JP2009204819A - Road map display system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To save resources for storing road map data without degrading the display quality of a road map in a road map display system. <P>SOLUTION: In the road map data of the road map display system, nodes N11-N14 made to correspond to a plurality of different links L1-L4 respectively are the nodes representing the same coordinate. In this system, for example, the coordinate values of nodes N12-N14 are deleted (Fig.5(a)) leaving only the coordinate value of the node N11 to save the resources for storage. Whereas, when the road map data is used, the coordinate value of the node N12 is restored from the coordinate value of the node N11 as shown in Figs.5(c) and (d), and sequentially, the coordinate value of the node N13 is restored from the coordinate vale of the node N12, and the coordinate value of the node N14 is restored from the coordinate vale of the node N13. Thus, the road map data before the coordinate values are deleted can be restored, and the quality of the road map data and, eventually, the display quality of the road map can be maintained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a road map display system that displays a road map represented by road map data.

  Conventionally, a road map display system that displays a road map represented by road map data is known. For example, in a navigation system for a vehicle, a road map represented by road map data is displayed on a display device such as a liquid crystal display, route information to a destination, and current position information of a vehicle acquired by GPS (Global Positioning System). The information is superimposed on the displayed road map and route guidance is given to the driver of the vehicle.

  The road map data used in this type of road map display system includes data indicating road connection status (road network data), data indicating road types, map matching data for improving position detection accuracy, and the like. (For example, see Patent Documents 1 and 2).

For example, as described in Patent Documents 1 and 2, the road network data includes information on nodes representing nodes or end points of the road network and information on links that are road sections connecting the nodes.
JP-A-8-69247 JP-A-8-68648

By the way, as described above, road map data includes various data, and the amount of data becomes a problem.
Furthermore, in the road network, when the configuration is represented in a form in which a plurality of roads are connected to a node, such as a cross intersection or a T-shaped intersection (that is, a plurality of links are connected to the same node). In this case, as described in Patent Documents 1 and 2, the information of the same node is assigned to the information of the plurality of links. That is, the same node information is duplicated in the road map data. Therefore, the problem of an increase in data amount has become more prominent.

  When the data amount of the road map data increases, for example, in the road map display system, more resources for storing the road map data are required, and the configuration and cost increase. Although it is conceivable to delete predetermined data having a low priority from the road map data, the quality of the road map data and, consequently, the display quality of the road map is deteriorated.

  The present invention has been made in view of these problems, and in a road map display system that displays a road map represented by road map data, a resource for storing road map data without reducing the display quality of the road map is provided. The goal is to be able to save.

  The road map display system according to claim 1, which has been made to achieve the above object, is acquired by a storage unit that stores information, a road map data acquisition unit that acquires road map data, and a road map data acquisition unit. Storage control means for storing the road map data in the storage means, display means for displaying information, road map data stored in the storage means is read from the storage means, and a road map represented by the read road map data is obtained. Display control means for displaying on the display means.

  The road map data includes at least node information indicating a node or an end point of a road network and link information indicating a road section between nodes, and each link information includes node information on a link end. . The nodal point corresponds to, for example, an intersection, and the end point corresponds to, for example, a dead end point.

  The road map data acquisition means has an erasure rule that when a plurality of link information in the road map data has the same node information, the node information other than one of the duplicated node information is erased. The applied road map data is acquired.

  On the other hand, when the display control means displays the road map represented by the road map data on the display device based on the road map data read from the storage means, the node information that has been deleted by applying the deletion rule is converted into one node information. Based on the restoration.

  In such a road map display system according to claim 1, the road map data acquired by the road map data acquisition means is road map data in which the node information other than one of the node information overlapping in the road map data is deleted. Therefore, it is possible to save resources for storing road map data. Therefore, the configuration and cost of the road map display system can be suppressed.

  On the other hand, the deleted node information is the same node information as the deletion target and is restored based on the one node information that is not the deletion target. Therefore, the quality of the road map data, and consequently the display quality of the road map Will not drop. That is, since the road map data of the conventional configuration in which each piece of link information has node information is restored, the road network is displayed reliably and appropriately. By the way, in the road map display system, normal road map data (road map data in which node information has not been deleted) is acquired by road map data acquisition means, and road map data in which the amount of data is reduced by applying an erasure rule is obtained. You may make it produce | generate.

