Map data transmitting method, map data transmitting apparatus, information device and map data transmitting system

DETAILED DESCRIPTION The present invention provides a map data transmitting technology that allows polygon data corresponding to an area ranging beyond the slicing range to be transmitted in an appropriate form.
(1) A map data transmitting method according to the present invention comprises steps of; setting a specific route, specifying map data contained in a slicing range within a predetermined distance from the route having been set based upon map data that include road data and background data, newly creating a new polygon data if an original polygon data contained in the background data included in the specified map data is partially contained in the slicing range and another portion of the original polygon data is outside the slicing range, by removing polygon data corresponding to the portion outside the slicing range from the original polygon data and transmitting a road map specified in corresponding to the map data and background data containing the new polygon data.
(2) In this map data transmitting method, in the transmitting step, either the original polygon data or the new polygon data may be transmitted based upon the difference between the data volume of the original polygon data and the data volume of the new polygon data or the a real ratio of the two types of data.
At this time, if the new polygon data are transmitted, information indicating that the new polygon data are transmitted should be appended to the transmission data.
(3) It is to be noted that the route set in the map data transmitting method described above may be a recommended route calculated based upon the current point and a destination.
(4) A map data transmitting apparatus according to the present invention executes the map data transmitting method described above.
(5) An information terminal according to the present invention comprises a reception unit that receives map data transmitted from the map data transmitting apparatus and a display unit that displays a map based upon the map data having been received