FR2743655A1 - Route selection method for road-bound vehicle - Google Patents

Abstract

The method uses guidance equipment comprising calculator (16), a vehicle localisation module (11), a data base memory (12), controls (13,14) and a guidance display (15), and the guidance includes three phases which are from departure to principal road network, across road network and from road network to destination. During the initial phase the guidance indicates the course and distance as the crow flies to the road network intersection. While driving across the principal network information is given on negotiating crossroads so that an optimised route is followed. During the last phase from principal network to destination the course and distance as the crow flies to the destination is given.

Description

 The present invention relates to the technical field of aid to the navigation of road vehicles. More specifically, this invention relates to a method of guiding a road vehicle, based on the determination of the instantaneous position of the vehicle, on the optimization of a route making it possible to reach a chosen destination, and on the indication in time. of the direction to follow to respect this itinerary.

 Guidance systems are known in the state of the art, offering the possibility of entering a destination, performing a route calculation, and giving guidance indications at the intersections encountered, until the final destination.

 Certain known embodiments also offer the display, on an orientable base map, of the calculated route, and the automatic calculation of a new route from the detection by the system that the vehicle has been diverted from the route initially indicated.

 The architecture of a known system comprising these functionalities can be autonomous, the necessary database being contained in the on-board system, as in the system called CARI N, or dependent on an infrastructure, for example of beacons located on the edge of channel and transmitting cartographic information, as in the case of the EUROSCOUT system, or of a radiotelephone allowing the reception in the vehicle of transmitted cartographic information, as is the case for another known system.

 However, the systems proposed so far have a number of drawbacks.

 Among the guidance systems using a database describing the road network, there is the family of exhaustive database systems, which are expensive, due to their hardware requirements: a CD-ROM drive, lots of RAM. , and a powerful calculator to manage all this data. There are also simplified database systems, which are less expensive, but offer a limited service, since they are only capable of guiding towards a main node of the road network.

 A specific example of such a simplified database system is described in document EP-A0,595,685. This document describes a device for guiding a vehicle using an imprecise location, of the order of 100 meters, by GPS ("Global Positioning System") satellites, which is satisfied with a non-exhaustive road network database. , describing the traffic plan in a simplified way. This system guides the user on this network from node to node, up to the last node belonging to the programmed destination. However, considering the poor accuracy of the location module, this process limits the type of destinations likely to be reached in built-up areas, as well as in remarkable places and sites containing nodes in the network, but in particular excluding guidance to a street particular.

 A second series of limitations concerns the quality of vehicle guidance and associated indications.

 Firstly, guidance in complex crossroads is not satisfactory, both from an ergonomic and safety point of view and from the point of view of guiding efficiency. Guidance is based on geometric information: for complex intersections, the geometry of the intersection is presented to the driver in particular in a sparse and stylized form, on a screen, with an indication of the progress of the vehicle. However, these indications correspond to an aerial view of the crossroads, which the driver may have difficulty interpreting, which leads him to make tracking errors. In addition, a complex crossroads is made up of a succession of linked bifurcations, which means that the succession of announcements and displays by the system is not precise enough to avoid confusion. The disadvantages that can result are obvious: routing error in a complex crossroads can lead to a fast lane or even a motorway, which imposes a significant detour or generates dangerous maneuvers to avoid the detour, such as reversing on access ramps.

 On the other hand, the guidance offered along routes composed of simple crossroads is on the contrary too detailed: the guidance messages are too numerous and unnecessary, which can lead to rejection of the system by the driver.

 Secondly, the existing systems have shortcomings with regard to the choice of the route itself. Indeed, they determine a route using a set of criteria such as the distance to be covered, the speed allowed, or the tolls to be paid, criteria among which the driver sets his priorities. However, the data to calculate the route using these criteria are contained in the system memory, and are not updated according to external hazards, such as the announcement of a traffic jam on an axis, or a temporary message from road safety or traffic planning, available on a display panel or on the radio.

 Therefore, the invention aims to provide a method and a device for overcoming all of the above drawbacks.