Next, the road map display system according to claim 1 may be configured as in claim 2.
The road map display system according to claim 2 is the road map display system according to claim 1, wherein the road map data to which the erasure rule is applied is a storage location of node information to be erased (hereinafter referred to as a data erasure address). , Having data (hereinafter referred to as associated data) that is associated with a storage location (hereinafter referred to as a data non-erased address) of the one node information that is the same node information as that to be erased and that is not an object to be erased, The display control means restores the node information to be stored in the data erasure address based on the node information of the data non-erased address associated with the data erasure address by the associated data.

According to this, the erased node information can be reliably and easily restored. For this reason, the effect of Claim 1 can be acquired more reliably.
Next, the road map display system according to claim 3 is the road map display system according to claims 1 and 2, wherein in the road map data, the link information is stored in a predetermined storage order, and the erasure rule includes a plurality of link information. Among the same node information that are mutually included, the rules are such that all but the node information of the link information with the first storage order is deleted.

  In other words, among the same node information that a plurality of link information has, the node information that the first link information in the storage order has is left. According to such a simple configuration, for example, in the process of creating road map data with reduced data volume by applying an erasure rule (or in an apparatus for creating road map data with reduced data volume) This makes it easy to recognize the node information that becomes or the node information that is not to be erased. For example, it is possible to reduce the processing load in an apparatus that creates road map data with a reduced amount of data.

Next, in the road map display system of Claims 1-3, it is good to comprise like Claim 4.
The road map display system according to claim 4 is the road map display system according to claims 1 to 3, wherein in the road map data, for each node information, flag information indicating whether or not the node information can be deleted matches the deletion rule. The road map data provided by the road map data acquisition means is road map data from which node information that can be deleted according to flag information is deleted. .

  According to this, in the process of creating road map data with a reduced amount of data (or in an apparatus for creating road map data with a reduced amount of data), the node information can be easily deleted simply by referring to the flag information. It becomes possible to judge whether or not to do. For example, in an apparatus that creates road map data with a reduced amount of data, the processing load can be reduced. Moreover, since it is only necessary to delete the node information according to the flag information, the data amount of the road map data can be reduced more reliably. For this reason, the effect of Claim 1 can be acquired more reliably.

  Next, a road map display system according to a fifth aspect is the road map display system according to the first to fourth aspects, wherein the node information is information representing the coordinates of the nodal point (hereinafter referred to as coordinate information). It is said. That is, when the coordinate information of the nodal point is stored redundantly, the other coordinate information is erased while leaving one coordinate information out of the coordinate information. According to this, the data amount of road map data can be suppressed.

Embodiments of the present invention will be described below with reference to the drawings.
[First Embodiment]
FIG. 1 is a configuration diagram of a navigation system 1 according to a first embodiment to which a road map display system of the present invention is applied.

  In FIG. 1, a navigation system 1 includes a position detector 10, a media drive 11, a map data input device 12, an operation switch group 13, a remote control sensor 14, a remote control terminal (hereinafter referred to as a remote control) 14a, An external memory 15, a display unit 16, a voice recognition unit 17, a speaker 18, a transceiver 19, and a navigation ECU (ECU: electronic control unit) 20 that is connected to and controls each of these devices. I have.

  The navigation ECU 20 is configured as a normal computer, and includes a CPU, a ROM, a RAM, an I / O, and a bus line (all not shown) for connecting these configurations.

  The navigation ECU 20 performs predetermined processing (based on various information input from the position detector 10, the map data input device 12, the operation switch group 13, the remote control sensor 14, the external memory 15, the voice recognition unit 17, the transceiver 19, and the like. For example, map scale change processing, menu display selection processing, destination setting processing, route search execution processing, route guidance start processing, current position correction processing, display screen change processing, volume adjustment processing, and the like are executed.

  The position detector 10 is a known geomagnetic sensor 10a, gyroscope 10b, distance sensor 10c, and GPS receiver 10d for GPS (Global Positioning System) that detects the current position of the vehicle based on radio waves from the satellite. have. Since these sensors have errors of different properties, they are configured to be used while being complemented by a plurality of sensors. Depending on the accuracy, a part of the above may be used, and further, a steering rotation sensor, a vehicle sensor for each rolling wheel, or the like may be used.

  The media drive 11 is loaded with a storage medium (not shown), and updates road map data stored in the storage medium, so-called map matching data for improving the accuracy of position detection, various data including landmark data, and the like. Data can be read from the storage medium into the navigation system 1. As a storage medium, a CD-ROM or a DVD-ROM is generally used because of the amount of data, but a memory card, HDD, or the like may be used.

