JP2007085768A - Navigation device and map data delivery system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a navigation device capable of reading out map data to be most efficiently, when partial data in the map data stored in a large capacity storage device are read out into a small capacity memory and used. <P>SOLUTION: A map data input device 7 in the navigation device 1 is allowed to store a map database 12A wherein a mesh which is the smallest reading-out unit of the map data is arrayed along the latitude and longitude directions, and a map database 12B wherein mesh is arrayed along each direction inclined at 45 degrees with respect to the directions. When reading out map data along a guide route from the map data input device 7 into a corridor memory 13, a control circuit 11 determines from which of the map databases 12A, 12B the map data are to be read out in order to reduce the total capacity of the map data, and selects the map database 12 as a reading-out source following the determination result. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides a navigation device that reads out and uses a part of map data stored in a mass storage device in order to perform navigation on a guide route to a destination, and map data used by the navigation device The present invention relates to a distribution system.

For example, in a navigation device for a vehicle, map data is often stored in a large-capacity storage device such as a DVD (Digital Versatile Disk) or a hard disk. Further, in recent navigation devices, in parallel with the navigation processing, for example, a so-called corrid (in order to respond to the need to play a DVD on which a movie or the like is recorded and to display the playback image on a display for viewing. Some have a Corridor function.
Here, the corridor function is to read only the map data along the guide route necessary for navigation from the storage device in advance to the memory (corrid memory), and thereafter read the map data from the corridor memory. Navigation function. Therefore, the DVD drive of the navigation device can play back DVDs other than map data. Even when map data is stored in the hard disk, the image or sound of the DVD being reproduced is not interrupted, and viewing can be performed comfortably.

In general, the capacity of the above storage device is on the order of gigabytes, whereas the capacity of the corridor memory is about several tens of megabytes. Therefore, how efficiently the necessary data is stored in the limited capacity memory. The issue is how to read. For example, Patent Document 1 discloses a technique in which only a block of map data related to a guide route is cut out from a map memory corresponding to the storage device and read out to a route memory corresponding to the corridor memory.
How to cut out the map data will be described with reference to FIGS. 13 and 14. FIG. 13 is a diagram showing a route set by the user and a map. 14 shows the map data minimum unit (unit of size for cutting out map data) superimposed on the map shown in FIG. 13 above, and the map data region cut out along the route (indicated by diagonal lines). ).
Japanese Patent No. 2663003

However, in the technique disclosed in Patent Document 1, when one guide route is set, the amount of data read to the route memory is defined by the number of blocks of map data including the route. It is not assumed that the amount of data will be reduced.
For example, as shown in FIG. 15, when the route from the current location to the destination G is relatively long, the minimum unit of the map data is a mesh, and the data capacity of one mesh is n. The capacity S of the corridor memory is assumed to be 15n. In the case of FIG. 15, when map data is cut out along the guide route, 19 meshes are obtained, so the total capacity L1 is L1 = 19n (> S). Therefore, in this case, it becomes impossible to read out all map data along the guide route.

  Moreover, the data capacity of 1 mesh differs according to the content of map data. For example, when there are many roads and facilities on the map and the data density is high as in the city center, the data capacity m of 1 mesh is equivalent to 2n. Then, as shown in FIG. 16, even if the guide route is short and 11 meshes, the total capacity L2 is L2 = 11m = 22n (> S).

  In order to deal with such a case, it is conceivable to reduce the amount of information of the map data on average. For example, data relating to the shape of the road remains, and names such as roads and intersections are not cut out. However, since it is normal to rely on names such as roads and intersections for intersections that determine the destination, the driver may not be able to select the traveling direction at the intersection with peace of mind. Alternatively, the map data may be cut out only in the area near the starting point and / or the destination according to the capacity. In this case, it is needless to say that the route guidance is incomplete.

Also, in general, in the navigation device, for example, when the user changes his / her destination or waypoint in the middle of his / her will, or he / she makes a mistake and deviates from the guide route, the guide route is searched again. It has a function. However, if the amount of map data read to the corridor memory along the initial guidance route is within the limit as a result of keeping it as small as possible, there may be cases where re-searching cannot be performed due to lack of surrounding data. .
Also, the map data used for navigation is preferably updated to the latest data as much as possible because roads may be newly constructed or changed by road construction or facilities may be removed or replaced. In view of this, a system has also been provided in which map data can be updated as needed by distributing it to each navigation device by communication. Even in this case, in order to suppress the communication fee required for distribution as much as possible and reduce the capacity of the storage device on the navigation apparatus side, it is desirable to reduce the capacity of map data to be distributed as much as possible.