 In particular, the present invention proposes to extend to any type of destination, including an address on a street, simplified network guidance on a road network, while using a low cost guidance device.

 Another object of the invention is to propose a system having good ergonomics of use, both for guiding towards main nodes of a road network as for secondary axes or city streets.

 To this end, the invention relates to a method of guiding a road vehicle, based on the determination of the instantaneous position of the vehicle, on the optimization of a route making it possible to reach a chosen destination, and on the indication in real time of the direction to follow to respect this route, characterized in that the calculation of the route to be followed includes a phase taking into account the main traffic lanes, so as to determine an optimized route with respect to these main lanes , and at least one phase known as bird's-eye guidance or compass guidance, on secondary traffic lanes, consisting simply of the real-time indication of the position of a point to be reached represented in double form a direction relative to the instantaneous heading of the vehicle and the distance as the crow flies between the instantaneous position of the vehicle and the point to be reached, this point being a crossroads of the main network or, in the final phase, the destination to reach itself. Advantageously, throughout the various guidance phases, information on the remaining distance (as the crow flies or along the route) and information on the course of the destination can be presented additionally.

 According to other characteristics of the guidance method according to the invention: the calculation of the route comprises a street-by-street guidance phase from a starting point to the point closest to the main network, and a phase of street-by-street guidance between the node of the main network closest to the destination, and the destination. Advantageously, the street-by-street guidance phase from the starting point to the main network and from the last node of the main network to the destination uses remaining distance information and information on the heading of the destination.

 In addition, the guidance phase on the axes of the main network is based on directional guidance at a plurality of complex intersections placed at the intersections of these axes, and directional guidance at the level of complex intersections is combined with non-guidance intrusive based on the indication of only route changes.

 Preferably, guidance in complex intersections uses the two names of the directions corresponding to the axis to be taken, the name of this axis, and an indication of a global direction to take, expressed angularly with respect to the axis. longitudinal of the vehicle, and between two complex crossroads, the only guidance indication is the name or the road nomenclature of the current road. Advantageously, the guidance indications at the level of the complex intersections where the arrival takes place on several queues, are supplemented by preliminary announcements capable of ensuring correct positioning with respect to these queues. The messages can advantageously refer to road works for a better understanding by the user, for example: turn left to take the flyover.

 The invention also relates to a guidance device, adapted in particular for the implementation of the guidance process mentioned above, and characterized in that it comprises, connected to a computing unit, a location module, a memory medium containing guidance databases, one or more control devices for programming the destination, and a device for presenting guidance information to the user.

 Preferably, the guidance database comprises a first database corresponding to the main traffic lanes, and a second database corresponding to secondary lanes, these databases being possibly simplified, and stored in a compressed form having a low memory footprint.

The invention will be better understood by referring to the following description given by way of nonlimiting example and to the attached drawings, in which:
- Figure 1 shows schematically a destination to reach, away from a main road network;
- Figure 2 shows schematically the principle of programming using an address of the destination, using the navigation device according to the invention;
- Figure 3 shows schematically the programming phase using a map of the destination, using the device and the navigation method according to the invention;
- Figure 4 shows schematically an example of guidance near the destination, using the method according to the invention;
- Figure 5 shows a block diagram of the architecture of a navigation device capable of implementing the method according to the invention.

 - Figure 6 shows the sequence of display of messages by the navigation device, when hooking and crossing a crossroads.

 The underlying principle of the method and of the guiding device according to the invention consists in structuring the road axes database into two distinct levels, preferably using two distinct databases: a first database containing the simplified information of the main road network, and a second database containing the final destinations in simplified form.

 The first database or the first level allows the calculation of a route and the guidance from an initial node of the route calculated on this network, close to the starting point, to a final node of the route on this network, close to the finish. The second database allows the programming of the destinations and the final guidance of the last node of the network towards the destination. The invention also provides several programming and guidance modes for the destination, depending on the guidance databases used.

 According to the invention, the two guidance databases are preferably simplified by the use of an absolute location module by satellites or by terrestrial beacons, not requiring additional cartographic data for the calculation of the positions, unlike to the known technique of registration on digital vectorized card, called map-matching.

