Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2000-03-29
2001-07-31
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S207000, C701S208000, C701S209000
Reexamination Certificate
active
06269305
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to navigation devices, more particularly to a navigation device of a type additionally advising a car which lane to take when guiding a way between any two locations arbitrarily designated on a map.
2. Description of the Background Art
A conventional navigation device commonly presents path information road by road to a driver. However, for safe and correct guidance of right/left turn at intersection or which road to take, path information road by road is not enough without information on lane change. This is because, even when the driver is on the right path, lane control may prevent him/her from heading for his/her destination, for example.
Accordingly, in recent years, various types of navigation devices capable of additionally guiding lanes have been developed. A typical conventional method of guiding lanes is lane graphical display. In this lane graphical display, for example, road link data directly linked to intersection nodes on a two-dimensional map is each manually provided in advance with the number of lanes and lane control information. When the car reaches a predetermined distance range of an intersection where the car is supposed to pass by, the lanes at the intersection are graphically displayed, and lane guidance information is also presented to the driver in accordance with the lane control information for the intersection.
The problem herein is, in the lane guidance information of the conventional navigation device, only path information and the number of lanes at the closest intersection are taken into consideration. Therefore, in a case where complicated-shaped intersections come along one after another, improper lane guidance information (i.e., lane change cannot be smoothly done) is often presented to the driver. This is because, for the driver to smoothly change lanes, it is not enough to concern about heading direction, the number of lanes, and lane control only at the closest intersection, but is necessary to concern about those at one or more intersections ahead. For example, when the car is on a three-lane road, and is supposed to go straight at the closest intersection and then turns left at the following intersection, it is easier for the driver to drive on a left lane to go along the path.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a navigation device of a type always offering proper lane guidance with consideration for circumstances not only at the closest but some more intersections ahead of the path.
The present invention has the following features to attain the object above.
A first aspect of the present invention is directed to a navigation device of a type guiding a car between any two locations arbitrarily designated on a map. In this navigation device, a guidance path between the two locations designated on the map is searched according to map data stored in a map data storage part. According to the map data, lane guidance information for the car about which lane to take on the guidance path is also generated. Moreover, according to the searched guidance path and the generated lane guidance information, guidance information relevant to path and lane is generated. Thereafter, the generated guidance information is outputted perceivably for a driver. The lane guidance information is generated in the following manner. First, the guidance path is divided at intersections so that the path is taken in as a plurality of between-intersection roads. Next, the between-intersection roads on the guidance path are selected one by one for a target between-intersection road, and the map data is referred to on the between-intersection road basis, whereby the selected target between-intersection road is determined by lane. Herein, reference to the map data for lane determination is kept on making, one by one, from the selected target between-intersection road to other between-intersection roads ahead on the guidance path until the target between-intersection road can be judged as being uniquely determined by lane. As is known from this, if reference to the corresponding map data is not enough to uniquely determine the target between-intersection road by lane, the map data corresponding to one or more between-intersection roads ahead on the guidance path is also referred to. In this manner, even when complicated-shaped intersections come along one after another in the limited range, lane guidance information relevant also to heading direction at one or more intersections ahead becomes available, and lane guidance can be carried out in a thoughtful manner for the driver.
The judgement whether or not the selected target between-intersection road can be uniquely determined by lane is made as follows. In detail, every time reference to the map data is made to any other between-intersection road located next, any exit lane ensuring the car of travel thereto is extracted from the between-intersection road one before. Then, when the number of extracted exit lanes is limited to one, it is judged that the target between-intersection road can be uniquely determined by lane. The exit lane determination accordingly leads to unique entry lane determination. Therefore, by tracing the extracted exit lanes from the between-intersection road lastly referred to back to the target between-intersection road, the target between-intersection road can be uniquely determined by entry/exit lanes.
In the present invention, preferably, an upper limit of reference frequency is predetermined with respect to the between-intersection roads, and when the reference frequency reaches its upper limit, reference to the map data is thus stopped. Thereafter, one exit lane ensuring travel to the between-intersection road located furthermost when reference to the map data is stopped is forcefully selected out of the exit lanes of the between-intersection road one before. In this manner, an endless loop for the lane determination processing can be prevented.
The map data may include both the between-intersection roads with the heading direction control set to the exit lanes and those without. If this is the case, the between-intersection roads without the heading direction control are detected so that default heading direction control is set to the exit lanes thereof. In this manner, every between-intersection road can be determined by lane.
The default heading direction control is provided in the following manner, for example. First, as to the between-intersection road without the heading direction control set, any branch road assumable to be straight-forward is specified among the ones connected thereto. Next, with reference thereto, the exit lanes of the between-intersection road without the heading direction control are each assigned to the branch roads. Herein, the branch road assumable to be straight-forward is the one whose connection angle with respect to the between-intersection road without the heading direction control is within a predetermined range, which shows the least difference in the number of lanes compared with the exit lanes thereof, and whose connection angle with respect thereto is closest to 180 degrees. In this manner, the branch road ensuring the smoothest travel is selected as the branch road assumable to be straight-forward. Herein, when the exit lanes of the between-intersection road without the heading direction control are each assigned to the branch roads, the method thereof may be changed depending on the number of branch roads connected thereto being larger or smaller compared with the number of exit lanes thereof. Accordingly, the heading direction control can be set in an elaborating manner.
A second aspect of the present invention is directed to a method of determining a lane for a car to take when the car is guided along a guidance path searched on map data. The lane determination technique used in the second aspect is substantially similar to the one described in the first aspect.
A third aspect of the present invention is directed to
Ata Teruaki
Sakamoto Kiyomi
Yamashita Atsushi
Cuchlinski Jr. William A.
Marc-Coleman Marthe Y.
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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