The present invention has been made in view of the above circumstances, and an object of the present invention is to use a small-capacity memory when a part of map data stored in a large-capacity storage device is read and used. It is an object of the present invention to provide a navigation device capable of reading out map data so that it can be used as efficiently as possible with a limited capacity.
Another object of the present invention is to further reduce the capacity of map data to be distributed in a system for distributing map data used by a navigation device.

  According to the navigation device of the first aspect, the plurality of map databases having different storage forms of the map data are stored in the large-capacity storage device. Then, the reading control unit selects and reads any one map database that has good reading efficiency when reading the map data along the guide route from the large-capacity storage device to the small-capacity memory. That is, conventionally, since the problem of how to read out a part of map data has been dealt with on the assumption that there is only one map database, there is a limit to the efficiency of the reading. On the other hand, according to the present invention, the read control unit selects and reads out a map database having an appropriate storage form from which the read efficiency is good from among a plurality of map databases, thereby limiting the small-capacity memory. Map data can be used as efficiently as possible.

According to the navigation device of claim 2, the map database in which the minimum reading unit of the map data is arranged along the reference direction in the mass storage device, and the minimum reading unit is a predetermined angle with respect to the reference direction. One or more map databases arranged along an inclined direction are stored. Then, when reading a part of the map data from the large-capacity storage device to the small-capacity memory, the read control unit determines whether the total capacity of the map data is read from which of the plurality of map databases, and the determination A map database as a reading source is selected according to the result.
That is, the read control unit appropriately selects a map in which a part of the road of the guide route is distributed over a longer distance on a map of one minimum read unit from a plurality of map databases, and all of them are guided. If the routes are integrated, the total amount of map data read into the small-capacity memory becomes smaller. Therefore, it is possible to surely reduce the volume of map data that needs to be read for route guidance.

  According to the navigation device of the third aspect, at least one of the map databases in which the arrangement direction of the minimum readout unit is inclined with respect to the reference direction among the plurality of map databases is set to the inclination angle of 45 degrees. . In general, many roads on the map extend along the arrangement direction of the minimum readout unit (for example, east-west direction, north-south direction). Assuming various roads extending in other directions, the reference direction Map data with an inclination angle of 45 degrees is considered to be the most neutral setting for them. Accordingly, if at least a map database with an inclination angle of 45 degrees is provided, even when the number of map databases stored in the large-capacity storage device is small, the capacity of map data read along the guidance route can be efficiently reduced. You can choose one.

  According to the navigation device of the fourth aspect, the large-capacity storage device stores a plurality of map databases having different capacities in the minimum read unit of the map data. Then, the reading control unit determines whether the total capacity of the map data to be read into the small-capacity memory is maximized within a range that can be accommodated in the capacity of the small-capacity memory when reading from any of the map databases. To select a map database as a reading source. Therefore, the amount of map data along the guide route can be maximized within the limited capacity range of the small-capacity memory, and the small-capacity memory can be used efficiently.

  According to the navigation device of the fifth aspect, the reading control unit divides the guide route into a plurality of sections and performs selection for each section. That is, the direction in which the road as the guide route extends varies in various ways until the destination is reached. Therefore, if one guide route is divided into short distance sections and the map database to be selected for each section is determined, the reading can be performed more efficiently.

  According to the map data distribution system of claim 6, the data distribution host includes a map database in which the minimum reading unit of the map data is arranged along the reference direction, and the minimum reading unit is a predetermined angle with respect to the reference direction. If you have one or more map databases arranged along a tilted direction and you want to download a part of the map data to the navigation device, the total capacity of the map data is one of the multiple map databases. It is determined whether it becomes smaller when read out from, and a map database as a download source is selected according to the determination result. Therefore, since the data capacity when the map data is distributed to the navigation device can be reduced by the same action as in claim 2, the data distribution cost can be reduced and the data distribution time can be shortened. In addition, the capacity of the storage device on the navigation device side can be further reduced.