 Furthermore, the final guidance method is such that it allows the user to be guided even to a given destination in the form of an address on a particular street, despite the accuracy of the location module which is only 1 'order of a hundred meters.

 The advantage is that only the minimum information necessary for each stage is stored in the system (destination programming, route calculation, guidance on the simplified road network, and final guidance to the destination), all preserving the universality of the choice of possible destinations.

 In particular, the database of streets used for programming the destination can be stored in a compressed form. When used, the data in the desired area is temporarily decompressed into RAM. Then we can free this memory when the system carries out the actual guidance. In addition, since this street base is not used for actual guidance, it does not need to be organized in a network, but can simply be represented as lists of street names or nomenclatures.

 We thus arrive at a simplified guide service, less expensive but nevertheless effective.

 The main network can be established by taking into account on the one hand the main traffic lanes (motorways, national and departmental roads), and on the other hand, in agglomerations, the main network is based on known traffic patterns such than established by cities or administrations.

 To take into account the main traffic lanes, route arrows using these lanes are used, as established by the authorities to indicate the recommended routes. These arrows use, in a known manner, the names of neighboring localities or larger distant urban centers.

 By way of example of a main network within the meaning of the invention, mention may be made of the main circulation network of the Paris region, which comprises approximately 900 to 1000 intersections of axes retained in the main network.

 The database being correctly structured in two levels, the guidance method provides for calculating a route which is based on the main traffic network, so that the resulting route includes an initial guidance phase in flight from bird to the main network, followed by an intermediate guidance phase on the main network, and finally a final bird's-eye guidance phase to the destination.

 Of course, depending on the starting point and the destination, one or more of these stages can be rendered useless. However, this description is made in the context of the most general problem to be solved, in which neither the starting point nor the destination correspond to a point on the main network. An example of a main network 1 comprising nodes 2 is shown in FIG. 1, also showing a destination 3 away from the main road network 1.

 The method according to the invention makes it possible to reach destinations 3 different from the nodes 2 of the main network 1, and the route is then described, apart from the departure and arrival phases, by a succession of classified routes (A for the motorways, N for national roads), or a succession of main streets for built-up areas (figure 2), including street 20 containing destination 3 if applicable.

 Guidance on the axes of the main network 1 is based on directional guidance at the level of the main intersections, and in particular of the complex intersections of these axes, preferably combined with non-intrusive guidance based on the indication of changes in direction. These methods are explained in more detail below.

 Complex crossroads, in which the geometric type of guidance is difficult to use as indicated above, are in particular urban crossroads with entrances or exits to expressways.

 As an example, we can consider that in the Paris region, there are a hundred complex crossroads, such as those at Porte de Bercy, Porte de la Chapelle, or the crossroads at Pont de Sèvres.

 In such a crossroads, the invention provides guidance using the two names of the directions corresponding to the axis to be taken, the name of this axis, and possibly an indication of a global direction to take, expressed angularly or graphically by relative to the longitudinal axis of the vehicle: for example straight ahead, 45 to the right, etc. Of course, this indication of overall direction is constantly updated according to the rotations of the vehicle around an axis vertical.

 Such an indication of a global direction used at the level of complex crossroads makes it possible to limit the number of roads which can a priori correspond to the exit axis of the crossroad which is targeted, the final choice of this exit axis being confirmed by the presence road signs corresponding to the names of direction or road axes mentioned above.

 Such a guiding method is particularly suitable for roundabouts of the roundabout type with many branches.

 It should be noted that for interchange type crossroads, the indication of overall direction is not useful as real-time guidance, since the direction of exit from the crossroads corresponds to that of an access ramp of the 'target axis, which at the beginning does not coincide with the direction of this axis.

However, in these configurations, the indication of overall direction can be used to verify with a slight time shift, that the driver has taken the correct axis. For this purpose, in the case of an exchanger, the indication of overall direction is displayed only after the crossing of the decision points of the crossroads, only the names of the two directions of the axis and the name of the axis being displayed before these points.

