POLYGON LOOKUP METHOD

A conversion unit (15b) converts a polygona rea within a predetermined unit area on a map into polygonal information (14b) indicated using coordinates of vertexes of the polygonal area and stores the polygonal information (14b) in a storage unit (14) in association with the unit area. A specifying unit (15c) specifies temporospatial information (14c) including positional information corresponding to coordinates within the predetermined unit era on the map. An extraction unit (15d) extracts the temporospatial information (14c) including positional information corresponding to coordinates inside a polygona area indicated with the polygonal information (14b) associated with the unit area among the specified temporospatial information (14c).