1. A document scanning method comprising the steps of causing relative movement between a document and first and second imaging elements, such that each of a succession of scan lines of the document is exposed in turn to the imaging elements; generating by means of the first and second imaging elements respective first and second image data words representative of respective first and second overlapping portions of each scan line; and concatenating at least a portion of each of the first and second words to generate a third image data word representative of the scan line, the method being characterised by the steps of cross-correlating at least a portion of each of the first and second words to identify a portion of the second word that is included in the first word; discarding a portion of at least one of the first and second words; concatenating the first word or remainder thereof with the second word or remainder thereof to form the third image data word; and, if necessary, compressing or expanding the third word by linear interpolation so as to obtain an image data word of a predetermined length.