 In a useful way, the guidance indications at the level of the complex intersections can be supplemented by preliminary announcements making it possible to ensure correct positioning with respect to the queues, in the event that the arrival at the intersection is made on several queues.

 It should be noted that for a given exit axis from a complex intersection, the main network database may contain a greater number of panels present on the ground, than simply the two panels of the directions indicated to the driver. The choice of signs indicated by the system is then based on the criteria of first indicating the most visible signs on the ground (for example, in France, the blue signs of motorways or the green signs of intercity axes), and preferably indicate the panels ensuring continuity of display with the next intersection on the calculated route.

 The method according to the invention preferably provides that the guidance indications based on the directions to be followed, are only valid at crossroads. In this case, they are not displayed after leaving the crossroads, when the vehicle is engaged on the correct route. At this stage, the only remaining indication is the name of the current road, indicated in the form of road nomenclature, or failing that by its name.

However, if one of the directions announced remains valid at the next intersection, it can be kept displayed.

 The advantage of the guidance method indicated above resides in the fact that it is based on natural guidance principles and reproduces an intuitive way of guiding, in the absence of an on-board guidance system. These principles are easy to implement in a real way by users on the road network, and in particular at the level of complex crossroads. Indeed, in these environments, where signage is abundant, it is useful for the system to indicate only the most effective information, and this from the possible prepositioning in the right queues. In addition, the indications given in the form above are easy to memorize, so that the driver does not need to frequently look at the display screen to understand the guidance instructions.

According to another advantageous characteristic of the guidance method according to the invention as implemented on the main network, so-called non-intrusive guidance is used, which is based on the following principles:
- the system announces a route only in the event of a change of road name, and there is no announcement if only the name of the direction changes;
- when several routes with different names are grouped under the same road entity, seen by the user, there is no announcement when the route changes (for example the A104 and N444 are different routes; but there is no '' there is no announcement because they are part of the same road entity seen in particular by the user: the Francilienne).

- on a given road, the direction is only announced in the event of the possibility of confusion, for example when the current road leads to a crossroads giving on the continuation of this road and on another road;
- a pre-positioning announcement is made if necessary, and constitutes an exception to the principle of non-intrusive guidance.

The user also has the possibility of requesting voice information adapted to the context in which the system is located, allowing him a more flexible use of the system. Thus, near the crossroads, the voice information relates to the immediately necessary guidance indications. Between two crossroads, the voice information relates to the next indications to be followed at the end of the current road. This process can be implemented in a set of two commands
- the first is used to ask the system what to do immediately at the crossroads, the system tells the overall direction to follow (heading information); between two crossroads, it tells the current direction to follow.

 - the second is used to ask what will soon be done: at the crossroads, the system tells the direction and the route to follow (text information on the signs); between two crossroads, it says the next indications which will have to be followed at the end of the current road.

 This process allows the user to reassure himself on the indications to follow, without having to constantly look at his display. The use of steering wheel controls is particularly well suited for this type of system request, which can in particular take place in a complex driving or maneuvering situation (complex intersection, highly congested, not allowing visual consultation of the display) . In addition, this process is entirely consistent with the principle of non-intrusion by too many messages which would end up losing their effectiveness and their acceptance by the user. elsewhere the following: the user can configure the system so that he no longer says any message spontaneously; then only the messages on the display change and the user has the possibility at any time to request a voice indication from the system according to the methods described above.

 The journey on the main network therefore generally requires only as many advertisements as there are axes to be taken, which greatly limits the number of advertisements required and increases the user-friendliness of the system.

 Furthermore, the guidance method according to the invention comprises a method for choosing a route from among several possible on the main network, as a function of a certain number of parameters for updating the information on traffic conditions.

 Indeed, on the main network, the route can be broken down into a series of axes to be taken, these axes being described by their nomenclature. It is then possible to view the route in the form of a list of schedules, allowing the driver to view the route without displaying a map.

 On receipt of a road information message transmitted by radio or signaling, it is then possible to easily assess the interest of an alternative route in the event of difficulty on the calculated route. To do this, simply view the list of axes corresponding to the initially planned route, select the problem axis, declare it blocked in the guidance system, and request a new route calculation. The new route can in particular be presented in the form of a potential saving of time compared to the congested route, or in the form of the distance which it represents.

