an illustration of a data structure according to which road map data is stored in a memory; FIGS. 6A and 6B are a flow diagram describing the steps required to display a road map according to the invention; FIG. 7 is a flow diagram of a timer operation associated with FIGS. 6A, 6B; FIG. 8 is a sketch illustrating the method of accessing a desired location of a road map to provide a landmark thereo