Navigation system for vehicles

Abstract: Geographical, guide or search information and route information are stored in storage sections 10 and 24. In order that an arithmetic section 20 may realize a route re-searching function in preference to the traveling direction of a vehicle, a route-calculating section 22 is equipped with a re-calculation section 22c for re-calculating the route, and a route guide control system 26 is equipped with a route deviation-detecting section 26b. The re-calculating section 22 calculates either the shortest route from the point of deviation to the previous route or a new route to the destination. In case of the search of the shortest route to the previous route, the shortest route from the present location to the previous route is searched in preference to the traveling direction (with no U-turn) on the basis of the search information of the periphery of the present location, so that the route to joint to the previous one can be quickly calculated. In case of search of a new route, the whole route from the present location to the destination is searched in preference to the traveling direction on the basis of the search information between the present location and the destination, to guide the driver along a route other than the previous one.

Description: The present invention relates to a navigation system for use in a vehicle to guide it to a destination through a preselected route and, more particularly, to a vehicular navigation system having a function to search the route, if missed to follow. A navigation system for use in a vehicle is equipped with a display device which is used when a route is to be determined, or a display device which is opened automatically or according to a driver's request while the vehicle is being guided by the navigation system. When conditions for determining an optimum route are inputted into a route setting map to start the route search, a detailed map containing the route (i.e., a route search map) is displayed. When the search is completed, a whole route map (i.e., a wide - area map)is opened in a form to permit the driver to clearly recognize the whole route. The driver can visually and aurally recognize from the whole route map only the route to travel from the present location to the destination. After this, the driver pushes a guide start button to initiate the guidance by means of the navigation system. The route may be missed to follow while the vehicle is traveling according to the road guidance. In order to prevent this failure, there is disclosed in JP-A-173815 /1989, for example, a function to instantly inform the driver of the deviation, if any, from the route thereby to re - search a new route. According to the method of the prior art, at the location where the driver recognizes that the vehicle goes out of the route, he or she is guided to search a new route to the destination. If this new route is not found out, the driver is guided to return the vehicle to the intersection where he or she missed the route. This may cause the driver to make a U - turn from the traveling direction so as to return to that location. For the driver, moreover, it takes a long time to search the route and is necessary to wait by stopping the vehicle. WO-A-9204683 discloses a navigation system allowing a recovery from an off-route condition. Thereby, a new route can be planned or the vehicle can be guided back to the preset route. The system only calculates a route from the present position to the destination of the vehicle. Due to this feature it is possible that a route going in the reverse direction of the travelling direction is calculated. If this is the case while the vehicle is travelling, a driver must bring the vehicle to a halt and make a U-turn. If the vehicle cannot be stopped immediately, it goes out of the newly searched route and new searching must be repeated. This can lead to a difficult situation for the driver. An object of the present invention is to provide a vehicular navigation system which re - searches only the periphery of a present location, if the route is missed to follow, so that the driver may be guided to search the shortest route from the present location to the initial route for a short time period. Another object of the present invention is to provide a vehicular navigation system for searching a new route in preference of the traveling direction to guide the driver in case of a deviation from the route. Still another object of the present invention is to provide a vehicular navigation system for selecting the shortest route to the initial one and a route other than the initial one conditionally automatically to guide the driver. The objects are obtained by the features of the claims. In order to achieve the above - specified objects, according to a first aspect of the present invention, there is provided a vehicular navigation system for automatically guiding a driver of a vehicle along a preselected route, which system comprises : storage means storing geographical information and search information of the periphery of a present location ; means for measuring the present location of the vehicle ; means for detecting a deviation of the vehicle from the route ; means for searching a route from the present location to the previous route, if the deviation from the route is detected, in preference to the traveling direction of the vehicle on the basis of said search information ; means for joining the searched route to the previous route to form a new route ; and means for controlling the guidance according to the new route. In the first aspect described