Patent Publication Number: US-2009234572-A1

Title: Surrounding Search Data Generating System, Surrounding Search System, Surrounding Search Data Generating Method, Surrounding Search Method, and Navigation Apparatus

Description:
TECHNICAL FIELD 
     The present invention relates to a surrounding search data generating system, a surrounding search system, a surrounding search data generating method, a surrounding search method, and a navigation apparatus. 
     BACKGROUND ART 
     In conventional navigation apparatuses, a current location of a vehicle is detected with the use of, for example, a GPS (Global Positioning System) sensor, map data is read from a data recording unit, and a map screen is formed on a displaying unit, so that a vehicle position indicating the current location, a map of the surroundings of the vehicle location and the like are displayed on the map screen. Thus, the operator of such a navigation apparatus (i.e., the driver of the vehicle) is able to drive the vehicle in accordance with the vehicle location, the map of the surroundings of the vehicle location, and the like that are displayed on the map screen. 
     When the driver of the vehicle inputs a destination and specifies a search criterion, a route search process is performed based on the search criterion. Accordingly, a search is conducted for a route to drive from a starting point indicated as the current location to the destination, based on the map data. The route that has been found in the search, i.e., the “searched route”, is displayed on the map screen together with the vehicle location, so that guidance for the searched route, i.e., “route guidance”, is provided. Thus, the driver is able to drive the vehicle along the searched route that is displayed. 
     While the driver is driving a vehicle on a road, if he/she wishes to search for facilities (i.e., objects) that are located in the surroundings (vicinity) of the current location, the navigation apparatus conducts a search for facilities that are positioned within a predetermined area (e.g., an area having a radius of 30 kilometers) in which the current location is located at the center. Of the facilities that have been found in the search, the navigation apparatus displays, in a list as a search result, only the facilities that are located within a band-shaped area having a predetermined width and that is centered on the road (e.g., 100 meters to the left and to the right of the road) on which the vehicle is driven. In a case where the road on which the vehicle is driven is a limited access-road, such as an expressway or a toll road, for example, when the driver specifies an exit of the limited access road, the navigation apparatus conducts a search for facilities that are located in the vicinity of the specified exit. See, for example, Japanese Patent Application Publication No. 2004-170233 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, the conventional navigation apparatus conducts a search for only the facilities that are located in the vicinity of the specified exit. Thus, in a case where the driver of the vehicle wishes to find the most appropriate facility, for example, a facility that he/she is able to reach in a short period of time, the driver needs to specify a plurality of exits, one by one. In this situation, not only do the operations required of the driver become bothersome, but also the level of efficiency of the search is low. 
     It is an object of the present invention to solve the problems of the conventional navigation apparatuses and to provide a surrounding (vicinity) search data generating system, a surrounding (vicinity) search system, a surrounding (vicinity) search data generating method, a surrounding (vicinity) search method, and a navigation apparatus that make it possible to conduct a search for the most appropriate one facility while a vehicle is driven on a limited access road, e.g. expressway, to simplify the operations required of the driver, and to enhance the level of efficiency of the search. 
     Means for Solving the Problems 
     In order to achieve the object, a surrounding (vicinity) search data generating system according to the present invention includes: a facility judgment processing means for judging whether a predetermined facility is located within a surrounding (vicinity) search area that is specified (predefined) along a road having an entrance and an exit; a first data generation processing means for generating, in a case where the predetermined facility is located within the surrounding search area, data for the predetermined facility as first data; a target point setting processing means for setting, at a predetermined location, a target point to be used as a target for generating second data; a condition satisfaction judgment processing means for judging whether there is any facility that satisfies a predetermined data generation condition; a second data generation processing means for generating, in a case where there are one or more facilities that satisfy the predetermined data generation condition, data for the one or more facilities that satisfy the predetermined data generation condition as second data, in correspondence with the target point; and a data record processing means for recording the first data and the second data onto a recording medium. 
     EFFECTS OF THE INVENTION 
     According to the present invention, not only for the facilities that are positioned within the surrounding search area, but also for the facilities that satisfy the data generation condition, the second data is generated, so that the facilities are used as the targets of the surrounding (vicinity) search. Thus, it is possible to easily conduct a search for the facility most appropriate for the driver. Consequently, it is possible to not only simplify the operations of the operating unit required of the driver, but also enhance the level of efficiency of the search. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a navigation system according to a first embodiment of the present invention. 
         FIG. 2  illustrates a surrounding (vicinity) search according to the first embodiment of the present invention. 
         FIG. 3  is a block diagram of a data generating apparatus according to the first embodiment of the present invention. 
         FIG. 4  is a flowchart of a method for generating dummy data included in surrounding (vicinity) search data according to the first embodiment of the present invention. 
         FIG. 5A  is a functional block diagram of a surrounding search data generating system according to the first embodiment of the present invention; and  FIG. 5B  is a functional block diagram of a navigation apparatus according to the first embodiment of the present invention. 
         FIG. 6  is a flowchart of a routine executed by a surrounding (“vicinity”) search processing means according to the first embodiment of the present invention. 
         FIG. 7  shows an example of a category selecting screen according to the first embodiment of the present invention. 
         FIG. 8  shows an example of a search result display screen according to the first embodiment of the present invention. 
         FIG. 9  shows is a drawing that shows an example of a search result display screen according to a second embodiment of the present invention. 
     
    
    
     BRIEF EXPLANATION OF THE REFERENCE NUMERALS 
     
         
           14 : NAVIGATION APPARATUS 
           35 : DISPLAYING UNIT 
           51 : INFORMATION CENTER 
           63 : NETWORK 
         AR 1 : SURROUNDING SEARCH AREA 
         e 1 , e 2 : EXIT 
         Hw 1 , Hw 2 : AUTOMOBILE-ONLY ROAD 
         Jc: JUNCTION 
         Pr: CURRENT POSITION 
         p 1 -p 4 : TARGET POINT 
         r 1 -r 3 : GENERAL ROAD 
         Sa 1 -Sa 3 : SERVICE AREA 
       
    
     PREFERRED EMBODIMENTS OF THE INVENTION 
     Embodiments of the present invention will be explained in detail, with reference to the accompanying drawings. 
       FIG. 1  is a diagram that shows a navigation system according to a first embodiment of the present invention. 
     In the drawing,  14  denotes an information terminal such as, for example, an in-vehicle navigation apparatus that is installed in a vehicle.  63  denotes a network.  51  denotes an information center that serves as an information provider. An embodiment of a navigation system according to the present invention includes the navigation apparatus  14 , the network  63 , and the information center  51 . 