  According to the map data distribution system of claim 7, at least one of the map databases in which the arrangement direction of the minimum reading unit is inclined with respect to the reference direction among the plurality of map databases is set to 45 degrees. To do. Therefore, by the same operation as that of the third aspect, it is possible to select one that can efficiently reduce the capacity of map data to be read and distributed along the guide route.

  According to the map data distribution system of the eighth aspect, the data distribution host divides the guide route into a plurality of sections and performs selection for each section. Therefore, map data to be distributed by the same operation as in the fifth aspect. Can be efficiently reduced.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a vehicle navigation apparatus. The navigation device 1 includes a position detector (position acquisition means) 2 for detecting the current position of the vehicle, an operation switch 3, a remote control terminal (hereinafter referred to as a remote control) 4a, a remote control sensor 4 for inputting a signal from the remote control 4a, A communication device (communication means) 5, a VICS transceiver 6, a map data input device (mass storage device) 7, a display device 8, a voice input / output device 9, and an external memory 10 for storing various data are provided. . In addition, various processes are executed in accordance with information and data input via these, and a control circuit (reading control unit) 11 for controlling them is provided.

  The position detector 2 receives a radio wave transmitted from an artificial satellite for GPS (Global Positioning System) via a GPS antenna, and is added to the vehicle and a GPS receiver 2a that detects the position, direction, speed, etc. of the vehicle. A gyroscope 2b for detecting the magnitude of the rotational motion, a distance sensor 2c for detecting the distance traveled from the longitudinal acceleration of the vehicle, and the like, and a geomagnetic sensor 2d for detecting the traveling direction from the geomagnetism. Yes. Each of the sensors 2a to 2d has an error of a different property, and is configured to be used while complementing each other. Depending on the accuracy, some of the above-described sensors may be used, and other steering rotation sensors, wheel sensors of the respective rolling wheels, or the like may be used.

  As the operation switch 3 for inputting various instructions from the user, a touch panel installed on the display screen, a mechanical key switch provided around the display device 8 and the like are used. It is done. Note that the touch panel and the display device 8 are laminated and integrated, and there are various types of touch panels such as a pressure-sensitive method, an electromagnetic induction method, a capacitance method, and a combination thereof. May be. The remote controller 4a is an operation terminal for inputting various instructions in the same manner as the operation switch 3.

  The communication device 5 is connected to a car phone (not shown) and has a function of connecting to the Internet and acquiring information from a server on the network. The VICS transceiver 6 receives an FM broadcast signal via a radio antenna (not shown), or from a fixed station for a VICS (Vehicle Information and Communication System: registered trademark) service arranged near the road. A radio beacon signal and an optical beacon signal are received. This received information is sent to the control circuit 11 for processing.

The map data input device 7 is a device for inputting various data including so-called map matching data, map data, and mark data for improving the accuracy of position specification. As a recording medium for these data, a CD-ROM or DVD is generally used because of the amount of data, but another medium such as a magnetic storage device such as a hard disk or a memory card may be used.
The road data in the map data is a map constructed by connecting a plurality of nodes such as intersections with links. For each link, a unique number (link ID) for identifying the link and the length of the link are set. Link length, x and y coordinates of link start and end, link road width, road type (indicating road information such as toll road), road ID for identifying road (eg national highway ○ Link information consisting of data on such roads). In the map data, place name information, traffic information, and facility information are stored together with their coordinates (x, y coordinates).

  The map data input device 7 of the present embodiment stores two pieces of map data that have the same map contents but different storage forms. The map database 12A is a map that is generally used. As shown in FIG. 2A, a mesh, which is a minimum unit for reading map data, is arranged along a latitude line and a longitude line (reference direction). Has been. On the other hand, in the map database 12B, the meshes are arranged in a direction inclined 45 degrees with respect to the latitude line and the longitude line. The control circuit 11 selects and reads a part of the map data from these two map databases 12A and 12B, as will be described later. As an example, the mesh is a 2 km square area, and the data capacity of one mesh is about several hundred kilobytes. Further, since the storage capacity of the map data input device 7 is relatively large, there is room for allowing redundancy to store a plurality of map data having the same contents.