above, according to a second aspect of the present invention, the storage means stores the geographical information and the search information between the present location and destination to search the whole route from the present location to the destination in preference to the traveling direction of the vehicle on the basis of said search information. According to a third aspect of the present invention, the vehicular navigation system further comprises: means for selecting the individual routes re - searched in the first and second aspects, according to input conditions or predetermined conditions; and means for controlling the guidance with the selected route. Fig. 1 is a block diagram illustrating a structure of a vehicular navigation system according to the present invention ; Fig. 2 is a diagram illustrating one example of a destination setting map on the display section of the system shown in Fig. 1 ; Fig. 3 is a diagram illustrating one example of a destination confirming map on the display section of the same system ; Fig. 4 is a flowchart for determining a display scale ; Fig. 5 is a flowchart for setting a final guide point ; Fig. 6 is a flow chart for searching a guide point; Fig. 7 is diagram illustrating one example of a section map on the display section of the same system ; Fig. 8 is a diagram illustrating one example of a section map on the display section if the vehicle fails to follow the route ; Fig. 9 is a diagram illustrating one example of a route research map on the display section of the same system ; Fig. 10 is a diagram illustrating one example of a whole route map on the display section of the same system after the route has been re - searched ; Fig. 11 is a flowchart illustrating a series of operations till the peripheral route re - calculations in a processing for searching the shortest route to a previous route ; Fig. 12 is a flowchart for re - calculating the peripheral routes; Fig. 13 is a flowchart for calculating traveling directions and penalties at each intersection toward the previous route ; Fig. 14 is a flowchart to be continued to Fig. 20; Fig. 15 is a diagram for explaining the contents of the individual operations in the peripheral route re - calculations ; Fig. 16 is a flowchart for re - searching other routes ; Fig. 17 is a flowchart for calculating the whole route when the traveling direction is considered ; Fig. 18 is a flowchart for calculating the whole route when the traveling direction is not considered ; Fig. 19 is a diagram illustrating one example of a route search map on the display section of the same system ; and Fig. 20 is a flow chart for automatically selecting a search for the shortest route to the previous route and a search for a novel one from all routes. The present invention will be described in the following in connection with the embodiments thereof with reference to the accompanying drawings. Fig. 1 shows a hardware structure of a vehicular navigation system according to the present invention. This navigation system comprises : a geographical information storage section 10 storing navigation data necessary for calculating routes, guide data necessary for guiding the driver of the vehicle, and other kinds of data ; an arithmetic section 20 for controlling the whole system; a vocal control section 30 for converting speech data into an analog signal according to instructions from the arithmetic section 20 and for driving a loudspeaker 34 to provide a guide voice for guiding the driver ; a display section 28 for displaying a route automatically or in response to a request of the driver ; an input section 19 for entering a destination or requesting the guidance of a route ; a present position - measuring section 12 for determining the present position of the vehicle; and a route memorizing section 24 for storing the route data which are calculated by the arithmetic section 20 according to the destination. The geographical information storage section 10 offers a database in which all the data including geographical data necessary for guidance along a route, data used to provide displays for guiding the driver, and other data are stored. Of these data, the data about a point, in which a final guide point is registered in advance in the system with respect to the destination to be set, are stored in a registered data storage section 10a, and the data necessary for searching the route are stored in a search data storage section 10b. The present position - measuring section 12 determines the present position of the vehicle from the position information and azimuth information which are received by a GPS receiver 14 employing the global positioning system (GPS), the azimuth information which is obtained by a direction sensor 16, the distance information which is obtained by a distance sensor 18, and the geographical information which is read from the geographical information storage section 10. The present position - measuring section 12 sends the present position information thus obtained to the arithmetic section 20. Here, the direction sensor 16 determines the direction in which the vehicle is to travel, from the geomagnetism and the relative azimuth of the vehicle. The distance sensor 18 determines the distance traveled by the vehicle, from the number of revolutions of the wheels. The input section 19 instructs the arithmetic section 20 to perform the processing operations necessary for navigations in accordance with the driver's request. For these operations, through the input section 19, the driver enters a destination and route setting conditions, changes and enters a selected