     The navigation apparatus  14  includes: a GPS sensor  15  that detects a current location of the vehicle by receiving a satellite signal generated by an artificial satellite; a data recording unit  16  that serves as an information recording unit and also as a storage device and that has recorded therein map data, i.e. information related to maps, as well as other various types of information such as information related to facilities; a navigation processing unit  17  that performs various types of computational processes such as a navigation process, based on various types of information; a direction sensor  18  that detects a direction in which the vehicle is oriented, i.e., heading of the vehicle; an operating unit  34  that serves as a first input unit and is used by a driver of the vehicle who is an operator of the navigation apparatus  14  for input; a displaying unit (display unit)  35  that serves as a first output unit and displays various types of images on a screen (not shown in the drawing) so as to inform the driver; an audio input unit  36  that serves as a second input unit and is used for audio input; an audio output unit  37  that serves as a second output unit that provides various types of audio information to the driver, and a communicating unit  38  that serves as a transmitting and receiving unit and functions as a communication terminal. The GPS sensor  15 , the data recording unit  16 , the direction sensor  18 , the operating unit  34 , the displaying unit  35 , the audio input unit  36 , the audio output unit  37 , and the communicating unit  38  are connected to the navigation processing unit  17 . 
     The GPS sensor  15  is configured so as to be able to detect the current location and also to detect a current time, the speed of the vehicle, and the like. 
     As shown in  FIG. 1 , according to the present embodiment, the GPS sensor  15  and the direction sensor  18  are separate elements. However, it is acceptable to have another arrangement in which a current location is detected based on a combination of position coordinates, a direction, and a traveling direction with the use of the GPS sensor  15  and the direction sensor  18  that together serve as a current position (current location) detecting unit. Alternatively, because the GPS sensor  15  is able to calculate the speed and the traveling direction of the vehicle based on the received satellite signals, it is acceptable to determine the current location using only the GPS sensor  15 . 
     Also, although the GPS sensor  15  is used in the present embodiment, it is acceptable to use, instead of the GPS sensor  15 , a distance sensor, a steering sensor, an altimeter, and the like, individually or in combination. Also, although the direction sensor  18  is used to detect the direction of the vehicle in the present embodiment, it is acceptable to use, instead of the direction sensor  18 , a gyro sensor, a geomagnetic sensor, or the like, in combination. 
     Further, connected to the navigation processing unit  17  are an accelerator sensor  42  that serves as an engine load detecting unit and that detects operation of the accelerator pedal (not shown in the drawing), based on degree of accelerator opening; a brake sensor  43  that serves as a braking detecting unit and detects operation of the brake pedal (not shown in the drawing), based on the amount by which the brake pedal is depressed; and a vehicle speed sensor  44  that serves as a vehicle speed detecting unit and detects vehicle speed S. An operation information detecting unit that detects the information related to the operations performed by the driver on the vehicle is constituted by elements including the accelerator sensor  42  and the brake sensor  43 . The GPS sensor  15  is able to detect the vehicle speed, in addition to the current location and the direction of the vehicle. 
     The data recording unit  16  has a map database that includes map data files. The map database stores therein map data. The map data includes intersection data related to intersections, node data related to nodes, road data related to roads and road links, search data that has been processed for the use in searches, facility data related to facilities, and surrounding search data (vicinity search data) that has been generated in order to conduct a search for facilities that are located in the vicinity of a route that has been specified in advance (predefined) or the current location of the vehicle, in other words, data in order to conduct a surrounding area search, as well as feature data related to features. The data recording unit  16  also has recorded therein data used for outputting predetermined information via the audio output unit  37 . 
     In addition, the data recording unit  16  has a statistic database that includes statistic data files and a driving history database that includes driving history data files. The statistic data files and the driving history data files respectively contain statistical data and driving history data, as actual record data. 
     The statistical data is history information that consists of the actual records, i.e., a history of traffic information that was provided in the past. The statistical data is generated from various types of information individually or in combination and, as necessary, applying a processing step and/or a statistical process thereto. Examples of the various types of information include: traffic information that was provided in the past by a road traffic information center (not shown in the drawing) such as a VICS (a registered trademark: Vehicle Information and Communication System) center or a RDS-TMC (Radio Data System-Traffic Message Channel: traffic information service using an FM multiplex broadcast) that serves as an information provider; road traffic census information that is data indicating amounts of traffic based on a road traffic census provided by the Japanese Ministry of Land, Infrastructure, and Transport; and road time table information provided by the Japanese Ministry of Land, Infrastructure, and Transport. 
     The data items in the statistical data include: link numbers corresponding to the road links; direction flags indicating directions in which vehicles are driven; information types indicating the types of information; the levels of traffic congestion corresponding to predetermined time periods; link required travel time indicating the time required to drive the road links during the predetermined time periods; and average data for the link required travel time corresponding to different days of the week (for example, data for weekday average). 
     The driving history data indicates actual driving records, i.e., the actual records of the driving of vehicles on the various roads as collected by the information center  51  from a plurality of vehicles such as the vehicle on which the navigation apparatus is installed and/or other vehicles. The driving history data is calculated and accumulated as probe data, based on the driving data. 
     The data items in the driving history data include: travel time that is required in order to drive the road links during predetermined time periods; and levels of traffic congestion experienced while driving the road links during the predetermined time periods. The statistical data may include the driving history data. Also, in the present embodiment, the levels of traffic congestion are used as a traffic congestion index indicating the degree of traffic congestion. The levels of traffic congestion include “congested”, “crowded”, and “not congested”. 
     The data recording unit  16  includes a disk (not shown in the drawing) such as a hard drive, a CD, a DVD, an optical disk, or the like, for the purpose of recording various types of data. The data recording unit  16  also includes a head, which is not shown in the drawing, such as a read/write head that is used for reading or writing various types of data. It is also possible to use a memory card or the like, as the data recording unit  16 . 
     In the present embodiment, the data recording unit  16  includes the map database, the statistic database, the driving history database, and the like. However, it is also acceptable to include the map database, the statistic database, the driving history database, and the like in the information center  51 . 
     The navigation processing unit  17  includes: a CPU  31  that serves as a controlling device that performs the overall control of the navigation apparatus  14  and also serves as a computing device; a RAM  32  that is used as a working memory while the CPU  31  executes various types of computational processes; a ROM  33  that has recorded therein a program used for the over control by CPU  31 , as well as other various types of programs for conducting a search for a route to a destination and for providing route guidance; and a flash memory (not shown in the drawing) that is used for recording therein various types of data and programs. 
