Patent ID: 7076364
Filing Date: 2006-07-11
Classification: G01C,G09B

Abstract:
1. A road map display apparatus including a road map information memory for memorizing road map data on a two-dimensional coordinate, detection means for detecting a present position and a travel direction of an automotive vehicle, read-out means for reading out the two-dimensional coordinate of the road map data from said information memory in accordance with the present position and travel direction of the vehicle detected by said detection means, and image display means for displaying the read out two-dimensional coordinate in the form of a plane view on a screen, and parameter memory means for memorizing a plurality of trapezoid conversion parameters for display of a perspective view and a plurality of compression ratios in a y-axis direction; wherein coordinate conversion means is provided to contract a square two-dimensional coordinate at the upper side thereof in relation to the lower side thereof for converting the square two-dimensional coordinate to a trapezoid coordinate for display of a perspective view on a two-dimensional plane, said coordinate conversion means being arranged to compress the two-dimensional coordinate of the road map data read out by said read-out means for converting the compressed two-dimensional coordinate to the trapezoid coordinate, wherein said image display means is arranged to display the converted trapezoid coordinate in the form of a perspective view on the screen; and wherein said read-out means is arranged to expand a reverse trapezoid coordinate defined by the trapezoid conversion parameters at the memorized compression ratios and to read out a two-dimensional coordinate of the road map data included in the expanded reverse trapezoid coordinate from said road map information memory, and wherein said coordinate conversion means is arranged to compress the two-dimensional coordinate read out by said read-out means at the memorized compression ratios for converting the compressed two-dimensional coordinate to the trapezoid coordinate.