destination, instructs a research, or allows the driver to achieve the guide information by means of a speech and/or visual display if required by the driver. The arithmetic section 20 comprises a route - calculating section 22 and a route guide control section 26. The route - calculating section 22 sets the final guide point, if any, which is either obtained by calculations on the basis of the destination setting information or preset. The route - calculating section 22 further calculates a route to the destination according to the geographical information read from the geographical information storage section 10 and according to the present position information from the present position-measuring section 12. The route ― calculating section 22 then loads the data about this final guide point into the route memorizing section 24. On the other hand, the route guide control section 26 produces a vocal and/or visual display automatically or according to the request signal, depending upon the guide information stored in the geographical information storage section 10, the present position information and the route information. The route - calculating section 22 includes : an initial calculation section 22b for initially calculating the whole route from the starting point to the guide point; a guide point - setting section 22a for setting the guide point after the destination has been set ; and a re - calculation section 22c acting as means for realizing a function. This is a re - calculating function for determining the route to the destination from the route, which has been deviated by the predetermined route search method, in accordance with the route research instruction from the input section 19 on the basis of the detection of the route deviation from the route guide control section 26. When the guide point is set relative to the destination by the route - calculating section 22 by loading the destination into the destination setting map, the route guide control section 26 outputs the display instruction of the destination confirming map, which is formed with a destination mark for confirming the destination and a guide point mark, to the display section 28. If the destination is confirmed in this map, the route search is started so that the display instruction of the selected route is fed to the display section 28 and is displayed in the whole route map. This route guide control section 26 includes: a display scale - determining section 26a and a route deviation - detecting section 26b. The display scale - determining section 26a acts as means for realizing a display scale determining function to determine the scale of a map from the distance between the two positions so as to display the set destination and the final guide point in a common map. The route deviation - detecting section 26b detects from the positional deviation and azimuth deviation between the selected route and the present position that the vehicle is traveling apart from the route. If this deviation is detected by the route deviation detecting section 26b, the display of a guide stop button 128b goes out of the section map, as shown in Fig. 7. Specifically, the guide interrupting function is stopped, and a re-search button 128d shown in Fig. 8 is displayed to urge the driver to search the route again from the point of route deviation. This route deviation detection can resort to the method disclosed in Japanese Patent Laid - Open No. 173815/1989, for example. The display section 28 consists of a color CRT or color liquid - crystal display and is mounted in the instrument panel near the driver's seat. The driver can confirm the present location of the vehicle by observing a section map or an intersection map. The driver can also obtain information about a forthcoming route. Furthermore, the driver confirms intersections at which the vehicle should turn, as well as the direction of the route, i.e., whether the vehicle should turn to the right or to the left at the intersections. All maps necessary for navigation such as a route - setting map based on the geographical data and guide data processed by the route guide control section 26, a route search map, a route re - search map, a whole route map, local maps, intersection maps, and arrival guide maps are presented in the display section 28 in color. The display section 28 is equipped with function buttons to set the route guidance and to switch the displayed map to another during the guidance. In particular, the display section 28 has a touch screen corresponding to the displayed buttons. The aforementioned operations are carried out according to a signal entered by touching the buttons. These buttons, the touch screen and the like together construct input signal generating means, which forms the input section 19. Detailed description of this input section 19 is omitted because the structure of this section is known in the art. In a destination setting map 40 to be opened by selecting a destination from a menu frame, as shown in Fig. 2, there are displayed a map around the destination and a cursor 41 which is located on the destination. By touching a triangle key 41a of the cursor, this cursor 41 is moved in the direction of the touched triangle key. The display of this cursor 41 is controlled by the input section 19. The cursor 41 is operated to bring its center to a predetermined position around the destination such as a parking area if the destination is a golf course, and a location setting button 42 is pushed. Then, the guide point is located, and the map is changed, if located, to a destination confirming map 50, as shown in Fig. 3. On