Symbol recognition using spatial relations

In this paper, we present a method for symbol recognition based on the spatio-structural description of a 'vocabulary' of extracted visual elementary parts. It is applied to symbols in electrical wiring diagrams. The method consists of first identifying vocabulary elements into different groups based on their types (e.g., circle, corner). We then compute spatial relations between the possible pairs of labelled vocabulary types which are further used as a basis for building an attributed relational graph that fully describes the symbol. These spatial relations integrate both topology and directional information. The experiments reported in this paper show that this approach, used for recognition, significantly outperforms both structural and signal-based state-of-the-art methods. (C) 2011 Elsevier B.V. All rights reserved.