GB2551125A

GB2551125A - Method for operating a navigation system of a vehicle, as well as vehicle

Info

Publication number: GB2551125A
Application number: GB1609734.7A
Authority: GB
Inventors: Hill Andrew; Burr John
Original assignee: Daimler AG
Current assignee: Mercedes Benz Group AG
Priority date: 2016-06-03
Filing date: 2016-06-03
Publication date: 2017-12-13
Also published as: GB201609734D0; WO2017207100A1

Abstract

A method for operating a navigation system of a vehicle (car, ship, airplane) travelling along a first route, 85, from a starting location, S, to a destination, D. The method comprising determining a current location of the vehicle, showing by means of an electronic display (screen, monitor) in the vehicle, a virtual map, 30, with the current location of the vehicle. At least one second additional route (path, trail), 101, having the same starting location and destination as the initial route (but which is different from the first route) is determined. The virtual progress the vehicle would make as well as the location the vehicle would be at when using the second route instead of the first route is determined. Finally at least one second symbol, 34, indicative of the determined location the vehicle would currently be at when using the second route instead of the first route is shown on the electronic map. The at least one second symbols are ghost / phantom drivers.

Description

Method for Operating a Navigation System of a Vehicle, as well as a Vehicle

The invention relates to a method for operating a navigation system of a vehicle according to the preamble of patent claim 1, as well as a vehicle.

Such a method for operating a navigation system of a vehicle travelling along a first route from a starting location to a destination can be found in US 2010/0312466 A1. The method comprises a first step of determining a current location of the vehicle. The method further comprises a second step of, by means of an electronic display arranged in the interior of the vehicle, showing or presenting a virtual map of at least a portion of the surroundings of the vehicle. In a third step of the method, at least one symbol indicative of the current location of the vehicle is shown on the virtual map by means of the electronic display and on the basis of the determined current location. Thus, the driver of the vehicle can see the current location in relation to the surroundings by looking at the electronic display showing the virtual map and the symbol.

The method further comprises a fourth step of determining a second route having the same starting location and the same destination as the first route, wherein the second route is different from the first route.

Moreover, US 6 488 505 B1 shows a simulated vehicle system comprising a simulated vehicle configured to traverse a simulated course and a data structure holding a plurality of course finish times.

It is an object of the present invention to provide a method and a vehicle of the aforementioned kind so that a particularly advantageous operation of the vehicle can be realized.

This object is solved by a method having the features of patent claim 1 as well as a vehicle having the features of patent claim 7. Advantageous embodiments with expedient developments of the invention are indicated in the other patent claims.

The term “vehicle” describes all kinds of transportation systems which could benefit from a navigation system such as a road vehicle like a car, a watercraft like a ship or an air vehicle like a plane, a drone or a copter.

In order to further develop a method of the kind indicated in the preamble of patent claim 1 in such a way that a particularly advantageous operation of the vehicle can be realized, according to the present invention, the method comprises a fifth step of determining a virtual progress the vehicle would make when using the second route instead of the first route to travel from the starting location to the destination. This means, in the fifth step, an assumption is made on the progress the vehicle would make or would have made if the driver of the vehicle chose or had chosen the second route instead of the first route to travel from the starting location to the destination.

The method according to the present invention further comprises a sixth step of, on the basis of the determined virtual progress, determining a location the vehicle would currently be at when using the second route instead of the first route. Said location the vehicle would currently be at when using the second route instead of the first route is also referred to as a second location. Moreover, the method according to the present invention comprises a seventh step of, by means of the electronic display and on the basis of the determined virtual progress, showing or presenting, on the virtual map, at least one second symbol indicative of the second location. By showing both the first symbol and the second symbol, both the current location of the vehicle and the second location the vehicle would be at if the driver had chosen the second route instead of the first route are optically communicated to the driver. Thus, for example, the driver can see whether or not the first route is advantageous over the second route with regard to, for example, arriving earlier at the destination.

Users of navigation systems of vehicles may have limited trust in traffic-aware routing causing a loss of engagement in these navigation systems of the vehicles. By means of the method according to the present invention, respective performances of alternative routes can be shown to the driver of the vehicle, the driver being a user of the navigation system. Thus, the method according to the present invention will help to reinforce the efficacy of the navigation system. Specifically, the second symbol represents or can be seen as a ghost driver since the second symbol is indicative of said second location at which the vehicle is currently not but would have been or would be if the driver had chosen the second route instead of the first route. Hence, the said ghost driver can show on the virtual map and, thus, on the electronic display the hypothetical progress the vehicle and, thus, the driver would have made or would make if the driver had made a different routing decision in terms of choosing the second route instead of the first route.