 This approach therefore allows traffic difficulties to be taken into account by the route calculator, and this can give an indication of the interest of an alternative route even before arriving in the vicinity of the difficulty.

 It will be understood that this approach is only valid for an occasional difficulty, such as an unforeseen traffic jam.

In the event of several difficulties, it is not possible to enter them all to request new route calculations.

 In all cases, the system constantly observes the position of the vehicle relative to the network and the calculated route and automatically proposes a new route as soon as the vehicle departs from this route.

 According to an advantageous embodiment of the invention, the two database levels are obtained by using two separate simplified databases: a first database containing the simplified information of the main road network, and a second database containing final destinations in simplified form.

 The first database or the first level allows the calculation of a route and the guiding of an initial node of the route calculated on this network, close to the starting point, towards an end node of the route on this network , close to the finish. The second database allows the programming of the destinations and the final guidance of the last node of the network towards the destination.

 According to the invention, the two databases are preferably simplified by the use of an absolute location module by satellites or by terrestrial beacons, not requiring additional cartographic data for the calculation of the positions, contrary to the technique registration on digital vectorized map, called mapmatching.

 Furthermore, the final guidance method is such that it allows the user to be guided even to a given destination in the form of an address on a particular street, despite the accuracy of the location module which is only 1 'order of a hundred meters.

 The advantage is that only the minimum information necessary for each stage is stored in the system (destination programming, route calculation, guidance on the simplified road network, and final guidance to the destination), all preserving the universality of the choice of possible destinations.

 In particular, the database of streets used for programming the destination can be stored in a compressed form. When used, the data in the desired area is temporarily decompressed into RAM. Then we can free this memory when the system carries out the actual guidance. In addition, since this street base is not used for actual guidance, it does not need to be organized in a network, but can simply be represented in the form of lists.

 We thus arrive at a simplified guidance service, less expensive but nevertheless effective.

 Referring now to Figure 5 showing a block diagram of a device capable of implementing the method according to the invention. This device 10 comprises a location module 11, a memory medium 12 containing databases, one or more control devices 13, 14 making it possible to program the destination, a device 15 for presenting guidance information to the user, a device 17 for sound reproduction of voice messages, and a calculation unit 16. All of these elements are already known in themselves, and will therefore not be the subject of a detailed description, only their particular characteristics being underlined.

 The location module 11 is in particular made up of an absolute radiolocation system, by satellites or by ground beacons, preferably coupled to dead reckoning sensors making it possible to maintain the position permanently, even in situations of temporary unavailability radiolocation information. This localization can be supplemented if necessary by a cartographic registration system, in a manner known per se.

 Such a location device 11 makes it possible to achieve positioning accuracy of the order of 100 meters, and a few degrees in heading.

 The memory medium 12 of the guiding device 10 is intended to contain the databases necessary for guiding, and can be in the advantageous form of an electronic card carrying a memory. Preferably, the method according to the invention makes it possible to use only a low capacity memory containing simplified databases, the software for controlling the system, and possibly a rewritable memory area making it possible to record information specific to each user: usual destinations, own journeys, etc.

 The control devices 13, 14 of the guidance device 10 make it possible to carry out the programming of the destination, the choice of the route calculation method (the most direct, by the major axes, or according to other criteria), or consulting services: parking, service station, garages, hospitals, administrative services, etc. These control devices may in particular consist of keys on the front face of a housing 13, but also of a remote control 14 under the steering wheel allowing ergonomic and safe use, and possibly an infrared remote control (not shown) allowing by example for a passenger to program a destination or to consult the services contained in the database.

 A device for presenting information to the driver is provided, in the form of a display 15, which may be limited to a monochrome matrix display of low resolution (240 x 64 pixels).

 The calculation unit 16 is connected to the other elements of the device 10 and makes it possible to manage the inputs / outputs, the programming of the device, the route calculation, the progression of the position of the vehicle relative to this route, the selection of the guidance indications "by compass" or "as the crow flies", that is to say according to a remaining distance and a heading to join the main network known in the database, by " directional signs "at intersections along the route on the road network, then again" by compass "or as the crow flies" to reach the final destination, in accordance with the guidance process according to the invention.

