MAP DISPLAY CONTROLLER

PROBLEM TO BE SOLVED: To simplify the calculation of coordinate transformation for rotating/ displaying a road map and to speed up a display processing. SOLUTION: A storage means 3 storing road map data, a display means 1 displaying a road map on a screen and a display control means having a coordinate transformation means reading road map data stored in the storage means and transforming a coordinate corresponding to the screen and developing the road map displayed on the display means are installed. In the case of road map data constituted of plural divided cells, the coordinate transformation means obtains XY direction components at the time of transformation into coordinates in screens left-below, right-below and left-above the cell and coordinates in the screens at a lower side and a left side or obtains the coordinates left-below and right-below the screen on road map data and the XY direction component of the lower side and the respective points of the cell are coordinate-transformed based on the screen coordinate left-below and the XY direction component.