coordinates, and every breakpoint area was constructed with two points. As a proof to the method, an experiment was performed by a mobile robot equipped with one SICK laser rangefinder, and the results of UKF/CDKF in breakpoint detection and line extraction were compared with those of the EKF (extended Kalman filter). The results show that the exact geometry of the raw laser data of the environments can be obtained by segmented raw measurements (combining the proposed breakpoint detection approach with the line extraction method), and method UKF is the best one compared with CDKF and EKE.