     In the present embodiment, various types of programs are recorded in the ROM  33  and various types of data are recorded in the data recording unit  16 . However, alternatively, both the programs and the data may be recorded on a disk or the like. In this case, it is possible to read the programs, the data, and the like from the disk and to write the read programs and the read data into a flash memory. Thus, it is possible to update the programs, the data, and the like by replacing the disk. Further, it is possible to receive the programs, the data, and the like via the communicating unit  38  and to write the received programs and the received data into the flash memory included in the navigation processing unit  17 . 
     The operating unit  34  is operated by the driver and is used for correcting a current location that is indicated when starting the vehicle, inputting a starting point and/or a destination, inputting a location point to be driven through, and/or turning on the communicating unit  38 . As the operating unit  34 , it is acceptable to use a keyboard, a mouse, and the like that are provided independently of the displaying unit  35 . Alternatively, as the operating unit  34 , it is acceptable to use a touch panel that allows a user to perform predetermined input operations by touching or clicking operations performed on various types of keys, switches, and buttons that are displayed as images on a screen formed on the displaying unit  35 . 
     A display device may be used as the displaying unit  35 . On the various types of screens formed on the displaying unit  35 , it is possible to display the current location of the vehicle and to display a direction of the vehicle, to display maps, a searched route, i.e. a route determined by search, guidance information along the searched route, and traffic information, to display the distance to the next intersection on the searched route, and to display the direction to be taken at the next intersection. In addition, it is possible to display operation guidance, operation menus, and guidance related to the keys for the image operating unit, the operating unit  34 , the audio input unit  36 , and the like, as well as broadcast programs provided by FM multiplex broadcast. 
     The audio input unit  36  is a microphone or the like (not shown in the drawings), enabling input of necessary information by voice. The audio output unit  37  includes a voice synthesizer and a speaker, which are not shown in the drawing. From the audio output unit  37 , the searched route, the guidance information, the traffic information, and the like are output by using, for example, voice synthesized by the voice synthesizer. 
     The communicating unit  38  includes: a beacon receiver that receives, as a radio or optical beacon signal, various types of information including current traffic information transmitted from the road traffic information center and other general information, via a radio beacon or optical beacon provided roadside; and an FM receiver that receives various types of information as an FM multiplex broadcast from a FM broadcast station. The traffic information includes traffic congestion information, traffic regulation information, parking information, traffic accident information, and information regarding degree of congestion in service areas. The general information includes news, weather forecasts, and the like. The beacon receiver and the FM receiver are integrated into a unit as a VICS receiver; however, the beacon receiver and the FM receiver may be separate units. 
     The traffic information includes: information types indicating the types of information; grid numbers each identifying a grid unit; link numbers each identifying a road link that connects two points (for example, two intersections) and each indicating direction of travel on the road link (currently driven direction or direction of opposing lane or lanes); and link information that shows the content of the information provided in correspondence with the link numbers. For example, when the traffic information is traffic congestion information, the link information includes: congestion beginning-point data indicating a distance from a starting point on the road link to the beginning point of traffic congestion; the level of traffic congestion; a congestion length indicating the length of the congested section from the beginning point of the traffic congestion to the end of the traffic congestion, and link required travel time indicating the length of time required to drive the road link. 
     The communicating unit  38  functions to receive, from the information center  51 , various types of data such as the map data, the statistical data, and the driving history data, as well as various types of information such as the traffic information and the general information, via the network  63 . 
     In order to realize such functions, the information center  51  includes: a server  53 ; a communicating unit  57  that is connected to the server  53 ; and a database (DB)  58  that serves as an information recording unit. The server  53  includes a CPU  54  that serves as a controlling device and also serves as a computing device, a RAM  55 , and a ROM  56 . The database  58  has recorded therein various types of data that are the same as the data recorded in the data recording unit  16 , such as the map data, the statistical data, and the driving history data. Further, the information center  51  functions to provide, in a real-time manner, various types of information including the current traffic information that has been transmitted from the road traffic information center and general information, as well as driving history data that has been collected from a plurality of vehicles (such as the vehicle on which the navigation apparatus is installed and/or other vehicles). 
     The navigation system, the navigation processing unit  17 , the CPU  31 , the CPU  54 , and the server  53  function as a computer, individually or in combination of two or more, so as to perform computational processes based on the various types of programs and the various types of data. A recording medium in the form of a disk, a memory card, or the like that is inserted into the data recording unit  16 . Additional recording mediums include the RAM  32 , the RAM  55 , the ROM  33 , the ROM  56 , the database  58 , the flash memory, and the like. The computing device, may be a MPU or the like, instead of the CPU  31  or the CPU  54 . 
     Next, the basic operation of the navigation system described above will be explained. 
     First, when the driver operates the operating unit  34  to activate the navigation apparatus  14 , a navigation initialization processing means (i.e., a navigation initialization processing unit), that is included in the CPU  31 , executes a navigation initialization process, to read the current location of the vehicle that has been detected by the GPS sensor  15  and the direction of the vehicle that has been detected by the direction sensor  18  and also initializes the various types of data. Next, a matching processing means (i.e., a matching processing unit), that is included in the CPU  31 , executes a matching process so as to identify the current position by determining the road link on which the current position is located, based on a locus of the current position that has been read and on the shapes and the positional arrangements of the road links that constitute the roads surrounding the current location. 
     After that, an information obtainment processing means (i.e., an information obtainment processing unit), that is included in the CPU  31 , performs an information obtainment process, so as to obtain the map data by either reading it from the data recording unit  16  or by receiving it from the information center  51  or the like, via the communicating unit  38 . In a case where the information obtainment processing means obtains the map data from the information center  51  or the like, the information obtainment processing means downloads the received map data into a flash memory. 
     Subsequently, a display processing means (i.e., a display processing unit), that is included in the CPU  31 , displays one of the various types of screens on the displaying unit  35 . For example, a map display processing means (i.e., a map display processing unit), included in the display processing means, executes a map display routine so as to form a map screen on the displaying unit  35 , to display a map of the vicinity on the map screen, to display the current position as the vehicle location and to display vehicle direction. 
     Accordingly, the driver of the vehicle is able to drive the vehicle according to the map, the current location of the vehicle, and the direction of the vehicle. 
     When the driver operates the operating unit  34  to input a destination, a destination setting processing means (i.e., a destination setting processing unit), that is included in the CPU  31 , executes a destination setting routine to set a destination. The driver is also able to input and set a starting point, as necessary. Also, the driver is able to register a predetermined location in advance and to set the registered location as a destination. The driver then operates the operating unit  34  to input a search criterion, and a search criterion setting processing means (i.e., a search criterion setting processing unit), that is included in the CPU  31 , then executes a search criterion setting routine to set the search criterion. 
