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Recognition of character strings from color urban map images on the basis of validation mechanism

Map recognition is one of the most interesting methods to distinguish meaningful information automatically from map images and to construct resource data in information systems such as GISs (geographic information systems). However, it is difficult to identify individual pieces of information because the map components mutually intersect or are overlayed, and because the properties of the map components are not well defined. In this paper, we propose a method of extracting character strings from color urban map images. The characteristic of our method is to validate the identified character strings with map composition rules. Our recognition process is composed of two phases: extraction of character strings and classification of character strings. The extraction phase is organized by a bottom-up approach, based on measurement/estimation among pixels, while the classification phase is composed by means of a top-down approach, based on interpretation/validation among map components.