this destination confirming map 50, there are displayed not only a designated destination mark 51 and a guide point 52 on a road but also a message "Guide to location" for guidance to the final guide point 52. This map 50 is further displayed with a "Yes" button 53 and a "No" button 54 for confirming the destination and the guide point. If the "Yes" button 53 is pushed, there are fixed the destination 51 and the guide point 52, as displayed on the map. Here will be described a function to display on a common map both the destination and the final guide point in the route guide control section 26. Fig. 4 is a flowchart illustrating a series of operations to be carried out for the display processing. Destination coordinates (Dx,Dy) and final guide location coordinates (Ax,Ay) are obtained (at S1 and S2) to calculate (at S3) the distance Dis = √ ((Dx - Ax) 2 + (Dy - Ay) 2 ) between the destination coordinates and the final guide location coordinates. A minimum scale admitting twice of Dist is searched (at S4). A map is drawn (at S5) around the destination coordinates. This display is the destination setting map. Here, the "obtain" means a processing for calculating the coordinates from the position indicated on the map. Here will be described the guide location setting function of the route calculating section 22. Fig. 5 is a flowchart illustrating a series of operations to be carried out for setting the final guide point. Fig. 6 is a flowchart illustrating a series of operations to be carried out for searching a point on a road close to the set destination (as will be referred to as the "search flow"). When the setting of a destination is completed on the destination setting map, the flow for setting the final guide point is started. First of all, it is decided (at S10) whether or not the registered location data are used. If NO, the search flow is executed. If the registered location data are used, it is decided (at S11) whether or not the cursor has been moved a predetermined distance or more. If YES, it is decided that the destination is different from the registered location, and a point on a road close to the set destination is searched. If the cursor movement is within the predetermined distance, the registered location data are set to a final guide location (at S12) and are stored in the route memorizing section 24. On the basis of the registered location data, the route guide control section 26 outputs the display instruction of the final guide location mark to the display section 28. When a later - described search flow is executed to set the guide location or not, it is decided (at S14) whether or not the guide location is. If NO, the routine is ended. If YES, it is decided (at S15) whether or not an intersection is within a predetermined distance. If YES, the intersection is set (at S16) to the final guide location. If NO, on the other hand, a point on the searched road is set to the final guide location (S17). Here will be described the search for the guide location. First of all, roads within a predetermined distance from the destination are detected (at S20), and a living road such as a lane allowing no facing traffic or a school attending course is eliminated (at S21) from the roads. Then, a perpendicular is drawn (at S22) from the destination to the road, to detect the nearest point. Since there may be a plurality of near points detected, their number is decided (at S23). If the points are in plurality, either the point near the present location or the point initially detected is tentatively set (at S24) to the guide location. If only one, on the other hand, the near point is tentatively set (at S25) to the guide location. It is decided (at S26) whether or not there is a road to be entered to the tentatively set guide location. If YES, this guide location is set (at S27) to the final one. Otherwise, a next near point is calculated (at S28), and the result is decided (at S29). In other words, the routine is ended if the next near point is absent. If this next near point is present, on the other hand, the routine is returned to S23, at which the number of the near points is decided to set the guide location tentatively. From now on, the routine of S26 to S29 is likewise executed. According to the present embodiment, in case an arbitrary location is selected for the destination from the detailed map, the arithmetic operations are started from the position of the destination to set the final guide location. On the other hand, in case the destination is selected from the menu frame and is set by moving the cursor in the map shown in Fig. 2, the final guide location for the initial destination is set if the moving distance of the destination set from the initial destination is within the predetermined range. Otherwise, the final guide location is set by the arithmetic processing from the position of the destination. In the absence of the registered location data or in case the destination is changed on the destination setting map, the guide location is searched. In case the destination is selected from the menu, it is also possible to set the preset final guide location. If the destination is a CO golf course, for example, the system is stored in advance with a ΔΔ intersection or an intermediate point of the road as the final guide location. Thus, if the destination is set, the final guide location corresponding to the destination input on the basis of the registered location information is set, and the destination and the final guide location are displayed on the map. Whether the destination and the final guide location are in common or