     When the destination and the search criterion have been set as explained above, a route search processing means (i.e., a route search processing unit), that is included in the CPU  31 , executes a route search routine in which it reads the current location, the destination, and the search criterion and also reads the search data and the like from the data recording unit  16 . The route search processing means conducts a search for a travel route from the starting point, indicated as the current location, to the destination, subject to the search criterion and based on the current location, the destination, the search data, and the like, and outputs route data indicating the route determined by search, i.e. the searched route. The route that has the smallest sum of link costs is selected as the searched route. 
     In a case where a road has a plurality of lanes, and the driving lane has also been detected, the route search processing means conducts the search for the travel route, i.e. “searched route”, in units of lanes. In this case, the route data includes a lane number for the driving lane. 
     Subsequently, a guidance processing means (i.e., a guidance processing unit), that is included in the CPU  31 , executes a guidance routine to provide route guidance. To execute that routine a route display processing means (i.e., a route display processing unit), included in the guidance processing means, executes a route display routine so as to read the route data and display the searched route on the map screen, according to the route data. In the case where the search is conducted for the searched route in units of lanes, the route display processing means provides route guidance with reference to lanes at a predetermined location, such as a guidance intersection, and displays the driving lane for which the route guidance is provided in an enlarged map of the intersection. In addition, as necessary, an audio output processing means (i.e., an audio output processing unit), that is included in the guidance processing means, generates an audio (voice) output to provide route guidance for the searched route via the audio output unit  37 . 
     Also, the information center  51  is able to perform a route search in which the CPU  31  transmits the current location, the destination, the search criterion, and the like to the information center  51 . When the information center  51  has received the current location, the destination, the search criterion, and the like, a route search processing means (i.e., a route search processing unit), that is included in the CPU  54 , executes a route search routine that is the same as the one performed by the CPU  31 , so as to read the search data and the like from the database  58 . The route search processing means conducts a search for a travel route from the starting point to the destination, under the search criterion, based on the current location, the destination, the search data, and the like and outputs route data for the searched route. Subsequently, a transmission processing means (i.e., a transmission processing unit), that is included in the CPU  54 , executes a data transmission routine to transmit the route data to the navigation apparatus  14 . Thus, in the navigation apparatus  14 , when a basic information obtainment processing means (i.e., a basic information obtainment processing unit), that is included in the CPU  31 , has received the route data from the information center  51 , the guidance processing means performs the route guidance as described above. 
     In a case where there is a guidance intersection on the searched route, when the vehicle has reached a route guidance point that is positioned a predetermined distance (e.g., X meters) in advance of the guidance intersection, an enlarged intersection map display processing means (i.e., an enlarged intersection map display processing unit), included in the guidance processing means, executes an enlarged intersection map display process to generate an enlarged intersection map as described above in a predetermined area of the map screen and to provide route guidance using the enlarged intersection map. More specifically, the enlarged intersection map display processing means displays, in the enlarged intersection map, a map of the vicinity of the guidance intersection, the searched route, and landmarks such as facilities that can be used as landmarks at the guidance intersection. In the case where the route guidance is provided relating to lanes, the enlarged intersection map display processing means also displays the driving lane. In addition, as necessary, the audio output processing means outputs audio instruction, for example, “Turn left after X meters”, from the audio output unit  37  the route guidance. 
     It is also possible to use the navigation apparatus  14  or the navigation system as a surrounding search system to conduct a search for a facility (i.e., an object) that is located in the surroundings of the current location, the destination, the searched route, and the like. When the driver operates the operating unit  34  or the audio input unit  36  to request, for example, a search to be conducted for a facility that is located in the surroundings of the searched route, the surrounding search data is read from the data recording unit  16 , the database  58 , or the like, so that a search is conducted for a facility located in the vicinity of the searched route, and the driver is informed of the facility found in the search. 
     Next, a method for generating the surrounding search data will be explained. 
       FIG. 2  illustrates a surrounding (vicinity) search according to the first embodiment of the present invention.  FIG. 3  is a block diagram of a data generating apparatus according to the first embodiment of the present invention.  FIG. 4  is a flowchart of method for generating dummy data included in the surrounding search data according to the first embodiment of the present invention. 
     In  FIG. 2 , Pr denotes the current location. Hwi (i=1, 2, . . . ) denotes a limited access road, e.g. an automobile-only road such as an expressway or a toll road that has one or more entrances and exits and that has limited access. rj (j=1, 2, . . . ) denotes a general road such as a national road or a prefectural road. In the present embodiment, the automobile-only road Hw 1  serves as a searched route Rt. 
     Lwα (α=1, 2, . . . ) denotes a rampway used as an entrance or exit. ltβ (β=1, 2, . . . ) denotes an interchange. eβ (β=1, 2, . . . ) denotes an exit with a gate provided at an interchange ltβ. Saγ (γ=1, 2, . . . ) denotes a service area that is provided as a “stop-over” area. In the example of the present embodiment, service areas (Saγ) are used as “stop-over” areas; however, parking areas may also be “stop-over” areas. Each of the service areas (Saγ) has a parking space, a service facility such as a restaurant, as well as a gas station. GSδ (δ=1, 2, . . . ) denotes a gas station that is provided in a service area (Saγ), on a general road rj, or the like. 
     At a service area Sa 1 , a service lane (“rampway”) Lw 1  branches off from the main lanes of the automobile-only road Hw 1  and merges back into the main lanes. A gas station GS 1  accessed by the service lane Lw 1 . A rampway Lw 2  is provided at an interchange It 1  so as to connect the limited access road Hw 1  and a general road r 2  together. An exit e 1  is provided on the rampway Lw 2 . A gas station GS 2  is provided on the general road r 2 , whereas a gas station GS 4  is located on general road r 1 . 
     The rampway Lw 3  connects the limited access road Hw 1  and the limited access road Hw 2  at a junction Jc. A rampway Lw 4  branches off from the rampway Lw 3  so as to connect the rampway Lw 3  and a general road r 3 . An exit e 2  is provided on the rampway Lw 4 . A gas station GS 3  is located on the general road r 3 . 
     At a service area Sa 2 , a service lane (“rampway”) Lw 5  branches off from the main lanes of the limited access road Hw 1  and merges back into the main line. A gas station GS 5  is provided on the service lane Lw 5 . At a service area Sa 3 , a service lane Lw 6  branches off from the main lanes of the limited access road Hw 1  and merges back into the main lanes. A gas station GS 6  is accessed by the service lane Lw 6 . 
     Next, the method for generating the surrounding search data will be explained, with reference to  FIGS. 3 and 4 . 
