Transforming schematics to CAD files using a Hough-based recognition scheme

An integrated system for converting scanned schematics into computer-aided-design files is presented. An investigation is made into the recognition of all electrical engineering symbols recommended by the IEE. Symbol recognition employs an enhanced Hough transform representation complemented by a feature selection process which takes place under decision tree control. Character recognition is carried out by a dynamic implementation of the Ross template matching scheme. It is recognized that the close similarities of many components and ambiguities in the data, had to be resolved by human interaction. A post-processor error correction plan is therefore proposed to improve the performance of the system. Tracking of the interconnections is carried out to obtain a directed graph representation of the circuit diagram which is subsequently analysed to produce the CAD file