16. A printing system for detecting motion quality error of printed documents comprising: a print engine configured to print a document having text lines comprising a plurality of characters; a scanning device configured to scan the printed document and to generate a scanned image having the text lines and the characters; and a processor configured to: determine the orientation of the text lines in the scanned image with respect to a process direction of the printing system; detect positions in the process direction of the printing system of one of the text lines and the characters in the scanned image; determine position errors in the process direction in the printed document based on the detected process direction positions of one of the text lines and the characters in the scanned image and the determined orientation of the text lines; determine at least one motion quality error of the printing system in the process direction based on the determined process direction position errors; and initiate an activity associated with the printing system in response to a motion quality error having been determined.
16. A printing system for detecting motion quality error of printed documents comprising: a print engine configured to print a document having text lines comprising a plurality of characters; a scanning device configured to scan the printed document and to generate a scanned image having the text lines and the characters; and a processor configured to: determine the orientation of the text lines in the scanned image with respect to a process direction of the printing system; detect positions in the process direction of the printing system of one of the text lines and the characters in the scanned image; determine position errors in the process direction in the printed document based on the detected process direction positions of one of the text lines and the characters in the scanned image and the determined orientation of the text lines; determine at least one motion quality error of the printing system in the process direction based on the determined process direction position errors; and initiate an activity associated with the printing system in response to a motion quality error having been determined. 26. The system according to claim 16 , wherein the processor is configured to filter out position variations due to image-content.