  The map data input device 12 stores road map data, map matching data, various data including landmark data read from the storage medium via the media drive 11 described above, and inputs these data to the navigation ECU 20. Device. An HDD, flash memory, or the like may be used as a data storage medium. The map data input device 12 may store data that should not be erased even after the power is turned off, or may store customized data or music data input in accordance with a user instruction.

  For example, a touch switch or a mechanical switch integrated with the display unit 16 is used as the operation switch group 13, and various functions (for example, map scale change, menu display selection, destination setting, route, etc.) are provided to the navigation ECU 20 by switch operation. Search, route guidance start, current position correction, display screen change, volume adjustment, etc.) are executed.

  The remote control 14a is provided with a plurality of operation switches (not shown), and various command signals are input to the navigation ECU 20 via the remote control sensor 14 by the switch operation. This causes the navigation ECU 20 to execute various functions as described above. The operation switch group 13 and the remote controller 14a can cause the navigation ECU 20 to execute the same function by any switch operation.

  By the way, when a desired destination is set via the remote controller 14a or via the operation switch group 13, the navigation ECU 20 selects an optimum route from the current position detected by the position detector 10 to the destination. Automatically search and set and display guidance routes. As a method for automatically setting an optimal route, a method such as the Dijkstra method is known.

  The set route is displayed on the display unit 16 based on information (road map data) from the map data input device 12. More specifically, a map (road map) based on the road map data is displayed on the display unit 16, and a current position mark indicating the current position detected by the position detector 10 is displayed on the displayed map. The route to the destination is superimposed and displayed. Information such as the current time and traffic jam information can also be displayed on the display unit 16.

The display unit 16 is capable of full-color display and can be configured using a liquid crystal display, an organic EL display, or the like.
The voice recognition unit 17 collates, for example, an operator's input voice input through a microphone (not shown) and lexical data (comparison target pattern) in a recognition dictionary (not shown) stored therein, and the degree of matching is the highest. Is input to the navigation ECU 20 as a recognition result. Based on the information (recognition result) from the voice recognition unit 17, the navigation ECU 20 performs predetermined processing (for example, map scale change processing, menu display selection processing, destination setting processing, route search execution processing, route search processing) Guidance start processing, current position correction processing, display screen change processing, volume adjustment processing, etc.).

The speaker 18 notifies the vehicle compartment of, for example, voice for route guidance, explanation of screen operation, or voice recognition result under the control of the navigation ECU 20.
The transceiver 19 receives traffic information, weather information, facility information, advertisement information, etc. provided from the outside (for example, an infrastructure such as a VICS system or a server such as the Internet), and transmits vehicle information, user information, etc. to the outside. It is a device to do. Information received from the outside is input to the navigation ECU 20. If necessary, the information processed by the navigation ECU 20 can be output to the outside via the transceiver 19.

Next, FIG. 2 is a diagram illustrating a configuration example of road map data.
In the present embodiment, for example, the road map data acquired via the media drive 11 has a link table as shown in FIG.

  The link table is a table that represents the connection relationship between roads, and is a collection of road (link) information. Specifically, the link table has link characteristic information in association with a link ID which is a link identification number. Examples of the link characteristic information include node information at both ends of the road (link), road type, road length, road width, and the like. Node information includes a node ID, which is a node identification number, and node coordinate information. In this embodiment, a coordinate omission flag indicating whether or not the coordinate information of the node can be omitted is assigned to each node information.

  Next, FIG. 3 is a flowchart showing a road map data generation process executed in the navigation ECU 20. This process is started when road map data having a link table as shown in FIG. 2 is read via the media drive 11, for example. The road map data generated by the processing of FIG. 3 is input to the map data input device 12 and stored in the map data input device 12. Further, the road map data stored in the map data input device 12 is input from the map data input device 12 to the navigation ECU 20 and used as necessary, such as when performing route guidance.

  In the road map data generation process of FIG. 3, first, in S110, a node included in the link table in the read road map data is searched (for example, a node ID is searched). More specifically, the nodes associated with the link IDs are searched in ascending order of the link IDs (in the order in which the link IDs are stored).

Next, the process proceeds to S120, and with reference to the coordinate omission flag assigned to the node searched in S110, it is determined whether or not the coordinate information of the node can be omitted (erased).
If it is determined in S120 that omission (erasure) is possible (S120: YES), the process proceeds to S130, and the coordinate information determined to be omissible (erasure) is erased. Then, the process returns to S110 to search for the next node.