     A disk (not shown in the drawing) that is to be inserted into the data recording unit  16  ( FIG. 1 ) is produced by a disk provider who is an information generator. Thus, the disk provider generates and edits the surrounding search data and records the surrounding (vicinity) search data onto the disk, by using a data generating apparatus  61 . It is also possible to generate or edit the surrounding search data and to record the surrounding search data into a flash memory or the GPS sensor  15 , by using the navigation apparatus  14  or the server  53 . In this situation, various types of processes executed by a surrounding search data generating unit  64 , included in the data generating apparatus  61 , are performed by the navigation processing unit  17  or the server  53 . 
     The data generating apparatus  61  includes a driver  65  in addition to the surrounding search data generating unit  64 . The driver  65  drives a recording head or the like, which is not shown in the drawing, in order to record the surrounding search data generated by the surrounding search data generating unit  64  onto the disk. 
     The surrounding search data generating unit  64  includes a server  71  and a database (DB)  72 . The server  71  includes: a CPU  74  that serves as a computing device; a RAM  75  that is used as a working memory for the CPU  74  in its execution of various types of computational processes; and a ROM  76  that has recorded thereon various types of data, programs, and the like. The database  72  contains the same data as that recorded in the data recording unit  16  or the database  58 . A surrounding search data generation means (i.e., a surrounding search data generation processing unit  90 ), that is included in the CPU  74 , executes a surrounding search data generation routine so as to generate surrounding search data for certain roads such as limited access road Hw 1 , based on the map data that has been read from the database  72  and to record the generated surrounding search data onto the disk. The CPU  74  included in the data generating apparatus  61  functions as a computer. 
     When surrounding search data is generated for a limited access road Hwi, for example, for the limited access road Hw 1  shown in  FIG. 2 , a surrounding search area AR 1  is specified in advance along the limited access road Hw 1 , the surrounding search area AR 1  having a predetermined width La (e.g., 100 meters) to the left and to the right of the limited access road Hw 1 . Data for the facilities that are located within the surrounding search area AR 1  is recorded onto the disk as the surrounding search data, with classification by category. The surrounding search data includes the name of each of the facilities, coordinates indicating the position of each of the facilities, information about each of the facilities, a link number indicating a road link along which each of the facilities is located, and the like. 
     The distance La can be arbitrarily selected when the surrounding search data is generated. However, as the distance La is increased the surrounding search area AR 1  becomes larger and the number of facilities to be found in the search becomes larger, and it thereby becomes more difficult for the driver to find the most appropriate one facility. On the other hand, as La is decreased, because the surrounding search area AR 1  becomes smaller, the number of facilities to be found in the search becomes smaller, and it becomes more difficult to detect the most appropriate facility for the driver. 
     To cope with the above-described problem, in the present embodiment, the surrounding search data is generated and recorded onto the disk in such a manner that, even if La is set to be short, it is possible to conduct a search also for facilities that are located outside of the surrounding search area AR 1 , but satisfy a predetermined data generation condition. 
     In the present embodiment, the surrounding search data includes first data and second data. The first data is real data, which is data for the facilities that are actually located within the surrounding search area AR 1 . The second data is dummy data, which is data for facilities that is generated when the data generation condition is satisfied, no matter whether or not the facilities are actually located within the surrounding search area AR 1 . The dummy data is data that is expected to be useful for the driver, no matter whether the facilities are positioned within the surrounding search area AR 1  or not. The dummy data is set, generated, and recorded onto the disk, by using a format as if the facilities were located within the surrounding search area AR 1 . 
     Referring to  FIG. 5A , in the present embodiment, when the real data is to be generated, a facility judgment means (i.e., a facility judgment processing unit  91 ) that is included in the surrounding search data generation processing means  90 , executes a facility judgment routine to judge whether there is any facility in the surrounding search area AR 1  that is in the same category as a facility used as a target for which the surrounding search data is to be generated. In a case where there are one or more facilities in the surrounding search area AR 1  that are in the same category as the facility used as the target for which real data is to be generated, a real data generation means (i.e., a real data generation processing unit  92 ), that is included in the surrounding search data generation processing means  90  and that serves as a first data generation processing means, executes a first data generation process to generate data for the one or more facilities as the first data, which is the real data. After that, a data recording means (i.e., a data recording unit  93 ) that is included in the surrounding search data generation processing means  90 , executes a data record routine to record the real data onto the disk. The real data includes the name of each of the facilities, coordinates indicating the location of each of the facilities, information about each of the facilities, a link number indicating the road link on which each of the facilities is located, and the like. 
     When the dummy data is to be generated, first, a target point setting means (i.e., a target point setting processing unit  93 ) that is included in the surrounding search data generation processing means  90 , executes a target point setting process to set, as target points pε (ε=1, 2, . . . ), location points to be used as the targets for generating dummy data, at predetermined locations within the surrounding search area AR 1  such as, in the example of the present embodiment, in the vicinity of the branching points where roads branch off from a limited access road Hwi, such as, in the example of the present embodiment, in the vicinity of the branching points of the rampways Lwα. Exits of a limited access road Hwi may be set as the target points, as necessary. 
     Next, a condition satisfaction judgment means (i.e., a condition satisfaction judgment processing unit  94 ) that is included in the surrounding search data generation processing means  90 , executes a condition satisfaction judgment process to judge, with regard to the target facility for which the surrounding search data is to be generated, whether or not the data generation condition for generating dummy data is satisfied. To execute the judgment process, the condition satisfaction judgment means follows the road while searching a predetermined area such as an area within a distance threshold value (e.g., 2 kilometers, in the example of the present embodiment) in terms of the linear distance from each of the target points pε and judges whether, in each of the areas around the target points PE, there is any facility that is in the same category as the target facility. The road is followed taking traffic regulations such as one-way streets into consideration. Alternatively, instead of following the road, a search may be conducted to determine a route from the target point pε to each of the facilities. Also, it is acceptable to change the distance threshold value, as necessary. 
     In a case where the data generation condition is satisfied and there are one or more facilities within the area that are in the same category as the target facility, a dummy data generation means (i.e., a dummy data generation processing unit  95 ) that is included in the surrounding search data generation processing means  90  and that serves as a second data generation means, executes a second data generation process, to generate data for those facilities in the same category, as the second data, which is the dummy data, in correspondence with each of the target points pε. The dummy data includes the location of each of the target points pε, the name of each of the facilities, coordinates indicating the location of each of the facilities, information about each of the facilities, the linear distance from the target point pε to each of the facilities, the route distance that is measured for travel along the road, and the like. 
     Subsequently, the data recording unit  96  executes a data recording process so as to record the dummy data onto the disk in correspondence with the target points pε. 
