| 摘要 |
PURPOSE: To shorten the plotting time of road maps by converting the road maps of respective stored hierarchies into the road maps of a birds's-eye view system and plotting these road maps in superposition. CONSTITUTION: Road map data are previously stored on a CD-ROM 8 by classifying the data to the three hierarchies; broad road map data consisting of wide- area information corresponding to the wide range on the road maps, intermediate road map data consisting of intermediate information corresponding to the intermediate range on the road maps, and wide-area road map data consisting of the wide-area information corresponding to the narrow range on the road maps. The road map data of the respective hierarchies are converted into the road maps of the birds's-eye view system and the converted road maps of the birds's-eye view system of plural hierarchies are plotted in superposition on the display 10. As the result, the need for processing to rearrange the boundary parts on the display screen plotted by the road maps of the different hierarchies is eliminated and the time for plotting the road maps is shortened. |