  The display device 8 for performing various displays such as a map display screen and a TV screen is a color display device such as a liquid crystal display, a plasma display, or a CRT, and any of them may be used. The display screen of the display device 8 includes a mark indicating the current location identified from the current position of the vehicle detected by the position detector 2 and the map data input from the map data input device 7, a guidance route to the destination, and a name. Additional data such as landmarks and various facility marks can be displayed in an overlapping manner. Also, a facility guide or the like can be displayed based on the facility information described above. The voice input / output device 9 recognizes the voice of the driver or the like input via a microphone (not shown), and also provides facility guidance and various guidance voices input from the map data input device 7, and communication devices 5 and 5. It is possible to output a read-out sound of information acquired through the VICS transceiver 6.

  The control circuit 11 is configured around a well-known microcomputer including a CPU, ROM, RAM, I / O and a bus line connecting these configurations. Based on a program stored in the ROM and RAM, Based on each detection signal from the position detector 2, the current position of the vehicle is calculated as a set of coordinates and traveling directions, or a map near the current position read via the map data input device 7 is displayed on the display device 8. Perform map display processing.

The control circuit 11 selects a destination facility according to the operation of the operation switch 3 or the remote controller 4a based on the point data stored in the map data input device 7, and the optimum route from the current position to the destination. Is automatically calculated, and route guidance processing is performed during driving of the vehicle. As a method for automatically setting an optimum route in this way, a method such as the Dijkstra method is known.
The control circuit 11 includes a corridor memory 13 which is an area allocated as a part of the RAM. When the guide route is calculated as described above, first, map data along the guide route is obtained as a map data input device. 7 and thereafter has a corridor function for performing route guidance based on map data stored in the corridor memory (small capacity memory) 13. The capacity of the corridor memory 13 is, for example, about several tens of megabytes.

  Next, the operation of this embodiment will be described with reference to FIGS. FIG. 3 is a flowchart showing the processing contents centered on the corridor function performed by the control circuit 11. Note that it is assumed that, before the execution of the flowchart of FIG. First, the control circuit 11 determines whether or not there is a request to execute the corridor function according to the user's setting input (step S1). If there is no request to execute the corridor function ("NO"), the map is a normal map. A setting is made such that route guidance is performed while reading out necessary map data from the database 12A at any time (step S9).

  On the other hand, when the user sets an execution request for the corridor function (step S1, “YES”), the control circuit 11 cuts out the map data along the searched guide route from the map database 12A (step S2), and then the map. Data is also cut out from the map database 12B (step S3). Then, it is determined which map database 12 is more efficient when the map database 12 is cut out (step S4).

  If one of the map databases 12A and 12B is adopted as a result of the comparison determination in step S4 (step S5 or S6), the control circuit 11 loads the map data cut out from the adopted map database 12 into the corridor memory 13. (Step S7). Thereafter, the map data input device 7 is not accessed until the route guidance is completed, and the route guidance is set while reading the map data from the corridor memory 13 (step S8).

Here, the details of the comparison process in step S4 will be described with reference to FIG. It is assumed that the capacities of the map data cut out from the map databases 12A and 12B in steps S2 and S3 are LA and LB, respectively. First, the control circuit 11 determines whether or not the map data capacities LA and LB both exceed the capacity S of the corridor memory 13 (step S11). If either one of the capacities LA and LB is equal to or smaller than the capacity S (“NO”), the capacities LA and LB are compared (Step S12), and the map database 12 having the smaller capacity is selected (Step S12). S13). If the free space of the corridor memory 13 has a margin at this time, the surplus area is released so that other applications can use it (step S14).
On the other hand, if both the capacities LA and LB exceed the capacities S in step S11 (“YES”), the map data reduction processing of the guide route is performed in the map databases 12A and 12B so as to be within the capacities S. Each is performed (step S15). The reduction processing here is performed in the same manner as that described with reference to FIGS. Then, the map database 12 with the smaller data reduction amount is selected (step S16).

  Next, a specific example of comparing the sizes of the capacitors LA and LB in step S12 will be described with reference to FIGS. FIGS. 5A and 5B show a case where the same guidance route is cut out from each of the map databases 12A and 12B. In this case, if the map database 12A shown in (a) is cut out, it becomes 15 mesh, and if it is cut out in the map database 12B shown in (b), it becomes 20 mesh. . That is, in the case of FIG. 5, since the guide route is composed of roads extending in the direction along the latitude and longitude, the above results are obtained.

