Road area extracting apparatus for extracting a road area from a block map, deformed map automatic generation system for generating a deformed map from road area data obtained by the road area extracting apparatus, map information providing system, geographical information providing system and geographical information describing method

A road area extracting apparatus comprising:

• receiving means for receiving an image drawing region;
• block information reading out means for reading out pieces of particular block information corresponding to the image drawing region received by the receiving means from a block map data base in which pieces of block information respectively indicating a line segment row and each line segment divides a block area from a road area, a plurality of particular line segment rows indicated by the pieces of particular block information respectively having an end placed at a boundary line of the image drawing region, in which said block map data base stores line segment rows each being composed of a plurality of straight line segments connected with each other in series and the road area being represented by a pair of line segment rows spaced from each other with a clearance corresponding to a road width;
• road shape extracting means for setting each point, at which one end of one particular line segment row indicated by one piece of particular block information contacts with the boundary line of the image drawing region, as a boundary point, selecting a pair of boundary points close to each other and connecting the pair of boundary points with each other through a connecting line segment to extract a shape of a road area surrounded by the connecting line segment and a pair of particular line segment rows connected with the connecting line segment from the particular block information read out by the block information reading out means;
• and
• road area outputting means for outputting the shape of the road area extracted by the road shape extracting means as an areal and configurational road having the road width defined by said pair of particular line segment rows and a longitudinal road edge defined by the connecting line segment.