Map data creating device, navigation device, and map processing system using these devices

1. A map data creating device comprising:

a map database for storing map data;

a route searching unit for searching for a prospective travel route comprising a plurality of links, the prospective travel route leading from a place of departure to a destination and being described by searched route data;

an average travel speed calculating unit for calculating an average travel speed for each link included in the searched route data based on information which is included in the map data acquired from said map database and which is assigned to a corresponding link;

a control unit for dividing the prospective travel route which is searched for by said route searching unit into sub-routes according to the average travel speeds calculated by said average travel speed calculating unit to acquire map data about maps for the respective sub-routes from said map database, the scale of each of said maps being determined according to one of the calculated average travel speeds associated with the corresponding sub-route; and

a searched route data storage unit for storing the map data acquired by said control unit while bringing the map data into correspondence with said each of the sub-routes.

2. The map data creating device according to claim 1 , wherein the searched route data storage unit stores map data about a map of an area including a start point, an end point, and all waypoints of each of the sub-routes as the map data associated with said each of the sub-routes.

3. The map data creating device according to claim 1 , wherein the route searching unit searches for a plurality of routes from the place of departure to the destination, the average travel speed calculating unit calculates an average travel speed for each link included in searched route data showing each of the plurality of routes which are searched for by said route searching unit based on information which is included in the map data acquired from the map database and which is assigned to a corresponding link, the control unit divides each of the plurality of routes which are searched for by said route searching unit into sub-routes according to the average travel speeds calculated by said average travel speed calculating unit to acquire map data about maps for the respective sub-routes from said map database, the scale of each of said maps being determined according to one of the calculated average travel speeds associated with the corresponding sub-route, and the searched route data storage unit stores map data about a map of an area including all of a start point, an end point, and waypoints of each of the sub-routes of each of the plurality of routes which are searched for by said route searching unit as map data associated with said each of the sub-routes.

4. The map data creating device according to claim 1 , wherein the control unit divides the route which is searched for by the route searching unit into sub-routes according to the average travel speeds calculated by the average travel speed calculating unit, and acquires from the map database map data about a map including a connection point at which two contiguous sub-routes are connected with each other, the map having a scale different from scales according to average travel speeds for the two contiguous sub-routes acquired through said division.

5. The map data creating device according to claim 1 , wherein said map data creating device includes a display unit for outputting information, the route searching unit searches for a plurality of routes, the average travel speed calculating unit calculates an average travel speed for each link included in the searched route data showing each of the plurality of routes which are searched for by said route searching unit based on information which is included in the map data acquired from the map database and which is assigned to a corresponding link, the control unit divides each of the plurality of routes which are searched for by said route searching unit into sub-routes according to the average travel speeds calculated by said average travel speed calculating unit to acquire map data about maps for the respective sub-routes from said map database, the scale of each of said maps being determined according to one of the calculated average travel speeds associated with the corresponding sub-route, the searched route data storage unit stores map data about a map of an area including all of a start point, an end point, and waypoints of each of the sub-routes of each of the plurality of routes which are searched for by said route searching unit as map data associated with said each of the sub-routes, and said display unit outputs information enabling determination of whether or not a transfer between sub-routes of the plurality of routes can be performed.

6. A navigation device comprising:

a current position detecting unit for detecting a current position and a current travel speed;

an external data acquiring unit for acquiring searched route data showing a prospective travel route which is searched for and which is divided into a plurality of sub-routes according to average travel speeds calculated for each link included in the prospective travel route based on information included in an external database, and map data about maps corresponding respectively to said plurality of sub-routes, the scale of each of said maps being determined according to one of the calculated average travel speeds associated with the corresponding sub-route; and

a control unit for performing a process of displaying from said acquired map data the map corresponding to a particular one of said plurality of sub-routes in which said detected current position is located, to guide a user along said searched route.

7. A map processing system comprising:

a map data creating device; and

a navigation device,

wherein said map data creating device includes:

a map database for storing map data;

a route searching unit for searching for a prospective travel route comprising a plurality of links, the prospective travel route leading from a place of departure to a destination and being described by said searched route data;

an average travel speed calculating unit for calculating an average travel speed for each link included in the searched route data based on information which is included in the map data acquired from said map database and which is assigned to a corresponding link;

a control unit for dividing the prospective travel route which is searched for by said route searching unit into sub-routes according to the average travel speeds calculated by said average travel speed calculating unit to acquire map data about maps for the respective sub-routes from said map database, the scale of each of said maps being determined according to one of the calculated average travel speeds associated with the corresponding sub-route;

a searched route data storage unit for storing the map data acquired by said control unit while bringing the map data into correspondence with said each of the sub-routes; and

an output unit for outputting data stored in said searched route data storage unit, and wherein said navigation device includes:

a current position detecting unit for detecting a current position and a current travel speed;

an external data acquiring unit for acquiring said searched route data outputted from the output unit of said map data creating device and map data; and

a control unit for performing a process of displaying a map having a scale corresponding to said current position and said current travel speed according to said searched route data and said map data to guide a user along said searched prospective travel route.