     For example, in  FIG. 2 , a target point p 1  is set on the rampways Lw 1  and Lw 2  that branch off from the limited access road Hw 1  to the service area Sa 1  and the exit e 1 , respectively. A target point p 2  is set on the rampways Lw 3  and Lw 4  for the junction Jc and the exit e 2 , respectively. A target point p 3  is set on the rampway Lw 5  to the service area Sa 2 . A target point p 4  is set on the rampway Lw 6  in correspondence with the service area Sa 3 . 
     Subsequently, for example, when surrounding search data is to be generated for a gas station GS 5  along the limited access road Hw 1 , because the gas station GS 1  is actually located within the surrounding search area AR 1  that is specified along the limited access road Hw 1 , the data for the gas station GS 1  will be recorded as real data. Also, because the gas station GS 1  is located within 2 kilometers from the target point p 1  in terms of the linear distance, the data for the gas station GS 1  will also be recorded as dummy data, in correspondence with the target point p 1 . 
     Because the gas station GS 2  is not located within the surrounding search area AR 1 , the data for the gas station GS 2  will not be recorded as real data; however, because the gas station GS 2  is located within 2 kilometers from the target point p 1  in terms of the linear distance, the data for the gas station GS 2  will be recorded as dummy data in correspondence with the target point p 1 . 
     Because the a gas station GS 3  is not located within the surrounding search area AR 1 , the data for the gas station GS 3  will not be recorded as real data; however, because the gas station GS 3  is located within 2 kilometers from the target point p 2  in terms of the linear distance, the data for the gas station GS 3  will be recorded as dummy data in correspondence with the target point p 2 . 
     The gas station GS 4  is located within the surrounding search area AR 1 , but is not located on the automobile-only road Hw 1 . In this situation, the data for the gas station GS 4  will be recorded as real data. In addition, because the gas station GS 4  is located within 2 kilometers from the target point p 2  in terms of the linear distance, the data for the gas station GS 4  will also be recorded as dummy data in correspondence with the target point p 2 . 
     Because the gas station GS 5  is actually located within the surrounding search area AR 1 , the data for the gas station GS 5  will be recorded as real data. In addition, because the gas station GS 5  is located within 2 kilometers from the target point p 3  in terms of the linear distance, the data for the gas station GS 5  will also be recorded as dummy data in correspondence with the target point p 3 . 
     Because the gas station GS 6  is not located within the surrounding search area AR 1 , the data for the gas station GS 6  will not be recorded as real data; however, because the gas station GS 6  is located within 2 kilometers from the target point p 4  in terms of the linear distance, the data for the gas station GS 6  will be recorded as dummy data in correspondence with the target point p 4 . 
     Next, the flowchart in  FIG. 4  will be explained. 
     Step S 1 : Set target points pδ. 
     Step S 2 : Follow the road from the target points pε. 
     Step S 3 : Judge whether there is any facility that is in the same category as a facility used as a target (“target facility”). In a case where there are one or more facilities that are in the same category as the target facility, the process proceeds to step S 4 . In a case where there is no facility that is in the same category, the process ends. 
     Step S 4 : Generate dummy data. 
     Step S 5 : Record the dummy data in correspondence with the target points pε, and end the process. 
     In the present embodiment, the navigation apparatus  14  executes the display routine so as to display a map on the map screen and also executes the route search routine. When a vicinity search is conducted for a general road or the like, only the real data is used. However, when a surrounding (vicinity) search is conducted for the limited access road Hw 1 , both the real data and the dummy data are used. 
     Next, operation of the surrounding search means in conducting a surrounding search for a gas station GSδ (one of the various categories of facilities), while the vehicle is driven along the searched route Rt, will be explained. In this embodiment, both the navigation apparatus  14  and the information center  51  are able to perform the surrounding search. In this J 0  embodiment, the surrounding search processing means included in the CPU  31  and that included in the CPU  54  perform the same operation. Thus, only the operation performed by the surrounding search processing means (i.e., a surrounding search processing unit  80 ) included in the CPU  31  of the navigation apparatus  14  will be explained, operation of the surrounding search means included in the CPU  54  of the information center  51  being the same. 
       FIG. 5B  is a functional block diagram of the navigation apparatus according to the first embodiment of the present invention.  FIG. 6  is a flowchart of operations performed by the surrounding search means according to the first embodiment of the present invention.  FIG. 7  shows an example of a category selecting screen according to the first embodiment of the present invention.  FIG. 8  shows an example of a search result display screen according to the first embodiment of the present invention. 
     When a driver operates the input operating unit  34  ( FIG. 1 ) or the audio input unit  36  so as to request that a surrounding search be conducted for the searched route Rt ( FIG. 2 ), a category display means (i.e., a category display processing unit  81 ), that is included in the surrounding search unit  80 , executes a category display routine so as to provide a category selecting screen as shown in  FIG. 7  and to display all the categories such as department stores, gas stations, golf courses and hospitals. When dummy data is included in the surrounding search data for any of the categories, (i.e., the “gas stations” category in the example of the present embodiment), a symbol D indicating that dummy data is included is appended to the category. 
     When the driver operates the input operating unit  34  or the audio input unit  36  to select one of the categories, for example, the category “gas stations”, a category judgment means (i.e., a category judgment processing unit  82 ), that is included in the surrounding search processing unit  80 , executes a category judgment process so as to judge whether or not a category including dummy data has been selected. In a case where a category including dummy data has been selected, in other words, when the category “gas stations” has been selected, a surrounding search data obtainment means (i.e., a surrounding search data obtainment processing unit  83 ) that is included in the surrounding search processing unit  80 , executes a surrounding search data obtainment routine so as to obtain the surrounding search data by reading it from the data recording unit  16 . 
     Next, a dummy data presence judgment means (i.e., a dummy data presence judgment processing unit  84 ), that is included in the surrounding search processing unit  80 , executes a dummy data presence judgment routine to judge whether or not the obtained surrounding search data includes dummy data. In a case where the obtained surrounding search data does include dummy data, a data judgment means (i.e., a data judgment processing unit  85 ), that is included in the surrounding search processing unit  80 , executes a data judgment routine to judge whether the dummy data matches the real data, based on the names and the coordinates of the gas stations. In a case where the dummy data matches the real data, the data judgment means judges whether there is any gas station located on the limited access road Hw 1 . In a case where one or more gas stations are located on the limited access road Hw 1 , in order to ensure that the dummy data and the real data will not be displayed in duplicate, a data change means (i.e., a data change processing unit  86 ), that is included in the surrounding search processing unit  80 , executes a data change process, an internal process using the dummy data as real data, so that the dummy data will be treated as real data in the surrounding search process. Conversely, in a case where no gas station is located on the limited access road Hw 1 , the data change means executes an internal process while using the dummy data as real data and giving priority to the dummy data, so that the dummy data will be treated as real data in the surrounding search process. 