 We will now describe the use of the method and the guiding device according to the invention, in conjunction with the figures, and according to different structures of the database of the guiding device.

 It is first necessary to load a guidance database into the memory of the device 10. A reduced size database allowing the implementation of the solution uses a portion of database dedicated to programming the destination, a part of the database dedicated to data concerning the simplified road network, and part of the database dedicated to low-speed speech synthesis vocabulary.

 According to one embodiment of the destination programming database, this can for example consist of three types of data: "map" data, "site" data, and "address" data, such as shown schematically in Figure 4.

 The "map" data, inexpensive in memory, describe the grid 18 of the maps and city plans and connect this grid to the geographical references of the location module 11 (FIG. 5) via the coordinates of a particular point 19 of the covered area.

 The "site" data, fairly inexpensive in memory, are lists of sites linked to cities, each site being described by name, geographic coordinates, possibly multiple if the site has several entries, plus any practical information: opening hours, telephone number, etc.

 The "address" data, very expensive in memory when they are raw, are much less so in the solution according to the invention. Indeed, the data are simplified and they can be compressed, for example city by city. They contain the list of streets 20 (Figure 2), themselves broken down into sections 21 for which the following elements are invariant: direction of traffic, orientation, type of lane (dead end, pedestrian lane). The other information is the coordinates of the ends 22, 23 of the streets 20, or of the sections 21 if the street 20 is broken down into several sections 21, and the street numbers on each side.

 The reduced-size database used in the context of the invention also contains a database concerning the simplified road network of the main road axes described by alphanumeric attributes, making it possible to know the length of the axes, the supposed fluidity of the traffic on the axes, the names of the axes, the directional signals, as well as binary attributes making it possible to specify certain properties of the roads with respect to the guidance mode; crossroads at the intersections of these axes, called main crossroads, described by their coordinates, possibly by name; certain crossroads located along the road axes, called secondary crossroads, described by their kilometer point on the main axis which contains them, and their coordinates.

 The use of the guidance system provided with the database described above then comprises two main phases: the programming of the destination to be reached, and the navigation to this destination.

 We will now describe the use of the method and the guiding device according to the invention, in several hypotheses for defining the destination.

 In a first case, the destination is chosen from the list of addresses, decompressed for the city considered. According to one embodiment, the user programs the street number. In this case, it will be guided to this street number.

 According to another embodiment, less costly in the number of data to store, the user selects from a list of sections constituting the street, the one which contains its destination. In this case, the system guides to one end of the programmed section, then tells the user which course to take.

 In all cases, programming is done using one of the control means 13 and 14, the lists being presented on the display 15.

 When the destination is programmed, the system calculates a route by optimizing a criterion (distance, time, etc.), in the conventional way. For this purpose, the system uses the stored database. The typical route is made up of a list of nodes, the first of which is chosen near the starting point and the last of which is near the ending point. The system then guides the user to the first crossroads by permanently indicating to him on the display device 15 (FIG. 4) and by the speech synthesis device, where he is situated as the crow flies. The distance 26 and heading arrow 27 information to be followed is called "compass" guidance. This type of guidance is first done to the node of the main network closest to the vehicle, among those forming part of the route considered.

Then, upon arrival at the first crossroads, the system gives the user guidance instructions for taking the next route on the route which leaves from this crossroads, using the information from the existing directional signs, here called "panels". This goes on immediately to the last node 24 of the route, which is located close to destination 3 (FIG. 4). This completes the guidance phase on the main network. The display on the display device 15 of the device is shown in FIG. 6 for the initial guidance phases and on the network. At time 1, it is indicated that the vehicle is 800 meters as the crow flies from the first crossroad 2, towards which we are heading straight ahead (arrow 27). The final destination 3 is indicated at 5.1 km as the crow flies, going generally to the right (arrow 35). At time 2 corresponds the arrival on the D39 axis near the first crossroad 2, whose indication is maintained. At time 3, it is the exit of the crossroad 2 with momentary maintenance of the directional sign (D39 - Boulogne
Billancourt) and indication of the overall direction (arrow 34). The distance as the crow flies to destination 3 has increased to 4.4 km. At time 4, the vehicle is between two crossroads in the network. There is suppression of the indication of the directional sign, and there is more than to follow the road (D39) during 2,4 km until the next change of axis.

