Abstract: The present invention enables the computation of various types of information for a particular scanned and OCR recognised or retyped historical input document. It provides a global view on the “patterns” for historical language variation (text profiling) and the OCR errors most frequently found in the text (error profiling). For each of the individual tokens of the OCR output, an interpretation is given which based on the document specific information attempts to describe both, the underlying correct word of the text and the corresponding modern spelling of the word. This not only provides input for optimised OCR recognition of historical documents, but also for quality assurance and improved information retrieval.