different positions can be confirmed by observing the map, and the optimum final guide location for the destination can be guided by setting the final guide location on the basis of the registered location information. In case the scale of displaying the destination and the final guide location on a common map is automatically selected, the departure and direction of the final guide location from the destination can be visually and aurally confirmed. Incidentally, a section map 60 to be displayed after the start of guidance is displayed, as shown in Fig. 7, with a route 101, a road 102 other than the route, and a vehicle mark 104 and a traveling direction mark 106 on the route. The section map 60 is further displayed with function buttons 128 for making accesses. In the present example, the map is formed with the route 101 in red, a detail button 128a for enlarging a local area, a guidance stop button 128b for stopping the guidance, and a wide - area button 128c for displaying the whole route. If the deviation from the route exceeds a predetermined distance during the guidance, the guidance stop button 128b disappears, and the map changes to a section map 60A which is displayed with a re-search button 128d, as shown in Fig. 8. If this re - search button 128d is pushed, the route re - search is started, and a route re - search map 70 shown in Fig. 9 is opened to display the indication of "Searching". This map is further displayed with a reset button 128e for fixing the searched route. If this reset button 128e is pushed, a newly fixed map 80 of the whole route is opened, as shown in Fig. 10. In the present example, a new route to point A is displayed as the route closest to the initial one from the point of deviation, in addition to the previous route. If a guidance start button 128f is pushed, the guidance is started again. The vocal control section 30 synthesizes the voice, phrase, one sentence, sound and so on, which is read from a vocal storage section 32, in response to a vocal guide instruction from the route guide control section 26, and outputs it from the speaker 34. The vocal storage section 32 stores, in a compressed state, the vocal guide data such as the operation guidance for setting the route and the names of landmarks on the route, or the vocal guide data necessary for the vocal guidance during the route guidance. Furthermore, the vocal control section 30 outputs the landmark names, which are displayed in the whole route map, vocally from the speaker 34 when the whole route map is instructed and displayed from the route guide control section 26. In the present example, the vocal guidance of a landmark to be outputted is exemplified by "Route through Nagoya Interchange of Tollway". Here will be described the processing for re - searching the route if missed to follow. Fig. 11 is a flowchart illustrating a first embodiment of the route re - search. The present embodiment is characterized in the route search for effecting a quick join not into the initial route preferred to the shortest distance but the initial route preferred to the traveling direction of the vehicle in case of a deviation from the route. Here, the deviation from the route is detected by a timer interruption. If the route deviation is detected (at S30), the re ― search button is displayed (at S31), as shown in Fig. 8. It is then decided (at S32) whether or not the vehicle is on route. The correct route may be restored as soon as the route deviation is perceived. In this case, the "on route" is decided (at S32), and the re ― search button is deleted (at S33), and the routine is returned to S30. On condition the deviation from the route, it is decided (at S34) whether the re - search button has been pushed. If NO, it is decided again (at S32) whether the vehicle is on route. When the re - search button is pushed ON, the re - calculation routine of the peripheral route is started. Fig. 12 is a flowchart illustrating a series of operations to be carried out in the out in peripheral route re - calculating routine. Figs. 13 and 14 are flowcharts are illustrating a routine for calculating the traveling direction and penalties at each intersection back to the previous route. Fig. 15 illustrates the processing contents of the individual steps in the peripheral routs re - calculations. When the peripheral route re - calculation routine is started, the search data around the present location of the vehicle are read (at S35) (as illustrated at (1) in Fig. 15) at first from the registered data storage section 10b of the geographical information storage section 10. And, the road array data of the route (as will be referred to the "previous route"), along which the vehicle has been guided before it misses the route, are obtained (at S36) (as illustrated at (2) in Fig. 15) from the route memorizing section 24. Incidentally, the route is defined as the road array (as indicated by arrows on the route) obtained by joining the roads between the intersections. Moreover, the word "obtain" is to copy the data into the work area of the route-calculating section 22 from the route memorizing section 24. Then, the traveling direction and penalties at each intersection back to the previous route are calculated (as illustrated at (3) in Fig. 15). Specifically, all the intersections around the present location are initialized (at S40) to set the status flag to "not searched yet", the penalties to " ∞ " and the traveling direction to "No". The traveling direction and penalties are set on the previous route around the present location (at S41) to keep each intersection searched. It is decided (at S42) whether