 Then, the system goes into the final guidance phase towards the destination 3. For this purpose, the system now indicates on the display device 15 and through the speech synthesis device, where the destination 3 is located in flight d bird, by the distance information 26 and the arrow 27 indicating the course to follow: it is the guidance with the compass towards the destination 3. A threshold of remaining distance to the destination can be provided, below which the display becomes even more precise. For example, in FIG. 4, the driver of the vehicle in position 28 in street A can see at 27 on display 15 that destination 3 is generally located on the left, in street B.

 Arriving near destination 3, the user searches for it in its immediate environment.

The identification of the destination 3 will advantageously be facilitated by a reminder on the screen 15 of information concerning the programmed destination (for example the orientation of the street relative to the vehicle).

 According to one embodiment, the device automatically offers the user a list of services close to the vehicle, when it approaches the destination, thus avoiding the tedious programming of a service almost always desired (for example a list four car parks with name, distance and heading information to reach them, one of which can be chosen as a new destination).

According to a complementary embodiment, the destination is chosen from a list of destinations, which can include agglomerations, sites or remarkable places to choose from a list of names. These destinations are identified by their coordinates in the destinations database, and possibly by other information offered to the user, such as an address,
The orientation of the street which gives on the entry of the destination, or a summary description.

 According to a variant illustrated in FIG. 3, a destination 19 can be programmed in the form of an address or a geographic location, instead of choosing a destination from a pre-established list.

 In this case of programming the destination, the solution consists in using the usual road maps and city maps 18. These are generally associated with a street index and provided with a regular grid making it possible to find on the maps the streets of the index. We then use a database containing the characteristics of the grid of road maps and city maps, then we locate the destination in relation to the grid of the chosen map (position and orientation of the street). The advantage is that this solution is easy to understand for the user, the cards used being the usual cards. In addition, the characterization of a map is very simple, adapts to any grid map and requires a very small database.

 The database of maps and city maps contains, for each map: the map references, the geographic coordinates of a reference point 19 which can be chosen as the bottom left corner of a reference box 29 of the grid, the characteristics of the grid defining the map coordinates, and the map coordinates of the reference box 29, and the orientation of the grid relative to the north.

 The use of the guide device is then as follows.

If the user knows the destination address (street name and possibly number):
a) it searches for the street in the street index 30 associated with the map used, where it reads the code corresponding to the coordinates of the street on the map;
b) it can then program the code in the system, using the input and display means of the device 10;
c) he can also refine the programming of destination 3. To do this, he can refer to the map to locate box 31 of the grid corresponding to the code, and thus identify his street B inside box 31. A programming cursor 33 can be moved to point to the relative position of the user's destination relative to box 31 on the map;
d) finally, the user can specify the course of the street as he sees it on the map viewed from above, by rotation of the orientation pointer 32 displayed on the display 15, and actuated by the through a means of inputting the device.

In another case where the user knows the geographic location of his destination:
- it locates the box of its destination by directly consulting the map, then it continues with steps b, c and d above.

 Other variants of programming the destination and guiding it are possible within the framework of the invention, depending on the content of the database used.

 Ultimately, the guiding device and method according to the invention make it possible to achieve the set goals, and ensure efficient, precise, and easy to use guiding towards a destination, while calling upon simpler and less material means. expensive than those already known.

