Automatic Extraction of Direction Information from Road Sign Images Obtained by a Mobile Mapping System

Road signs are crucial infrastructures for safe driving. For systematic management of road signs, construction of a road sign database and implementation of a road sign management system are essential for local governments. In this paper, we deal with automatic extraction of direction information from road sign imagery obtained by a mobile mapping system. Our approach starts with image pre-processing and binarization. Next, arrow regions are extracted by the proposed four-direction contiguous pixel measures, so called line scan method. Corner points are detected by using a “good features to track” algorithm based on an extended Newton–Raphson method. Some of the detected corner points clearly show the arrow heads. Lastly, a least squares matching (LSM) algorithm is applied to the corner points to extract direction information. For the LSM algorithm, eight directional arrow head shape templates are used. As a result, we can automatically extract direction information from road sign imagery.