any intersection being searched. If YES, the intersection having the minimum penalties is found (at S43). If this intersection is found, the status flag of a pertinent intersection is changed to the searched status (at S44). The penalties at the intersection jointed to that pertinent one are calculated (at S45). These penalties are calculated in terms of the distance, the road width, signals, rightward or leftward turns and so on. If the roads are not joined in the presence of marks of "No Admittance" or "One Way" or at the time of a "U-turn", the penalties are calculated to "∞". It is decided (at S46) whether or not the calculated penalties are smaller than the previous ones. If NO, it is decided (at S51) whether or not there is another joined intersection. If YES, the penalties are updated (at S47), and the traveling direction is updated (at S48). It is decided (at S49) whether or not the status flag of the joined intersection is being searched. If YES, it is further decided (at S51) whether or not there is another joined intersection. If the joined intersection is not being searched, the status flag of this intersection is changed to being searched (S50). After this, it is decided (at S51) whether or not there is another joined intersection. If this answer is YES, the routine is returned to S45, at which the penalties of the intersection joined to the existing intersection are calculated so that the operations of S46 to S51 are carried out according to the calculated result. In the absence of any other joined intersection, the routine is returned to S42, at which it is ended by deciding whether or not any intersection is being searched. Reverting to the routine of Fig. 12, the present road and traveling direction of the vehicle are obtained (at S37) (as illustrated at (4) in Fig. 15) on the basis of the information of the present location from the present position - measuring section 12 and the geographical information from the geographical information storage section 10. Subsequently, on the basis of the traveling direction at each intersection, which was calculated by the operations of Figs. 13 and 14, a search is made (at S38) (as illustrated at (5) in Fig. 15) from the present location to the previous route. The road array of the searched route (or new route) and the previous route is formed (at S39) (as illustrated at (6) in Fig. 15) as a forthcoming guide route. On the basis of this road array thus re - formed, the route data for calculations stored in the route memorizing section 24 are set, and the new guidance is then started. Fig. 16 is a flowchart illustrating a second embodiment of the route re - searching routine. The present embodiment is characterized in the route search considering not the initial route but the traveling direction in case of a deviation from the route. This route re ― search is operated in a route re - search map 90 which is used for setting the route 90, as shown in Fig. 19. This map 90 is displayed with a search button 128g for instructing an execution of the route search. First of all, it is decided (at S60) whether or not an effective route is stored at present in the route memorizing section 24. If NO, it is decided (at S61) whether or not the search button has been pushed. If this button is not pushed, the routine is ended. If the button is pushed, on the other hand, it is decided (at S62) whether the vehicle is traveling. If YES, the whole route calculating routine considering the traveling direction (as will be called the "first whole route calculating routine") is started. If the vehicle is not traveling, it is decided (at S63) whether the vehicle is on route. If YES, that is, if the vehicle stands still on the road, the first whole route calculating routine is started. Otherwise, that is, if the vehicle is off the road or in a parking area or a private place, a whole route calculating routine considering no traveling direction (as will be called the "second whole route calculating routine") is started. If there is a route at the aforementioned S60, the guidance stop button is pushed, and it is decided (at S64) whether or not it is in the guidance stop mode. If YES, the re - search button is displayed (at S67) in the route search map. If not in the guidance stop mode, it is decided (at S65) whether or not on route. If YES, the re-search button is deleted (at S66), and this routine is ended. If not on route, on the other hand, the re-search button is displayed (at S67), and it is decided (at S68) whether the same button has been pushed. If YES, the first whole route calculating routine is started. If not pushed yet, this routine is ended. Here will be described the first whole route calculating routine with reference to Fig. 17. First of all, the present road and traveling direction are obtained (at S70) from the present location information and the geographical information, and the destination road is obtained (at S71) from the destination information inputted and the geographical information. Next, the search data from the present location to the destination are read (at S72), and the intermediate route is re-calculated and searched (at S73). The subsequent operation map is displayed like the foregoing first embodiment. Here will be described the second whole route calculating routine with reference to Fig. 18. First of all, the present road is obtained (at S80) from the present location information and the geographical information, and the destination road is obtained (at S81) from the destination information inputted and the geographical information. Next, the search data between the present location