Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2002-03-12
2002-08-06
Camby, Richard M. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S213000, C701S209000
Reexamination Certificate
active
06430499
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to information terminals and cartographic information providing systems and, more specifically, an information terminal and a cartographic information providing system for carrying out map display, position detection, route search, and route guidance by using digital cartographic data.
2. Description of the Background Art
(First Conventional Art)
In recent years, vehicles with a navigation system mounted thereon have been prevalent. Such conventional navigation system includes a map storage device having a read-only large-capacity storage medium, such as CD-ROM and DVD-ROM. A terminal for achieving this navigation system is implemented by a terminal dedicated to the navigation system, a general-purpose information processing device such as a PDA (Personal Digital Assistant), or other devices. The storage medium previously stores cartographic data for presentation to users. The storage device reads the cartographic data stored in the storage medium as required. The read digital cartographic data is used for route search or correction of a current position (map matching). To carry out these processes, the cartographic data contains road network data including at least connection information indicating how nodes and links are connected to one another. Here, each node indicates an intersection located on a road network, and each link indicates a vector representing a road located between two intersections (nodes) . The nodes and the links are connected to one another, and information about how they are connected is included in the road network data. Based on the road network data including a collection of the nodes, the links, and the connection information, the road network is presented on a map.
The nodes, the links, and the connection information are enough for representing a minimum required road network, but not enough for displaying a map. For example, roads on mountain or seashore ranges are often curved between intersections. To display the curved shapes of the roads, the road network data further includes information for specifying the shapes of the links.
Furthermore, to classify the roads by types, such as national highways, local roads, the number of lines, and the presence or absence of central reserves, the road network data further includes attribute information indicating the types of roads, etc.
Some intersections are provided with names, and some are not. Furthermore, some intersections have a traffic signal and some do not. Therefore, the road network data further includes attribution information for each node. The attribution information for each node contains a name of the intersection corresponding to the relevant node, the presence or absence of a traffic signal, etc.
(Second Conventional Art)
As described in the above first conventional art, the conventional navigation system can use only the cartographic data recorded on the read-only storage medium, and therefore can hardly provide real-time information. Such real-time information is typified by, for example, traffic information and weather information. Japanese Patent Laid-Open Publication No. 7-262493 (1995-262493) discloses a map providing system capable of providing real-time information and cartographic data. In this map providing system, real-time information and cartographic data are downloaded from an information providing center (center station) through a communications medium to a vehicle-mounted terminal. Furthermore, to achieve the above navigation system, a terminal having a small data storage capacity, such as a general-purpose information processing device (PDA, cell phone terminal, etc.) , may be used for downloading the cartographic data from the center station.
The above map providing system is constructed based on mobile terminal communications technologies and digital broadcast technologies for providing various information on a real-time basis. In the above constructed map providing system, the center station distributes information to the mobile terminal located within a service area by using a predetermined broadcast channel. The center station is typified by a communications satellite (CS), a broadcast satellite (BS), or a ground-wave digital broadcast station. An example map providing system using these mobile terminal communications technologies and digital broadcast technologies is disclosed in Japanese Patent Laid-Open Publication No. 7-154350 (1995-154350), wherein a technique for limiting a broadcast area capable of receiving specific information is disclosed.
In the map providing system disclosed in Japanese Patent Laid-Open Publication No. 7-154350, a center station adds an area code, such as a postal code, to specific multiplexed information when transmitting it through a broadcast medium. A receiving terminal, on the other hand, registers in advance the area code corresponding to an area that covers its current position in memory as the ID. In the terminal, a data extracting circuit separates multiplex information distributed from the center station to extract the area code added to the information. The terminal then compares the extracted area code with the ID registered in advance in the memory. If they match, the terminal enables the user to refer to the information with the area code added thereto.
As such, map providing systems for providing a terminal with cartographic data through telecommunications or broadcasting have been increasingly developed in recent years. In such map providing systems, the center station transmits cartographic data to the terminal, and the terminal receives the cartographic data and then stores it in a storage device. The stored cartographic data is used as required by users for carrying out viewing, route search, map matching, or other processing.
As described in the above first conventional art, the road network is conventionally represented by nodes and links, and the connection information among the nodes and the links is recorded in advance in the cartographic data. This is to quickly and efficiently read the connection information of the road network data in the cartographic data. However, the connection information among the nodes and the links recorded in the cartographic data is so detailed that the cartographic data becomes extremely large in amount.
Here, processing such as route search and map matching by using the cartographic data is briefly described.
FIG. 11
is a schematic illustration showing example nodes and links represented by the cartographic data.
In
FIG. 11
, a road network represented in the cartographic data is composed of eight nodes N
1
to N
8
and twelve links L
1
to L
12
. To carry out route search and map matching by using the road network, how the nodes and the links are connected has to be traced. For example, when the shortest route starting from the node N
1
to the node N
8
is traced as the node N
1
->the link L
2
->the node N
3
->the link L
6
->, the node N
5
->the link L
9
->the node N
6
->the link L
11
->the node N
8
, the route has to be traced as in the following processes.
Process 1: The node N
1
has two links connected thereto, one of which is the link L
2
.
Process 2: The link L
2
is connected to the node N
3
.
Process 3: The node N
3
has five links connected thereto, one of which is the link L
6
.
Process 4: The link L
6
is connected to the node N
5
.
Process 5: The node N
5
has three links connected thereto, one of which is the link L
9
.
Process 6: The link L
9
is connected to the node N
6
.
Process 7: The node N
6
has four links connected thereto, one of which is the link L
11
.
Process 8: The link L
11
is connected to the node N
8
.
In other words, the connection information has to include node-to-link information indicating which link is connected to each node (Processes 1, 3, 5, and 7) , and link-to-node information indicating which node is connected to each link (Processes 2, 4, 6, and 8).
Described next is road network data for tracing the route by using such connect
Iwami Ryotaro
Kindo Tsuyoshi
Nakano Nobuyuki
Camby Richard M.
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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