     Subsequently, a distance calculation means (i.e., a distance calculation processing unit  87 ), that is included in the surrounding search processing unit  80 , executes a distance calculation routine to calculate the distance from the current location to each of the gas stations, i.e., a distance Li (i=1, 2, . . . ) between the current location and each facility, by referring to the surrounding search data. In execution of this routine, for the real data, the distance calculation means calculates the distance Li between the current location and each facility, based on a route distance measured from the current location to each of the gas stations along the road. For the dummy data, the distance calculation means calculates the distance Li between the current location and each facility by adding a first distance and a second distance together, the first distance being the distance of the route measured from the current location to a target point ps corresponding to a gas station, and the second distance being the linear distance from the target point pε to the gas station. Alternatively, for the dummy data, the distance calculation means may calculate the distance Li between the current location and each facility by adding a first distance and a second distance together, the first distance being the distance of the route measured from the current location to a target point pε corresponding to a gas station, and the second distance being the distance of the route measured from the target point pε to the gas station. 
     For example, the gas station GS 1  shown in  FIG. 2  is located within the surrounding search area AR 1 . Thus, both real data and dummy data are recorded as the surrounding search data. Utilizing the real data, a distance L 1  between the current position and the facility is calculated based on the lengths of the actual road links that are a part of the limited access road Hw 1  and the rampway Lw 1 . For the dummy data, the distance L 1  between the current location and the facility is calculated by adding a route distance and a linear distance together, the route distance being measured from the current location Pr to the target point p 1 , and the linear distance being measured from the target point p 1  to the gas station GS 1  and having been recorded in advance. 
     Because the gas station GS 2  is not located within the surrounding search area AR 1 , only dummy data is recorded as the surrounding search data. Accordingly, a distance L 2  between the current location and the facility is calculated by adding a route distance and a linear distance together, the route distance being measured from the current location Pr to the target point p 1 , and the linear distance being measured from the target point p 1  to the gas station GS 2 . 
     Because the gas station GS 3  is not located within the surrounding search area AR 1 , only dummy data is recorded as the surrounding search data. Accordingly, a distance L 3  between the current location and the facility is calculated by adding a route distance and a linear distance together, the route distance being measured from the current location Pr to the target point p 2 , and the linear distance being measured from the target point p 2  to the gas station GS 3 . 
     The gas station GS 4  is located within the surrounding search area AR 1 . Thus, both real data and dummy data are recorded as the surrounding search data. For the real data, a distance L 4  between the current location and the facility is calculated by adding the length of the road link and a linear distance together, the road link being a part of the limited access road Hw 1  up to a location point positioned close to the gas station GS 4 , and the linear distance being measured from the limited access road Hw 1  to the gas station GS 4 . For dummy data, a distance L 4  between the current location and the facility is calculated by adding a route distance and a linear distance together, the route distance being measured from the current location Pr to the target point p 1 , and the linear distance being measured from the target point p 1  to the gas station GS 4 . 
     The gas station GS 5  is positioned within the surrounding search area AR 1 . Thus, both real data and dummy data are recorded as the surrounding search data. To obtain the real data, a distance L 5  between the current location and the facility is calculated based on the length of the actual road link that is a part of the limited access road Hw 1  and the rampway Lw 5 . For the dummy data, a distance L 5  between the current location and the facility is calculated by adding a route distance and a linear distance together, the route distance being measured from the current location Pr to the target point p 3 , and the linear distance being measured from the target point p 3  to the gas station GS 5 . 
     Because the gas station GS 6  is not located within the surrounding search area AR 1 , only dummy data is recorded as the surrounding search data. Accordingly, a distance L 6  between the current location and the facility is calculated by adding a route distance and a linear distance together, the route distance being measured from the current location Pr to the target point p 4 , and the linear distance being measured from the target point p 4  to the gas station GS 6  and having been recorded as dummy data. 
     Subsequently, a search means (i.e., a search processing unit  88 ), that is included in the surrounding search processing unit  80 , executes a search process to search for gas stations by selecting dummy data and real data for the gas stations, in an ascending order of the distance Li between the current location and the facility, starting with the gas station having the shortest distance Li. A search result display means (i.e., a search result display processing unit  89 ), that is included in the surrounding search processing means  80 , executes a search result display routine to provide a search result display screen as shown in  FIG. 8  on the display unit  35  and to display the search results, i.e., a list of the gas stations that have been found in the search. The search result display means is included in a distance guidance output means (i.e., a distance guidance output processing unit). The distance guidance output means executes a distance guidance output routine to output distance guidance regarding the distance to the facilities to the display unit  35 . 
     For example, for the gas stations GS 1  and GS 5  shown in  FIG. 2 , both the dummy data and the real data are recorded as the surrounding search data. However, because the dummy data matches the real data, and also the gas stations GS 1  and GS 5  are located on the limited access road Hw 1 , the dummy data is treated as real data. The distance L 1  between the current location and the facility will be displayed as 2.5 kilometers, which is obtained by adding a route distance of 2 kilometers and a linear distance of 0.5 kilometers together. The distance L 5  between the current location and the facility will be displayed as 6.5 kilometers, which is obtained by adding together a route distance of 6 kilometers and a linear distance of 0.5 kilometers. For the gas stations GS 2 , GS 3 , and GS 6 , only the dummy data is recorded as the surrounding search data. The distance L 2  between the current location and the facility will be displayed by adding together a route distance of 2 kilometers and a linear distance of 1 kilometer. The distance L 3  between the current location and the facility will be displayed by adding together a route distance of 2.5 kilometers and a linear distance of 0.5 kilometers. The distance L 6  between the current location and the facility will be displayed by the method of adding together a route distance of 9 kilometers and a linear distance of 1 kilometer. Further, for the gas station GS 4 , both the dummy data and the real data are recorded as the surrounding search data. However, because the dummy data matches the real data, and also because the gas station GS 4  is not located on the limited access road Hw 1 , the dummy data is given priority. The distance L 4  between the current location and the facility will be displayed by adding together a route distance of 2 kilometers and a linear distance of 1.5 kilometers together. The symbols D are appended to indicate that the distances L 2 , L 3 , and L 6  between the current position and the facilities respectively correspond to the gas stations GS 2 , GS 3 , and GS 6  for which only dummy data has been recorded as the surrounding search data and that the distance L 4  between the current position and the facility corresponds to the gas station GS 4  for which the dummy data has been given priority. 
     On the other hand, in a case where the driver does not select a category that includes dummy data from the category selecting screen and, instead selects, for example, the category “department stores”, the surrounding search data obtainment means obtains the surrounding search data. The distance calculation processing means then calculates a distance Li between the current location and the facility based on a route distance measured from the current location to each of the department stores, by referring to the surrounding search data. 
