Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2000-11-06
2003-12-09
Louis-Jacques, Jacques H. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S208000, C701S211000, C340S990000, C340S995130, C340S995190, C340S995230, C342S457000, C342S357490
Reexamination Certificate
active
06662105
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a navigation device mounted on a mobile body for executing route guidance, and in particular to a navigation device which can obtain route data from an outside information center.
2. Description of the Related Art
A navigation device is known for executing route guidance in a vehicle. The navigation device includes a current position detecting section such as a GPS device and a map database. The navigation device recognizes the current position of the vehicle on a map and displays this information on a display. The navigation device also searches, upon inputting a destination, the best route from the current position to the destination. Moreover, if the route is set while the vehicle is traveling, the navigation device gives guidance such as turning right or left at an intersection, in addition to displaying the route on the display.
Some of the navigation devices communicate with an outside information center to obtain information such as congestion information. Furthermore, a system is being proposed in which the navigation device communicate with an outside information center to request a route search and obtains the search result.
By using the outside information center as described above, the navigation device can execute route guidance based on more precise road information.
In the navigation device, the current position detected by the current position detecting device such as the GPS device and the data for road positions in the map data are not particularly precise. Because of this, when the detected current position is marked on a map display based on the map data, there are cases where the display is not accurate.
The vehicle, on the other hand, usually travels on a road. This allows for a process called map matching, in which the trajectory of the current positions is compared with the map data to compensate the position of the vehicle on the map. In this manner, the current position can be moved onto a road and can be accurately displayed.
As described above, by requesting a route search to the information center, a more precise route search result can be obtained. However, in order to communicate with the information center, lines such as a telephone line must be used, and thus, the operation involves some communication cost. Moreover, there are cases where the information center applies fees to its service. Therefore, a cost is incurred for requesting a route search to the information center. In addition, because the mobile body communication usually uses wireless communication, there are cases where sufficient communication cannot be achieved due to the receiving environment for the electric wave.
The map matching is performed with an assumption that the map data is correct. However, road construction is continuously being performed, and when the map data becomes old, the vehicle may travel on a road that is not present in the map data. In such a case, the map matching cannot be correctly performed, resulting in failure to detect the current position.
SUMMARY OF THE INVENTION
One of the objects of the present invention is to provide a navigation device which takes advantage of a route search by an information center and which can improve the precision of a map matching process.
According to one aspect of the present invention, there is provided a navigation device mounted on a mobile body for executing route guidance, the navigation device comprising a mobile body route searching device for conducting route search using a map database maintained at the device to obtain route guiding data, an information center route searching device for obtaining route guiding data from an information center using wireless communication, and a search selecting device for determining whether to use the mobile body route searching device or the information center route searching device. In this manner, according to the present invention, a search selecting device is included for allowing selection of the searching device. A suitable searching device can be selected according to various conditions to obtain an accurate route search result while maintaining a suitable communications cost and responsiveness.
It is preferable that the search selecting device selects whether to use the mobile body route searching device or the information center route searching device based on the condition of the optimal route at the route search. For search selection, there are many conditions such as whether search should be conducted with higher priority on highways or on the distance. There are cases where the decision as to whether the mobile body or the information center is more suitable for search can be determined from particular conditions. By considering these conditions for route search, a suitable search device can be selected.
It is also preferable that the route is searched on a plurality of conditions for an optimal route and the search selecting device determines the route searching device for each of the plurality of conditions. By searching on a plurality of conditions, the user can be notified of the optimal route for each condition, and can select the route set from these conditions. By determining the searching device considering factors such as the search load, all the search result can be quickly obtained.
It is also preferable that the route search includes at least a peripheral route search for returning to a set route when off-route, in addition to a complete route search for searching routes to the destination, and the search selecting device determines the route selecting device based on the type of search. The peripheral search may be conducted many times in the case of going off-route or the like. If the search is requested to the information center for each peripheral search, it is likely that the cost will be increased. Moreover it is usually true that the peripheral search needs a quick result, and thus, search at the mobile body is desirable because search can be quickly conducted without spending time to establish a line. Therefore, it is preferable to determine the searching device based on the type of search.
It is also preferable that the search selecting device determines the route selecting device to be used based on the version of the map data in the map database maintained at the navigation device. If the version at the information center is more recent than the version at the mobile body, it is unlikely that the map database at the mobile body will hold accurate road data. Because of this, it is preferable to decide whether or not to request search to the information center considering the version.
It is also preferable that the search selecting device determines a route searching device to be used based on the date when the map data is generated, in the map database maintained at the navigation device. If the date of generating the map is not recent, reliability of the map is decreased and it is thus preferable to select a searching device considering the date when the data was generated.
It is also preferable that the search selecting device divides the route search into two portions, one with the distance to the destination large and the other with the distance to the destination small, and selects the route searching device. It is usually the case that a search result for roads near the current position is needed quickly and that the device should not establish communication. It is also true that the congestion information etc., near the current position can be sufficiently obtained at the mobile body. Therefore, the search for the roads near the current position can often be performed by the mobile body. By considering this point, a suitable searching device can be selected.
It is also preferable that the route selecting device decides the route searching device to be used using operation schedule information of the information center. When the information center is not operated, a search cannot be requested. Therefore, by not communicating in such a case, ineffecti
Sugimoto Hironobu
Tada Akihito
Yurimoto Masayuki
Louis-Jacques Jacques H.
Oliff & Berridg,e PLC
Toyota Jidosha & Kabushiki Kaisha
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