By means of the method according to the present invention, the confidence of the driver in the navigation system is reinforced since, for example, the method according to the present invention can optically communicate to the driver that the first route calculated and provided by the navigation system is advantageous over the second route which, for example, could be taken by the driver. It should be noted that the navigation system can be native to the vehicle, considered an “on-board” navigation system, or present on a consumer electronic device and displayed either on the consumer electronic device or pushed to the on-board navigation system display of the vehicle via well-known connectivity methods. Moreover, since both symbols are shown on the virtual map, the first symbol and, thus, the vehicle and its driver may race or compete against said ghost driver so that the method according to the present invention comprises an aspect of gamification, thereby realizing additional engagement. The term “gamification” describes the application of game-design elements and game principles known from, for example, computer games in non-game contexts, wherein, in the present case, such a non-game context is guiding the driver from the starting location to the destination by means of a navigation system. By using an aspect of gamification - like comparing or evaluating achievements as described below - the user of the navigation system can experience fun or a competitive challenge while occupying himself with the progress of the vehicle. Thus the user is even more goal-oriented that the vehicle he is responsible for and will achieve the destination earlier or in a more efficient way.

In an advantageous embodiment of the invention, the method according to the present invention further comprises the additional step of comparing the current location of the vehicle with the second location the vehicle would be at if the driver had chosen the second route instead of the first route. The second location is the location of the ghost driver. For example an electronic control unit (ECU) - which could be implemented within the navigation system for instance - compares the current location with the second location by evaluating the progress (e. g. in miles, kilometers, hours or minutes) the vehicle and the ghost driver have made from the starting location or by evaluating the distance (e. g. in miles, kilometers, hours or minutes) to the destination or by evaluating the time at which the vehicle and the ghost driver arrive at the destination.

In a further advantageous embodiment of the invention, the method according to the present invention further comprises the additional step of determining a result of the comparison of the current location with the second location. By way of example the ECU determines if the vehicle or the ghost driver has made the most or fastest progress from the starting location or which of them is closer to the destination or which of them arrives earlier at the destination or with less fuel consumption for the route from the starting location to the destination. The rating can also be determined in a more sophisticated manner by determining the trip differences between the vehicle and a ghost, such as how much earlier the vehicle or the ghost driver arrived at the destination. Furthermore a rating score can be implemented by assigning trip parameters (fuel consumption, average speed, trip time, etc.) numerical values on a simple scale where aggregating these values can result in a total trip score. As an example, the score of the driver of a route taken can be compared with a score of the ghost driver of a different route or a score of another user.

In a particularly advantageous embodiment of the invention, the method according to the present invention further comprises the additional step of showing the result of the comparison of the current location with the second location, e.g. by means of the electronic display. This notification of the user can be dependent on a further condition like that the vehicle or the ghost driver arrives at the destination. Hereby a distraction of the user can be reduced.

The idea behind the present invention is that navigation, for example GPS-enabled navigation (GPS - Global Positioning System), has become standard in vehicles such as passenger vehicles, and increasingly this navigation takes into account current traffic conditions to provide an adaptive experience. The navigation system of the present invention should not be considered to be limited to GPS-enabled navigation but can be implemented with other GNSSs such as GLONASS or Galileo, or non-satellite localization systems. This adaptive experience is an adaptive routing which gives the user an optimal path to the destination, given current contextual information such as speed limits and/or current traffic situations, but it requires some trust from the user. Often users will not accept the route calculated and recommended by the navigation system of the vehicle but instead follow their own judgements, which they sometimes regret. This lack of faith in the adaptive navigation system of the vehicle detracts from the experience of the user in the vehicle. By showing the user, i.e. the driver of the vehicle, the progress they would have made or would make on the alternative second route, they can gain confidence in the navigation system which recommends the fastest route in the form of the first route. This allows for the creation of an ultimate navigation experience that provides not only the fastest route but also confidence in the navigation system.

In an advantageous embodiment of the invention, the virtual progress is determined on the basis of data indicative of a current traffic situation along the second route. Hence, the virtual progress and, thus, the second location can be determined particularly precisely. For example, the data indicative of the current traffic situation are provided by other vehicles and/or by providers, wherein said data are received by the navigation system of the vehicle.

Alternatively or additionally, for example, the virtual progress is determined on the basis of speed limits, in particular current speed limits, along the second route so that the second location and the virtual progress can be determined particularly precisely.

In a further advantageous embodiment of the invention, the virtual progress is determined on the basis of data indicative of an actual progress of at least one second vehicle travelling along at least a portion of the second route. Thus, the virtual progress and, thus, the second location can be determined very precisely since, for example, the actual progress of the second vehicle can be used as the virtual progress the first vehicle would make or would have made if the driver had chosen the second route.

In a particularly advantageous embodiment of the invention, the navigation system of the first vehicle receives data indicative of a current speed of the second vehicle. Thereby, for example, the navigation system can determine the second location on the basis of a speed at which the first vehicle could drive or travel along the second route if the driver had chosen to use the second route to get from the starting location to the destination.

Preferably, at least one optical signal indicative of this speed is shown by means of the electronic display. For example, said optical signal comprises a value of the speed of the second vehicle so that the driver of the first vehicle can compare the speed of the second vehicle with a current speed of their own vehicle.

