Map display apparatus

Abstract

A vehicular navigation system for displaying map data generated by assuming that an area surrounded by particular longitudes and particular latitudes is a rectangle or a square, and for adequately correcting distortion of map with restricting a decrease of a map drawing speed. A vehicular navigation system determines a distortion correction coefficient Hs at a detected present position, and generates a coordinate conversion correction coefficient table Ht by multiplying the distortion correction coefficient Hs by a sine value of a rotation angle. While drawing the map, the system converts map data by using the coordinate conversion correction coefficient table Ht. The coordinate values X and Y after conversion can be respectively calculated by X=βx−αy, Y=αx+βy, by using the coordinate conversion correction coefficient α with respect to the sine value of the rotation angle θ in the map and the coordinate conversion correction coefficient β with respect to the cosine value of the rotation angle θ in the map. As a result, the number of multiplications is reduced. Then it can adequately correct the distortion of the map by restricting a decrease of a map drawing speed.

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