Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2001-05-23
2003-10-21
Cuchlinski, Jr., William A. (Department: 3663)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S213000, C701S209000
Reexamination Certificate
active
06636802
ABSTRACT:
TECHNICAL FIELD
The present invention relates to terminal devices, and more particularly to a terminal device for reading cartographic files from an internal storage device in which the cartographic files are stored as digital data generated about individual units defined by dividing a map into a plurality of regions.
BACKGROUND ART
(First Background Art)
Recently, an increasing number of vehicles are carrying navigation systems. Early navigation systems were only provided with files for generating maps on a screen (hereinafter referred to as cartographic files). However, recent models can be supplied not only with the cartographic files but also with traffic information and route guide information. Supply of such various information has made the car navigation systems so convenient that they are expected to rapidly prevail more and more.
The earlier navigation systems were equipped with storage devices having read-only storage media such as CD-ROMs. Cartographic files to be provided to users and their relevant data are previously recorded in the storage media. The storage devices read the cartographic files recorded in the storage media when necessary. The read cartographic files are referred to by the users, or used in route search or map matching process.
Generally, in order to efficiently manage a hierarchical structure of maps on different scales, a map is equally divided into rectangular areas in the longitude and latitude directions and a digital cartographic file is generated for each rectangular area. Now, in First Background Art, such a rectangular area is called a unit.
Such cartographic files are used in the car navigation systems typically for the route search process or process of correcting the present position (map matching). The cartographic files therefore contain road network data. The road network data is at least composed of connection information showing connections among nodes and links. Generally, a node is a piece of information which represents an intersection in the road network, and a link is vector information which represents a road between two intersections. A collection of such nodes and links expresses a map which shows the road network in each unit.
While minimum details of the road network can be represented with the nodes, links and their connection information, it is not enough for the purpose of displaying a map. For example, most roads in mountain or seaside areas are curved between intersections. Therefore the road network data further contains information for specifying the link shape to display curved roads. As is clear from this, the links are often represented by vector data.
Further, the roads include various types, such as national roads, prefectural roads, etc. The roads can be classified also according to the number of lanes, whether it has a median strip, etc. The road network data therefore also contains attribute information which shows the road type and the like.
Some intersections have their own names and others don't. Further, some intersections have traffic signals and others don't. Therefore the road network data further contains attribute information for each node. Each piece of the attribute information contains information showing the name of the intersection, presence/absence of traffic signals, etc.
When a road extends over a plurality of units in a cartographic file having the vector data structure, special nodes are separately generated at the boundary between the units (referred to as neighboring nodes hereinafter). The connection of a road can be traced between the neighboring units via the neighboring nodes. To specify the correspondence between a neighboring node of a unit and a neighboring node of a neighboring unit, the conventional cartographic files contain their offset addresses and record numbers. The offset address shows the address location of the neighboring node on the basis of a reference address. The record number shows where the neighboring node is recorded, counted from the first node in the cartographic file of the neighboring unit.
(Second Background Art)
As has been explained in First Background Art, the earlier conventional navigation systems could only use the cartographic files recorded in read-only recording media, so that it was difficult to provide them with real-time information. Typical examples of such real-time information include the traffic and weather information. A map providing system which can provide such real-time information and the cartographic files is disclosed in “Japanese Patent Laid-Open Publication No.7-262493”, for example. In the map providing system of this reference, the cartographic files and real-time information are downloaded from an information providing center to a terminal device carried on a car through a communication medium.
The map providing system is constructed on the basis of the mobile communication technology and digital broadcast technology to provide information in real time. In such a map providing system, the center station distributes information to a moving body in the service area by using a given broadcast channel. The center station is typically a communication satellite (so-called CS), a broadcasting satellite (so-called BS), or a ground wave digital broadcast station. A map providing system using the mobile communication technology and digital broadcast technology is disclosed in “Japanese Patent Laid-Open Publication No.7-154350”, for example. More specifically, this reference discloses technical contents for limiting the broadcast area for certain information. That is to say, when a center station sends multiplexed information through a broadcast medium, it attaches an area code, like a postal code, to each e of information. A terminal device previously records, in a memory, as an ID, the area code corresponding to its present position. In the terminal device, a data extracting circuit separates the multiplexed information sent from the broadcast station and extracts the area code attached to each piece of the information. The extracted area codes are compared with the recorded ID in the terminal device. When the two agree, the terminal device allows the user to refer to the information having the object area code.
As can be seen from the description above, map providing systems which provide maps through communication or broadcast are being intensively developed in these years. In such a map providing system, a center station reads out target cartographic files by the unit and sends them to a terminal device. The terminal device receives the cartographic data from the center station and stores it in the storage device. The stored cartographic file is used as needed, for user's reference, route search process, or map matching process.
(Problems of the First Background Art)
In the conventional systems, as is clear from the description in First Background Art, a cartographic file of a unit contains information which directly specifies the internal data structure of cartographic files in the neighboring units (the aforementioned offset addresses or record numbers).
For example, when a new road has been constructed in a unit, the cartographic file of this unit is updated, as a matter of course. In the updated cartographic file, the positions of the neighboring nodes have often been changed. Then, in the conventional method using information directly specifying the internal data structure of the cartographic files, it is impossible to correctly trace from a neighboring node recorded in a cartographic file of a neighboring unit to the corresponding neighboring node in the updated cartographic file. That is to say, updating one cartographic file often requires updating the cartographic files of its neighboring units.
Measures for evaluating the quality of the aforementioned digital cartographic files include the degree to which they give the details of the map. However, since the links are represented by vector data in the cartographic files, representing a more detailed map increases the amount of data of the cartographic file
Fukuda Hisaya
Ihara Yasuhiro
Nakano Nobuyuki
Suzuki Akihiro
Ueyama Yoshiki
Cuchlinski Jr. William A.
Donnelly Arthur D.
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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