Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2001-02-01
2002-07-23
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S209000, C340S988000, C340S990000, C340S995190
Reexamination Certificate
active
06424911
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an intersection display method, and a map display unit and a recording medium for realizing this method. More particularly, the present invention relates to a method for displaying an intersection shape employed in map display units represented by vehicle-mounted navigation systems and portable navigation systems, a map display unit employing this method, and a recording medium containing a computer program or data for executing this method.
2. Description of the Background Art
Initially, in map display units such as navigation systems, a road network map using nodes and links to represent intersections and roads respectively was generally displayed on a screen upon request of the user.
In such a road network map, roads (links) were not provided with their widths. Therefore, the user found difficulty in intuitively understanding a node on the map as an intersection. Moreover, this type of map failed to display detailed road information, such as the number of lanes and lane regulations, relating to actual intersections and junctions (hereinafter, these are collectively called “intersections”).
In recent years, in order to overcome the above problems, there have been developed various navigation systems employing a method for displaying a map provided with road widths. That is, road links are displayed in the shape having widths corresponding to the actual road widths, so as to present a map including roads closer to the actual roads in shape. According to the conventional method for displaying a map provided with road widths, road shapes having widths corresponding to the actual road widths are generated based on road links, and placed overlapping each other. In this method, the overlap portion of all the width-imparted roads connected to one node is considered as an intersection for convenience.
As a conventional map capable of providing intersections for convenience, usable is a town map constructed of geometries of buildings and blocks. In such a town map, portions other than buildings and blocks can be recognized as roads. Therefore, by using a town map, an intersection can be displayed in a shape considerably close to the actual shape.
The conventional method for displaying a map provided with road widths described above has the following problems. This method simply considers the overlap portion of width-imparted road links as an intersection shape for convenience. That is, this method does not generate an actual intersection shape. Therefore, the intersection shape for convenience greatly differs from the actual intersection shape in many cases.
In addition, in the conventional method for displaying a map provided with road widths, since the actual intersection shape is not recognized, it is very difficult to specify the positions at which accessories in and around an intersection (crosswalks, stop lines, an island in the center of a rotary, and the like) are to be placed.
Moreover, in the conventional method for displaying a map provided with road widths, a problem arises when a driving path is to be displayed in an intersection along a route searched based on the road network. That is, since the actual intersection shape is not determined, a driving path can only be drawn as a path passing through the node (intersection) of the original road network. Therefore, a smooth driving path cannot be drawn for a right or left turn at the intersection.
The conventional method using a town map for recognizing an intersection shape has the following problem. It takes a huge amount of time to collect nationwide detailed town map data. In reality, therefore, town maps of only limited areas are collected. If nationwide town map data is successfully collected, the resultant data amount will be enormous. It is difficult to store such nationwide town map data in a map display unit having a small memory capacity, a map display unit that receives map data via communications, and the like.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide an intersection display method for generating and displaying an intersection shape by use of a road network map having a degree of scale higher than a town map, and a map display unit and a recording medium for realizing this method.
The present invention has the following features to attain the object above.
A first aspect of the present invention is directed to an intersection display method for generating and displaying an intersection shape by use of map data including a road network. The method includes the steps of:
reading from the map data an intersection node representing an intersection and intersection-connected links representing roads connected to the intersection node, constituting the road network;
generating an intersection shape at the intersection node and width-imparted intersection-connected links, based on the intersection node and the intersection-connected links; and
displaying the intersection shape together with other information for guidance notification.
As described above, in the first aspect, an intersection shape is generated with reference to a road network included in map data. This allows for display of an intersection shape closer to the actual shape. In addition, the amount of map data required can be smaller compared with the case of generating an intersection shape using a town map.
Preferably, the step of generating an intersection shape includes:
generating a width-imparted intersection-connected link by specifying a road width of each of the intersection-connected links based on information associated with the intersection-connected link, and drawing side lines representing edges of the road on the right and left sides of the intersection-connected link based on the specified road width; and
sorting the positions of the intersection-connected links based on the bearings at which the intersection-connected links are connected to the intersection node.
Thereafter, the following technique may be adopted.
The technique includes: determining cross points each between inner side lines of every two adjacent width-imparted intersection-connected links, and determining lines extending orthogonal to the intersection-connected links at positions outside the cross points with respect to the intersection node; and
determining cross points between the lines and the side lines, and connecting the cross points in the order of the sorted intersection-connected links to form a polygon as the intersection shape.
By the above technique, the width-imparted road links and the lines defining the intersection shape cross at right angles. Therefore, the vehicle stop position at the intersection is explicitly determined, and the resultant intersection shape is closer to the actual shape.
Alternatively, the technique may include: determining cross points each between inner side lines of every two adjacent width-imparted intersection-connected links, and connecting the cross points in the order of the sorted intersection-connected links to form a polygon; and
determining new points by shifting the cross points as the vertexes of the polygon by a predetermined distance along the side lines crossing at the respective vertexes outward with respect to the intersection node, and connecting the new points in the order of the sorted intersection-connected links to form a new polygon as the intersection shape.
The overlap portion of the width-imparted road links itself is not used as the intersection shape, but is expanded by shifting the vertexes of the portion outward with respect to the intersection node, to increase the number of corners of the intersection shape. The resultant intersection shape is closer to the actual shape.
Alternatively, the technique may include: determining cross points each between inner side lines of every two adjacent width-imparted intersection-connected links, and connecting the cross points in the order of the sorted intersection-connected links to form a polygon; and
generating a predetermined ci
Ata Teruaki
Hamada Hiroyuki
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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