  FIG. 6 shows patterns with different guide routes. In this case, if the map database 12A shown in FIG. 6A is cut out to 18 mesh, and the map database 12B shown in FIG. The capacity is smaller when the map data is cut out from 12B. That is, in the case of FIG. 6, since the guide route is composed of a road extending in a direction inclined by 45 degrees with respect to latitude and longitude, the above results are obtained.

  As described above, according to the present embodiment, the map data input unit 7 has the map database 12A in which the meshes, which are the minimum readout unit of the map data, are arranged along the latitude and longitude directions, and the meshes with respect to the above directions. The map database 12B arranged along the direction inclined 45 degrees is stored, and the control circuit 11 reads out the map data along the guide route from the map data input device 7 to the corridor memory 13. It is determined which of the map databases 12A and 12B the total capacity is read out, and the map database 12 as a reading source is selected according to the determination result. Therefore, it is possible to more effectively suppress the volume of map data that needs to be read for route guidance than before.

  And about the map database 12B, the mesh is arranged along the direction which inclined 45 degree | times with respect to the latitude and longitude directions. That is, in general, many roads on the map extend along the mesh arrangement direction along the latitude and longitude directions, and assuming various roads extending in other directions, the inclination relative to the above direction is assumed. Map data with an angle of 45 degrees is considered to be the most neutral setting for them. Therefore, even if there are two map databases 12 stored in the map data input device 7, it is possible to select one that can efficiently reduce the volume of map data read along the guide route.

(Second embodiment)
7 and 8 show a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted. Only different parts will be described below. The configuration of the second embodiment is basically the same as that of the first embodiment, and the contents of software processing by the control circuit 11 are different. FIG. 7 is a diagram corresponding to FIG. 3, and the control circuit 11 divides the guide route into a plurality of sections after executing Step S1 (Step S17). In steps S18 and S19 instead of steps S2 and S3, one of the divided sections is cut out from the map databases 12A and 12B. In the case of the second embodiment, in the comparison process shown in FIG. 4 of the first embodiment, the processes of steps S12 and S13 are performed only for one section.

  When the map database 12 having a smaller capacity is employed as a result of comparison determination for one section (steps S5 and S6), it is determined whether comparison determination has been performed for all sections (step S20). If all the sections have not been compared ("NO"), the process returns to step S18, and the remaining sections are compared. On the other hand, when the comparison determination is completed for all the sections (“YES”), the determination in step S11 shown in FIG. 4 is performed. If “NO”, the process proceeds to step S7 and the map data is loaded into the corridor memory 13. On the other hand, if “YES”, the process proceeds to step S7 after performing the process of step S15.

Here, FIG. 8 shows an example of the execution result of the flowchart of FIG. In FIG. 8, the guide route is divided into two sections, the map database 12B is selected for the first half section (1), and the map database 12A is selected for the second half section (2). That is, the direction in which the road of the guide route extends variously until reaching the destination. Therefore, when the guide route is divided into a plurality of sections and the capacity is compared for each section, a map suitable for each section is obtained. The database 12 can be selected.
As described above, according to the second embodiment, the control circuit 11 divides the guide route into two sections and performs the comparison determination in step S4 for each section. Therefore, the control circuit 11 selects a mesh for each section. If the power map database 12 is determined, the map data read capacity can be further reduced.

(Third embodiment)
9 and 10 show a third embodiment of the present invention. In the third embodiment, a map database 12C is stored instead of the map database 12B stored in the map data input device 7. As shown in FIG. 10, the mesh of the map database 12A is set to 2 km square, whereas the mesh of the map database 12C is set to 4 km square. That is, they are set so that the capacities of one mesh are different (map data storage forms are different).

  In the third embodiment, the processing contents shown in FIG. 4 in the first embodiment are different. That is, in step S21 instead of step S11, the control circuit 11 determines whether the capacities LA and LC of the map data cut out from the map databases 12A and 12C both exceed the capacity S of the corridor memory 13, respectively. If “YES” is determined, steps S15 and S16 are executed as in the first embodiment.

  If “NO” is determined in the step S21, it is subsequently determined whether any one of the capacitors LA and LC exceeds the capacity S (step S22). The smaller map database 12 is selected (step S23). If “NO” is determined in step S22, the sizes of the capacities LA and LC are compared (step S24), and the map database 12 having the larger capacity is selected (step S25). If there is still room in the capacity S of the corridor memory 13, step S14 is executed as in the first embodiment.