If it is determined in S120 that omission (erasure) is impossible (S120: NO), the process returns to S110 to search for the next node.
Note that the processing of S110 to S130 is repeatedly executed for all the nodes. Then, when the process is executed for all the nodes, the process is terminated.

Further, the navigation ECU 20 inputs the road map data generated in the road map data generation process of FIG. 3 to the map data input device 12 and stores it in a separate process.
Next, FIG. 4 is a flowchart showing a road map data restoration process executed in the navigation ECU 20. Specifically, this is a process of restoring the omitted (erased) coordinate information for the road map data in which the coordinate information is omitted (erased) in the process of FIG. 3, and the coordinate information is omitted from the map data input device 12. Triggered when the (erased) road map data is input.

  In the restoration process of FIG. 4, first, in S210, a node included in the link table in the road map data is searched. More specifically, a node (node ID) associated with the link ID is searched in ascending order of the link ID.

  Next, the process proceeds to S220, and it is determined whether or not coordinate information (coordinate value) is assigned to the searched node (whether or not the node has coordinate information). Hereinafter, a node from which coordinate information (coordinate values) has not been deleted is referred to as a main node, and a node from which coordinate information (coordinate values) has been deleted is referred to as a sub-node.

  If it is determined in S220 that coordinate information (coordinate value) is assigned (S220: YES), the process proceeds to S230, and the coordinate information (coordinate value) and the same node (same coordinate as the main node that can be searched) The node IDs of the sub-nodes whose coordinate information (coordinate values) is omitted are stored as a pair in another memory (not shown). This point will also be described with reference to FIG. Then, the process returns to S210 again to search for the next node.

  On the other hand, if it is determined in S220 that the coordinate information (coordinate value) is not assigned (S220: NO), the process proceeds to S240, and the coordinate information (coordinate value) is not assigned with reference to the above-mentioned another memory. The coordinate information (coordinate value) stored as a pair with the node ID of the sub node is acquired. As a result, the coordinate information (coordinate value) that the subnode should have is restored for the subnode to which coordinate information (coordinate value) has not been assigned. Hereinafter, this secondary node is particularly referred to as a first secondary node.

  In S240, the restored coordinate information (coordinate value) and the same node as the first subnode in which the coordinate information (coordinate value) is restored, the coordinate information (coordinate value) is omitted. The node IDs of the other secondary nodes are stored in a separate memory (not shown) as a pair. Then, the process returns to S210 again to search for the next node.

Next, FIG. 5 is a drawing showing the operation of the present embodiment.
First, as a premise, FIG. 5B shows road map data (road map data before data amount reduction) of a conventional form. This road map data has links L1 to L4 and nodes N11 to N14, and represents a cross intersection. Specifically, the nodes N11 to N14 represent the same intersection. That is, the nodes N11 to N14 are nodes (same nodes) having the same coordinate information. In such a form of road map data, link L1 and node N11 are associated, link L2 and node N12 are associated, link L3 and node N13 are associated, and link L4 and node N14 are associated. . For example, the coordinate information (coordinate value) of the node N11 is assigned to the link L1, the coordinate information (coordinate value) of the node N12 is assigned to the link L2, and the coordinate information of the node N13 is assigned to the link L3. (Coordinate value) is assigned, and the coordinate information (coordinate value) of the node N14 is assigned to the link L4. That is, the coordinate information (coordinate values) of the nodes N11 to N14 is stored in the road map data. In other words, the same coordinate value (X1, Y1) is stored redundantly.

  Here, the road map data generated in the present embodiment is as shown in FIG. The road map data in the form of FIG. 5A is generated from the road map data in the form of FIG. 5B and is input (stored) in the map data input unit 12.

  Specifically, in the present embodiment, nodes N11 to N14 are searched in the road map data (S110), and based on the coordinate omission flag associated with each of the nodes N11 to N14 (S120), the node Among N11 to N14, the coordinate information (coordinate values) of the nodes N12 to N14 is deleted (S130). The purpose is to delete duplicate data. In this example, among the nodes N11 to N14 having the same coordinate information (coordinate values), the coordinate information (coordinate values) held by the node with the younger node ID (the storage order is the head) is left and the others are deleted. It is supposed to be. Specifically, the coordinate omission flag assigned to the node N11 represents “cannot be erased”, and the coordinate omission flag assigned to the nodes N12 to N14 is configured to represent “erasure is possible”.