to the destination are read (at S82), and the intermediate route is recalculated and searched (at S83). The subsequent operation map is displayed like the foregoing first embodiment. Fig. 20 is a flowchart illustrating a third embodiment of the route re - searching routine. The present embodiment is characterized in the conditioned proper use of the first route search considering not the first route but the traveling direction and the second route search considering not the first route but the traveling direction, in case the vehicle deviates from the route. Incidentally, the first route search uses the steps S30 to S34 of the first embodiment, as shown in Fig. 11, and the peripheral route re - calculating routine, as shown in Fig. 12, whereas the second route search uses the whole route recalculating routine, as shown in Fig. 18. Hence, their contents will not be described here. At first, the first route searching routine is executed to re - calculate the peripheral route. From this result, it is decided (at S300) whether the route has been searched. If YES, the search by the routine is ended. On the other hand, in case the route cannot be searched because the road is closed, the second route search is executed to re - calculate the whole route. If a route is resultantly searched, the search by the routine is ended. In the present embodiment, it is decided as the setting condition for the present system whether or not the route could be searched. In addition, the condition for this decision may use the route closer to the destination, for example. Moreover, a prepared condition can be selected and inputted to the route re - search map. As now apparent from the description thus far made, the following effects can be achieved according to the present invention : (1) If a deviation from the route is detected, the stored search information of the periphery of the present location is read out, and the search from the present location to the previous route is executed while considering the previous route road array, the present road and the vehicular traveling direction, so that a route to join the previous route can be quickly calculated by joining the searched route to the previous one. (2) In preference to the vehicular traveling direction based on the search information between the present location and the destination, the whole route from the present location to the destination is searched to guide the driver along a route other than the previous one. As a result, the driver can search another route while intentionally missing the route according to the road circumstances as when the vehicle is difficult to find its way due to the stagnant traffic or under construction or while traveling another route. Without this function, the driver would be required to search the route by re - inputting the present location and the destination at a position off the route. (3) The route to joint to the previous one found by searching it around the present location and the new route by the whole route search are automatically selected according to either the condition inputted by the driver himself or the preset condition. For example, if the driver recognizes that the vehicle has been missed to follow the route and selects the re ― searching function, the present system searches the route for returning to the previous route as soon as possible in preference to the traveling direction of the vehicle. In case, however, the peripheral search of the location off the route has found the absence of the route back to the previous one, the present system automatically searches a route other than the previous one in preference to the vehicular traveling direction. Thanks to this route search, the guidance to the destination is re-opened without stopping the vehicle.

Claims: Navigation system for providing a route guidance to a destination in accordance with a preset route, comprising: a) means (10) for storing geographical information and search information; b) means (12) for measuring the present position and the travelling direction of the vehicle; c) means (26b) for detecting a deviation of the vehicle from the route; d) means (22c) for searching a new route if a deviation from the route is detected; e) means (26) for controlling the guidance according to the new route; characterized in that f) said new route is selected to be in the travelling direction of the vehicle and to prevent the vehicle from making a U-turn. Apparatus according to claim 1, characterized in that the means (22c) for searching a new route searches a route from the present position of the vehicle to the preset route, connects the searched route to the preset route and makes a first new route. Apparatus according to claim 1, characterized in that the means (22c) for searching a new route searches a whole route from the present position to the new destination as a second new route. Apparatus according to claims 1 and 3, characterized in that means are provided to select the first new route or the second new route on the basis of an input condition or setting condition. Apparatus according to any of claims 1 to 4, characterized in that the means (22c) for searching a route specifies the direction of the road on which a vehicle is travelling by the detected travelling direction of the vehicle.

Inventors: MAEKAWA KAZUTERU, MASUDA HIROYOSHI, MORIMOTO KYOUMI, NIMURA MITSUHIRO, OHARA SHIGEKAZU, MAEKAWA, KAZUTERU, MASUDA, HIROYOSHI, MORIMOTO, KYOUMI, NIMURA, MITSUHIRO, OHARA, SHIGEKAZU
Applicants: AISIN AW CO, AISIN AW CO., LTD.
Application year: 1993
Main classification: G08G1
IPC codes: G01C21, G05D1