  As described above, according to the third embodiment, the map data input unit 7 stores the two map databases 12A and 12C having different map data capacities, and the control circuit 11 reads the map data to the corridor memory 13. Is read out from either of the map databases 12A and 12C, it is determined whether the maximum is within the range that can be accommodated in the capacity S of the corridor memory 13, and the map database 12 as a reading source is selected according to the determination result. Therefore, the amount of map data along the guide route can be maximized within the limited capacity range of the corridor memory 13, and the corridor memory 13 can be used efficiently.

(Fourth embodiment)
11 and 12 show a fourth embodiment of the present invention, and FIG. 11 shows the configuration of a map data distribution system. The map data distribution system includes a navigation device 21 and a map data distribution center (data distribution host) 22. When the navigation device 21 receives distribution of map data from the map data distribution center 22 as necessary, and writes the map data into a map data storage device 23 such as a hard disk drive (HDD), the map is stored from the storage device 23. It is configured to read out data and perform route calculation and route guidance. The control circuit 24 instead of the control circuit 11 does not include the corridor memory 13 unlike the above embodiments.

On the other hand, the map data distribution center 22 includes a storage device 25 in which the two map databases 12A and 12B provided in the map data input device 7 of the navigation device 1 in the first embodiment are stored. The map data distribution center 22 also includes a communication device (communication means) 26 for performing wireless communication with the navigation device 21 and a car phone (communication device 5) via a telephone communication network (not shown).
Then, when there is a map data distribution request from the navigation device 21 side, the map data distribution center 22 stores the map databases 12A and 12B in the same manner as the processing performed by the control circuit 11 of the navigation device 1 in the first embodiment. The selection is made to determine whether the capacity of the map data to be distributed is small, and as a result, the map data read from the selected map database 12 is distributed to the navigation device 21. Then, the navigation device 21 receives (downloads) the distributed map data via the communication device 5 and stores it in the map data storage device 23.

FIGS. 12A and 12B show examples of distribution target map data stored in the map databases 12A and 12B, respectively. In these map data, a newly opened road is drawn with a slightly thick line, and there are facilities newly created along the road. And only the map data along the newly opened road shall be delivered to the navigation apparatus 21.
Also in this case, when comparing the total capacity of the map data to be extracted from the map databases 12A and 12B, the map database 12A is 11 mesh and the map database 12B is 16 mesh, so the map database 12A has a smaller total capacity than the map database 12A. The extracted map data is distributed.

  As described above, according to the fourth embodiment, the map data distribution center 22 stores the two map databases 12A and 12B similar to those of the first embodiment in the storage device 25, and a part of the map data is navigated. When downloading to the device 21, it is determined which of the two map databases 12A and 12B the total capacity of the map data is read out, and the map database 12 as the download source is selected according to the determination result. . Accordingly, since the data capacity when the map data is distributed to the navigation device 21 can be reduced as in the first embodiment, the data distribution cost can be reduced and the data distribution time can be shortened. In addition, the capacity of the storage device 23 on the navigation device 21 side can be further reduced.

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications are possible.
There may be three or more map databases, and the inclination angle with respect to the latitude and longitude as the reference direction is set to 22.5 degrees, 30 degrees, 60 degrees, 67.5 degrees, for example, other than 45 degrees. It may be the one that
In the second embodiment, the number of divisions may be “3” or more.
The first embodiment and the third embodiment, and the second embodiment and the third embodiment may be combined.
In the method of the third embodiment, for example, the mesh size is enlarged only for the area near the current location or the destination location without selecting the mesh size uniformly for the entire guide route, or the user's past travel From the record, the mesh of an area where the traveling frequency is relatively low or has never traveled may be intensively increased.

A method similar to that of the second embodiment may be applied to the fourth embodiment.
In addition to the first to third embodiments, for example, the following can be considered as a criterion for selecting a map database having a good reading efficiency from a plurality of map databases.
・ Select the guide route that is distributed in the area closer to the center in the map data area to be cut out.
-Select the one that contains more main highways connected to the guide route.
・ Select a facility that contains more major facilities along the route.
-Select the one that contains fewer areas including the sea and mountains.
・ Choose one that contains more densely populated areas.
If a map database is selected based on these criteria, it is possible to select a map that has good reading efficiency according to each criterion.