  Therefore, as shown in FIG. 5A, (X1, Y1) representing coordinate information (coordinate values) is assigned only to the node N11. The nodes N12 to N14 do not have coordinate information (coordinate values).

  Next, FIGS. 5C and 5D show a form in which the road map data shown in FIG. 5B is restored from the road map data shown in FIG. As described above, when the road map data in the form of FIG. 5A is input from the map data input device 12 to the navigation ECU 20, the navigation map shown in FIG. The road map data is restored.

  First, a node is searched in the input road map data (S210). Specifically, nodes associated with the link ID are searched in ascending order of the link ID. In the example of FIGS. 5C and 5D, the nodes associated with the links L1 to L4 are searched in the order of the link L1, the link L2, the link L3, and the link L4. According to this, recognition is performed in the order of node N11 → node N12 → node N13 → node N14.

  As shown in FIG. 5D, information indicating the same node as itself (corresponding to the node ID given to the arrow and the arrow in FIG. 5D) is assigned to the nodes N11 to N14. . Specifically, for example, the node N11 is the same as the node N12, and information indicating that it is the same as the node N12 (information indicating the node N12) is associated with the node N11. Similarly, for example, the node N12 is the same as the node N13, and information indicating that it is the same as the node N13 (information indicating the node N13) is associated with the node N12. The same applies to the nodes N13 and N14. Such information is provided separately in the road map data.

  As a result of the node search (S210), it is determined that the first node N11 recognized in the link table has coordinate information (coordinate values) (S220: YES), as shown in FIG. 5C. The coordinate information (coordinate values), specifically, the value of (X1, Y1) is stored in another memory. At this time, the node ID of the node N12 indicated by the node N11 (associated with the node N11), that is, N12 is also stored in a separate memory in a pair. That is, N12 / (X1, Y1) is stored in a separate memory as a pair ((A)).

  Subsequently, as for the node N12 to be recognized next in the link table by the node search (S220), the coordinate information (coordinate value) is deleted for the node N12 as described above. In this case, another memory is referred to, and coordinate information (coordinate values) stored as a pair with the node ID N12 is acquired (S240). That is, the value of (X1, Y1) is acquired. Thereby, the coordinate information (coordinate value) of the node N12 is restored to (X1, Y1) in the link table. At this time, the coordinate information (coordinate value) of the node N12 and the node ID of the node N13 pointed to by the node N12 (associated with the node N12), that is, N13, are stored in a separate memory as a pair. That is, N13 / (X1, Y1) is stored in a separate memory as a pair ((B)). In other words, this means that N12 is rewritten to N13 in N12 / (X1, Y1) stored earlier.

Hereinafter, the description is omitted because the contents are the same, but the coordinate information (coordinate values) of the nodes N13 and N14 in the link table is similarly restored.
As described above, in the navigation system 1 of the present embodiment, overlapping coordinate information (coordinate values) is deleted from the road map data stored. For this reason, the data amount of road map data can be reduced. For this reason, in the navigation system 1, it is possible to save resources for storing road map data.

  On the other hand, in the navigation system 1, when using road map data from which overlapping coordinate information (coordinate values) is deleted (when read), the deleted coordinate information (coordinate values) is restored. For this reason, the quality of the road map data, and hence the display quality of the road map can be maintained. Moreover, as long as the road map data from which the overlapping coordinate information (coordinate values) has been deleted can be restored to the road map data before the coordinate information (coordinate values) has been deleted, the road map data (the road after the restoration) There is no need to change the application for using the map data. That is, for example, an existing application can be used.

In this embodiment, the map data input device 12 corresponds to storage means, the media drive 11 corresponds to road map data acquisition means, the navigation ECU 20 corresponds to storage control means and display control means, and the display unit 16 This corresponds to display means, and the information in another memory in FIG. 5C corresponds to the associated data.
[Second Embodiment]
Next, the navigation system 1 of 2nd Embodiment is demonstrated.

  The navigation system 1 of the second embodiment is different from the navigation system 1 of the first embodiment in that no coordinate omission flag is provided in the link table. Further, the difference is that the navigation ECU 20 executes the road map data generation process of FIG. 6 instead of the road map data generation process of FIG.