Claims (20)

 1. A method of guiding a road vehicle, based on the determination of the instantaneous position of the vehicle, on the optimization of a route making it possible to reach a destination chosen from address lists and lists of street numbers , and on the indication in real time of guidance messages to follow in order to respect this route, characterized in that the route is optimized taking into account the tracks of the main network and taking into account the phases of movement on the network secondary with directions and distance as the crow flies from the starting point to a crossroads on the main network and from the main network to the destination.  2. Guidance method according to claim 1, characterized in that the guidance comprises a phase of guiding from the starting point to the main network, a phase of guiding on the main network, and a phase of guiding the main network to the destination. .  3. Guidance method according to claim 2, characterized in that in the guidance phase towards the main network, the guidance indicates the heading and the distance as the crow flies to a crossroads of the main network.  4. Guidance method according to any one of the preceding claims, characterized in that in the phase of guiding the network towards the final destination, the guidance indicates the course and the distance as the crow flies to the destination and, below a certain distance from the destination, the street heading of the destination.  5. Guidance method according to one of claims 1 to 3, characterized in that in the phase of guiding the network towards the final destination, the guidance indicates the heading and the distance as the crow flies to one end of a section constituting the street of the destination and, below a certain distance from this end, the heading of the section of the destination.  6. Guidance method according to one of the preceding claims, characterized in that the destination can be chosen from road maps or from a guide plan comprising a numbered grid.  7. Guidance method according to one of the preceding claims, characterized in that when approaching the destination, the system can offer guidance to a service, in particular a car park, chosen from a list of services determined automatically as being closest to the vehicle.  8. Guidance method according to any one of the preceding claims, characterized in that the guidance on the axes of the main network is based on directional signaling and road nomenclature at a plurality of complex crossroads placed at the intersections of these axes .  9. Guidance method according to any one of the preceding claims, characterized in that the guidance in complex crossroads uses two names of directions corresponding to the axis to be taken, the name or the nomenclature of this axis and where appropriate a indication of overall direction to take, expressed angularly with respect to the longitudinal axis of the vehicle, changing in real time with the movements of the vehicle, the direction names being chosen so that, while being valid at the level of the crossroads concerned, these directions respect the best continuity along the route.  10. Guidance method according to any one of the preceding claims, characterized in that the directional guidance at the level of complex crossroads is combined with non-intrusive guidance based on the indication of only changes of roads or road entities.  11. Guidance method according to any one of the preceding claims, characterized in that between two crossroads, the only guidance indication is the name or the road nomenclature of the current road, unless one of the directions indications still remains valid. at the second crossroads, in which case it can remain displayed.  12. Guidance method according to any one of the preceding claims, characterized in that the guidance indications at the level of the complex intersections where the arrival takes place on several lanes, are supplemented by preliminary announcements capable of ensuring correct positioning by report to these queues with reference, if necessary, to road works.  13. Guidance method according to any one of the preceding claims, characterized in that the user can at any time ask the system for voice guidance information, the nature of which may depend on the context, in particular the situation of the vehicle with respect to at the crossroads of the route.  14. Guidance method according to any one of the preceding claims, characterized in that the possible routes are displayed without displaying a map in the form of a list of road classifications representing the axes to be taken.  15. Guidance method according to any one of the preceding claims, characterized in that the user can himself declare that an axis is blocked, so that the system proposes an alternative route avoiding this axis.  16. Guidance method according to any one of the preceding claims, characterized in that the system constantly observes the position of the vehicle relative to the network and to the calculated route and automatically proposes a new route as soon as the vehicle departs of this route.  17. Road vehicle guiding device (10) for implementing a guiding method according to any one of the preceding claims, characterized in that it comprises, connected to a calculation unit (16), a localization module (11), a memory medium (12) containing guidance databases, one or more control devices (13, 14) for programming the destination, and a presentation device (15) guidance information to the user.  18. Guidance device (10) according to claim 17, characterized in that the guidance database comprises a first database corresponding to the main traffic lanes, based in particular on the traffic patterns, and a second base containing the lists of destinations, in particular the lists of addresses and the lists of services.  19. Guidance device (10) according to claim 18, characterized in that the databases of the network of main traffic lanes and of destination lists include simplified data, the database of destination lists being capable of high compression, the whole representing a small memory footprint.  20. Guide device according to any one of claims 17 to 19, characterized in that it can be entirely controlled from a control device under the steering wheel of the vehicle.