1. A method of correcting digitized map data provided by a map data supplier and stored in a map database of a navigation device, the map data comprising routing data in the form of route links and shape points, wherein each route link is associated with a sequence of shape points representing a course of a road segment for display on a screen, the method comprising the steps of: switching to an editing mode indicating to the user that at least one of displayed road segments and/or shape points can be graphically manipulated on the screen and providing to the user a map data correct reference by displaying a current user position on the screen without matching the user position to the nearest neighboring road segment of the displayed road network by setting a matching algorithm inactive; detecting a first user input operation indicative of a selection of a road segment displayed on the screen; displaying on the screen, based on the map data provided by the map data supplier, at least one existing shape point of the sequence of shape points stored in the map database for the selected road segment; detecting at least one second user input operation indicative of a graphical manipulation of the course of the selected road segment on the screen, wherein the graphical manipulation comprises a positional displacement of at least one existing shape point of the sequence of shape points displayed on the screen by shifting the at least one existing shape point from the displayed screen position to a new screen position; generating on basis of the detected second user input operation corrected routing data reflecting the manipulated course of the selected road segment; and storing the corrected routing data in the map database by overwriting the existing routing data of the selected road segment by the generated corrected routing data without modifying a structure of the original map database provided by the map data supplier, wherein the corrected routing data in the map database is subsequently employed for one of a route guidance process, a map displaying process and a map matching process.