  Specifically, in the process of FIG. 6, first, in S310, a node (node ID) included in the link table is searched in the link table of the read road map data. More specifically, the nodes associated with the link IDs are searched in ascending order of the link IDs (in the order in which the link IDs are stored).

  Next, the process proceeds to S320, and it is determined whether or not the storage order of the searched node is the first among a plurality of nodes having the same coordinate information (coordinate value) as the node including the searched node. To do.

  If it is determined in S320 that it is not the head (S320: NO), the process proceeds to S330, and the coordinate information (coordinate value) assigned to the node is deleted. Then, the process returns to S310 to search for the next node.

  On the other hand, if it is determined in S320 that it is the head (S320: YES), the process returns to S310 to search for the next node. That is, the coordinate information (coordinate value) is not erased and remains for the node whose storage order is the head.

  In the navigation system 1 of the second embodiment as described above, road map data (see FIG. 5A) with a reduced data amount can be generated as in the first embodiment, which is the same as in the first embodiment. An effect can be obtained.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various form can be taken within the technical scope of this invention.
For example, in the above embodiment, among the same coordinate information (coordinate values), the first one in the storage order is left and the others are deleted. However, which one is left may be changed as appropriate. .

In the processing of S110 and S310 of the above embodiment, the nodes are searched in the storage order, but the search order is not limited.
In the above embodiment, instead of acquiring the road map data via the media drive 11, the road map data may be acquired through communication with the outside via the transceiver 19.

  Moreover, in the said embodiment, the structure by which the road map data by which the data amount was suppressed by deleting the overlapping node information is produced | generated outside (for example, another apparatus) and provided to the navigation system 1 may be sufficient. Specifically, the processes in FIGS. 3 and 6 may be executed in an external device.

It is a schematic structure figure of navigation system 1 of this embodiment. It is drawing showing the structure of the link table which road map data has. It is a flowchart showing the road map data generation process performed in navigation ECU20 (1st Embodiment). 4 is a flowchart showing a restoration process executed in navigation ECU 20. It is drawing showing the effect of this embodiment. It is a flowchart showing the road map data generation process performed in navigation ECU20 (2nd Embodiment).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Navigation system, 10 ... Position detector, 10a ... Geomagnetic sensor, 10b ... Gyroscope, 10c ... Distance sensor, 10d ... GPS receiver, 11 ... Media drive, 12 ... Map data input device, 13 ... Operation switch group, DESCRIPTION OF SYMBOLS 14 ... Remote control sensor, 14a ... Remote control, 15 ... External memory, 16 ... Display part, 17 ... Voice recognition unit, 18 ... Speaker, 19 ... Transceiver, 20 ... Navigation ECU.

Claims (5)

Storage means for storing information;
Road map data acquisition means for acquiring road map data;
Storage control means for storing the road map data acquired by the road map data acquisition means in the storage means;
Display means for displaying information;
Display control means for reading the road map data stored in the storage means from the storage means and displaying the road map represented by the read road map data on the display means;
In a road map display system equipped with
The road map data includes at least node information indicating a node or an end point of a road network and link information indicating a road section between nodes, and each link information includes node information on a link end. And
The road map data acquisition means applies an erasure rule that when a plurality of link information in the road map data has the same node information, all but one node information of the duplicate node information is erased Obtained road map data,
The display control means, when displaying the road map represented by the road map data on the display device based on the road map data read from the storage means, the node information that has been erased by applying the erase rule A road map display system characterized by being restored based on node information. In the road map display system according to claim 1,
The road map data to which the erasure rule is applied includes the storage location of node information to be erased (hereinafter referred to as a data erasure address), the same node information as the erasure target, and the one node that is not the erasure target It has data (hereinafter referred to as associated data) that associates the information storage location (hereinafter referred to as data unerased address),
The display control means restores the node information to be stored at the data erasure address based on the node information of the data non-erased address associated with the data erasure address by the associated data. Road map display system. In the road map display system according to claim 1 or 2,
In the road map data, the link information is stored in a predetermined storage order,
The erasure rule is a rule for erasing information other than the node information of the first link information in the storage order among the same node information that a plurality of link information has mutually. The road map display system according to any one of claims 1 to 3,
In the road map data, for each node information, flag information indicating whether or not the node information can be deleted is provided so as to match the deletion rule,
The road map data acquired by the road map data acquisition means is road map data from which node information that can be deleted according to the flag information is deleted. The road map display system according to any one of claims 1 to 4,
The road map display system, wherein the node information is information representing coordinates of the nodal point.

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