Patent 7831383 was granted and assigned to Denso on November, 2010 by the United States Patent and Trademark Office.
A highlight display flag is assigned to a link datum having undergone addition or modification when road map data are updated. A road corresponding to a link datum assigned with the highlight display flag is displayed in a highlight display form. When the highlight display form for the corresponding road is determined to be unnecessary in consideration of (i) an elapsed time period posterior to the update or (ii) a cumulative display time period, the highlight display form is returned to a usual display form.