1 is a block diagram illustrating a configuration of a vehicle navigation device according to a first embodiment of the present invention. (A), (b) is a figure which shows the arrangement direction of the map data mesh memorize | stored in two map databases, respectively. The flowchart which shows the processing content centering on a corridor function performed by the control circuit of a navigation apparatus. The flowchart which shows the detail of the comparison process in step S4 of FIG. (A), (b) is a figure which shows the data capacity in the case of cutting out the same map data each memorize | stored in two map databases (the 1) Fig. 5 equivalent (2) FIG. 3 equivalent view showing a second embodiment of the present invention. The figure which shows the state which combined the map data read from two map databases about each area which divided | segmented the guidance route | root FIG. 4 equivalent view showing a third embodiment of the present invention. (A), (b) is a figure which shows the magnitude | size of the map data mesh memorize | stored in two map databases, respectively. The functional block diagram which is 4th Example of this invention and shows the structure of a map data delivery system Figure equivalent to FIG. The figure which shows the clipping method of the map data which shows a prior art (the 1) The figure which shows the clipping method of the map data which shows a prior art (the 2) The figure explaining the relationship between how to cut out map data and the capacity of map data (part 1) FIG. 15 equivalent diagram (part 2)

Explanation of symbols

  In the drawings, 1 is a vehicle navigation device, 5 is a communication device (communication means), 7 is a map data input device (mass storage device), 11 is a control circuit (reading control unit), and 12A, 12B, and 12C are map databases. , 13 is a corridor memory (small capacity memory), 21 is a vehicle navigation device, 22 is a map data distribution center (data distribution host), 23 is a map data storage device, and 26 is a communication device (communication means).

Claims (8)

A large-capacity storage device in which map data is recorded is provided, and a part of the map data stored in the large-capacity storage device is read and used in order to perform navigation on the guide route to the destination. In navigation devices,
The large-capacity storage device stores a plurality of map databases with different map data storage forms,
Of the map data stored in the large-capacity storage device, a small-capacity memory in which a part of the data is read and stored,
A read control unit that selects and reads any one map database that provides good read efficiency when the map data along the guide route is read from the large-capacity storage device to the small-capacity memory. A navigation device. In the mass storage device, a map database in which minimum read units of map data are arranged along a reference direction, and the minimum read units are arranged along a direction inclined by a predetermined angle with respect to the reference direction. One or more map databases being stored,
The read control unit determines from which of the plurality of map databases the total amount of map data read into the small-capacity memory is reduced, and selects a map database as a read source according to the determination result The navigation device according to claim 1.   At least one of the map databases in which the arrangement direction of the minimum readout units is inclined with respect to the reference direction among the plurality of map databases is configured such that the inclination angle is set to 45 degrees. Item 3. The navigation device according to Item 2. The large-capacity storage device stores a plurality of map databases each having a different minimum read unit capacity for map data,
The read control unit determines whether the total capacity of the map data to be read to the small capacity memory is maximized within a range that can be accommodated in the capacity of the small capacity memory by reading from any of the plurality of map databases. 4. The navigation apparatus according to claim 1, wherein a map database as a reading source is selected according to a determination result.   The navigation device according to claim 1, wherein the read control unit divides the guide route into a plurality of sections and performs the selection for each section. A part of the map data stored in the storage device includes a communication means for communicating with the outside and a storage device in which the map data is recorded. A navigation device that reads and uses the data of
In a map data distribution system configured with a data distribution host that causes the navigation device to download a part of the map data held by itself to the navigation device,
The data distribution host is
A map database in which minimum readout units of map data are arranged along a reference direction, and one or more maps in which the minimum readout units are arranged along a direction inclined by a predetermined angle with respect to the reference direction A database and
When downloading a part of the map data to the navigation device, it is determined from which of the plurality of map databases the total capacity of the map data is read out, and a map as a download source according to the determination result A map data distribution system characterized by selecting a database.   At least one of the map databases in which the arrangement direction of the minimum readout units is inclined with respect to the reference direction among the plurality of map databases is configured such that the inclination angle is set to 45 degrees. Item 7. The map data distribution system according to item 6. The map data distribution system according to claim 6 or 7, wherein the data distribution host divides the guide route into a plurality of sections and performs the selection for each section.

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