     Subsequently, the search means conducts a search for department stores by selecting only the real data for the department stores, in an ascending order of distance between the current location and the facility, starting with a department store having the shortest distance. The search result display means then displays, in a list, the department stores that have been found in the search. 
     Similarly, in a case where the obtained surrounding search data does not include dummy data, or in a case where the surrounding search data includes dummy data but the dummy data does not match the real data, the distance calculation means calculates a distance Li between the current location and each facility based on a route distance measured from the current position to each of the gas stations, by referring to the surrounding search data. The search means then conducts a search for gas stations in an ascending order of the distance Li between the current location and the facility, starting with a gas station having the shortest distance Li, based on the real data and the dummy data. The search result display means displays a list of the gas stations that have been found in the search. 
     As explained above, in the present embodiment, for each of the roads, the dummy data is generated for each of the facilities that are located within the surrounding search area AR 1 . In addition, with regard to the facilities that satisfy the data generation condition, dummy data is generated so that the facilities may be used as the targets for which the surrounding search is conducted. Thus, it is possible to easily conduct a search for the most appropriate facility for the driver, for example, a facility that the driver is able to reach in a short period of time. Consequently, it is possible to not only simplify operation of the input operating unit  34 , but also to enhance the level of efficiency of the search. 
     Further, for example, in a case where a certain facility is located on a general road within the surrounding search area AR 1  but does not satisfy the data generation condition, dummy data will not be generated, and the facility will not be used as the target for which the surrounding search is to be conducted. Thus, the facilities that are not reachable will not be displayed in a list as a search result. 
     Next, the flowchart in  FIG. 6  will be explained. 
     Step S 11 : Display all the categories. 
     Step S 12 : Select one of the categories. 
     Step S 13 : Judge whether a category including dummy data has been selected. In a case where a category including dummy data has been selected, the process proceeds to step S 14 . In a case where no category including dummy data has been selected, the process proceeds to step S 15 . 
     Step S 14 : Obtain surrounding search data. 
     Step S 15 : Obtain surrounding search data and proceed to step S 22 . 
     Step S 16 : Judge if there is any dummy data. If there is dummy data, the process proceeds to step S 17 . If there is no dummy data, the process proceeds to step S 22 . 
     Step S 17 : Compare dummy data with real data. 
     Step S 18 : Judge whether the dummy data matches the real data. In a case where the dummy data matches the real data, the process proceeds to step S 19 . In a case where the dummy data does not match the real data, the process proceeds to step S 22 . 
     Step S 19 : Judge whether each facility is located on the limited access road Hwi. In a case where the facility is located on the limited access road Hw 1 , the process proceeds to step S 20 . In a case where the facility is not located on the limited access road Hw 1 , the process proceeds to step S 21 . 
     Step S 20 : Execute an internal routine using the dummy data as real data. 
     Step S 21 : Execute an internal routine giving priority to the dummy data. 
     Step S 22 : Execute a distance calculation routine. 
     Step S 23 : Display the search results in a list, and the process ends. 
     In the present embodiment, the data generating apparatus  61  generates the surrounding search data; however, it is also possible to generate surrounding search data by using the CPU  31  or the CPU  54 . In the latter case, the CPU  31  or the CPU  54  includes a surrounding search data generation means, so that the surrounding search data generation means performs a surrounding search data generation process so as to generate the surrounding search data and to record the generated surrounding search data into the data recording unit  16 . 
     The surrounding search data obtainment means is included in a surrounding facility search means (i.e., a surrounding facility search processing unit). The surrounding facility search means executes a surrounding facility search routine to search for the facilities that are located in the surroundings (vicinity) of the current location. 
     In addition, while the vehicle is driven, the CPU  31  is able search for the facilities that are located in the vicinity of a current location, based on the data recorded in the data recording unit  16 . When the driver of the vehicle operates the input operating unit  34  ( FIG. 1 ) or the audio input unit  36  to request a search of the area AR 1  surrounding (on both sides on the searched route Rt ( FIG. 2 ), a facility search means (i.e., a facility search processing unit), that is included in the surrounding search processing unit  80 , executes a facility search routine to conduct a search for the facilities that are located in the vicinity of the current location, utilizing the facility data recorded in the data recording unit  16  based on the current location. Subsequently, a road judgment means (i.e., a road judgment processing unit), that is included in the surrounding search processing unit  80 , executes a road judgment process so as to judge whether the road on which the vehicle is currently being driven is a limited access road Hwi. When the road on which the vehicle is currently being driven is a limited access road Hwi, the distance calculation means calculates a distance Li between the current location and the facility as described above, based on the current location and the data recorded in the data recording unit  16 . 
     In the present embodiment, for example, in a case where a facility is located in a service area, like the gas stations GS 1 , GS 5 , and GS 6  shown in  FIG. 2  that are respectively located on the service roads Lw 1 , Lw 5 , and Lw 6 , because only dummy data is recorded as the surrounding search data for the gas station GS 6 , the distance L 6  between the current location and the facility is displayed with the symbol D appended thereto. On the other hand, for the gas stations GS 1  and GS 5 , both real data and dummy data are recorded as the surrounding search data, and an internal routine is executed using the dummy data as real data. Thus, the distances L 1  and L 5  between the current location and each facility are displayed without the symbol D appended 
     As a result, the driver will not be able to judge whether he/she should exit in order to use the gas station GS 1  or GS 5 . 
       FIG. 9  is a drawing that shows an example of a search result display screen according to a second embodiment of the present invention which addresses the foregoing problem. 
     In this second embodiment, for the gas stations GS 1  and GS 5 , in order to indicate that these gas stations are respectively located on the access (service) roads (rampways) Lw 1  and Lw 5  that are located in service areas of the searched route Rt ( FIG. 2 ), in other words, these gas stations are located on the limited access road Hw 1 , a symbol R is appended to the distances L 1  and L 5  between the current location and the facilities, as displayed. To generate such a display, the road judgment means judges whether the gas stations GS 1  and GS 5  are each located on the limited access road Hw 1  and forwards the result of the judgment to the search result display means. In a case where the gas stations GS 1  and/or GS 5  are located on the limited access road Hw 1 , the search result display means appends the symbol R to the distance L 1  and/or to the distance L 5  in order to indicate the judgment result. 
     In the embodiments described above, the surrounding search data is recorded on a disk; however, the surrounding search data may be recorded on any recording medium other than disks. 
     The present invention is not limited to the embodiments described above. It is possible to modify the present invention in various manners based on the gist of the present invention. Those modifications are not excluded from the scope of the present invention.