This paper presents a global localization method based map matching. A local map is built by uccessive splitting and merging scan points. A global map is built by merging all local maps. Local and global map are represented line segments that are sorted counterclockwise. Complete line segments are selected to match between two maps. Matching is based on relative position relation complete line segment. Localization algorithm based ordinal map and based on relative position relation improves matching efficiency and lowers computational cost. All these techniques have been implemented on mobile robot ATRVII equipped with 2D laser scanner SICK.