Method and apparatus for storing cartographic route data

Abstract

A method and device implementing a three-level hierarchy for storing, recalling and processing navigational and graphical data. A vehicle is equipped with an electronic navigation thoroughfare planning device capable of calculating the distance to a desired thoroughfare. To calculate a distance, a driver inputs a plurality of variables, including cartographic data and a final desired destination, as well as several potential additional variables. Upon receiving the driver inputs, the navigation device implements a three-level hierarchy for storing, recalling and processing cartographic data. After the cartographic data is stored in memory, the navigation unit can calculate distance to a thoroughfare utilizing a cascading search method beginning with searching the most specific first level and progressing to the broader second and third levels until a common network between the two locations is established. The navigation device can also utilize the three level hierarchy to display cartographic data as a graphical map on the unit utilizing the same cascading method to display detail on the display screen and locate the specific details on any coordinate on the screen. Therefore the navigation unit utilizes the same three level hierarchy to calculate distance to a desired destination and to display a graphical representation of the map.