Extraction of valid data sets in registers using recognition of invalidation lines

摘要

This paper describes an approach for the extraction of the valid data sets in legal registers containing data which have been invalidated by invalidation lines. Invalidation lines are hand drawn lines below the invalid words or text lines. In a first step detection of horizontal lines and segmentation of the text objects (block, line, word, character) is performed based on a fast connected component analysis using sub-components, which is robust against touching lines. Invalidation is performed on a word or text line level using the neighborhood relation between text objects and invalidation lines. Invalidations are recognized with about 90% accuracy at about 10% rejection threshold (false negatives). The error rate (i.e. invalidation of a valid word) is less than 0.5%. For most data sets it is sufficient to eliminate the invalidated text, so the valid data remains. In a second step a syntactical analysis on the valid text strings is performed. This increases the accuracy to 99% on the data set level. Error detection and correction is done by a graphical user interface. Data capture time can be reduced by a factor of 2 to 3 compared with manual input.