In a further advantageous embodiment of the invention, the data are received directly from the second vehicle by the navigation system. For example, the data indicative of the actual progress of the second vehicle and/or the data indicative of the current speed of the second vehicle are received by car-to-car communication so that the data are directly received from the second vehicle by the navigation system.

Alternatively or additionally, the data are received from at least one intermediate electronic computing device such as a server being different from the first and second vehicles. By considering actual or current data for determining the virtual progress at the second location, wherein said data are indicative of a current state of movement and/or of a progress of at least one second vehicle travelling along the second route, a connectivity between the first and second vehicles is realized so that the virtual progress at the second location can be determined particularly precisely. Thereby, the vehicles can interact and exchange information about their respective progresses along the respective routes so that a particularly advantageous operation can be realized.

The invention also relates to a vehicle comprising a navigation system which is configured to perform a method according to the present invention. Advantages and advantageous embodiments of the method according to the present invention are to be regarded as advantages and advantageous embodiments of the vehicle according to the present invention and vice versa.

Further advantages, features, and details of the invention derive from the following description of a preferred embodiment as well as from the drawings. The features and feature combinations previously mentioned in the description as well as the features and feature combinations mentioned in the following description of the figures and/or shown in the figures alone can be employed not only in the respective indicated combination but also in any other combination or taken alone without leaving the scope of the invention.

The drawings show in:

Fig. 1 a schematic view of a virtual map shown on an electronic display of a vehicle in a method for operating a navigation system of the vehicle;

Fig. 2 a further schematic view of the virtual map;

Fig. 3 a further schematic view of the virtual map;

Fig. 4 a further schematic view of the virtual map;

Fig. 5 a further schematic view of the virtual map;

Fig. 6 a further schematic view of the virtual map; and

Fig. 7 a schematic and sectional side view of the vehicle performing the method.

In the figures the same elements or elements having the same functions are indicated by the same reference signs.

In the following, a method for operating a navigation system 10 (Fig. 7) of a vehicle 12 will be described on the basis of Figs. 1 to 7. As will be described in greater detail below, the vehicle 12 travels along a first route 14 (Fig. 2) from a starting location S to a destination D. For example, the navigation system 10 provides that a current location of the vehicle 12 on earth can be determined by means of the navigation system 10 using signals provided by, for example, satellites.

As can be seen from Fig. 7, the navigation system 10 comprises at least one electronic display 16 arranged in the interior 18 of the vehicle 12. The navigation system 10 used in the vehicle 12 can be considered native i.e. built into the vehicle, or from a consumer electronic device (not shown) where the navigational map output and the method of the present invention can be pushed to the at least one electronic display 16 from the consumer electronic device using known connectivity methods. Moreover, Fig. 7 shows further vehicles 20 and 22 travelling further routes 24 and 26 which are different from the first route 14. However, the routes 24 and 26 have the same starting location S and the same destination D as the first route 14. For example, the vehicle 20 travels along the route 24, wherein the vehicle 22 travels along the route 26. Moreover, the driver 28 of the vehicle 12 can be seen in Fig. 7, the driver 28 sitting in the interior 18.

For example, the navigation system 10 uses adaptive navigation to guide or route the vehicle 12 from the starting location S to the destination D. This means, for example, the navigation system 10 uses adaptive navigation to calculate and provide the different routes 14, 24 and 26. The main purpose of adaptive navigation is to provide the fastest route from the starting location S to the destination D based on, for example, current traffic conditions, rather than historical or theoretical traffic conditions. Although this gives perfect information about the current state of traffic, it still makes no guarantees about how the traffic will proceed. This uncertainty can lead to a lack of faith in the navigation system 10 of the vehicle 12, and a nagging question about how much better or worse a different route would be. Sometimes, this leads the driver 28 to take a different route than what is suggested or recommended by the navigation system 10, which can cause even more frustration when the different or alternative route selected by the driver 28 is also found to be poor. Since the driver 28 uses the vehicle 12 and, thus, the navigation system 10, the driver 28 is a user of the navigation system 10. However, adaptive navigation has the potential to not only optimize traffic routes for users of said adaptive navigation, but also for all drivers in the local area, due to the natural balancing effect of distributing some of the drivers away from heavily congested areas.

As will be described in greater detail below, the said method also incorporates an aspect of gamification. Gamification is a technique used to take a task that might otherwise be considered a chore and provides additional entertainment value. This can be used to increase engagement or promote certain behavior. For example, in the context of gamification, an electronic display in the interior 18 shows the amount of fuel a hybrid system of the vehicle 10 is saving over using an internal combustion engine only, thereby reassuring the user of the value of their purchase in the form of the hybrid system. Such a comparison system can also save historical performance data and result in the user competing against themselves to save a record amount of fuel by driving more economically. As another example, aftermarket devices allow driving dynamics to be uploaded to a server so that driving behaviors can be compared among different users, fostering a friendly competition about driving efficiency.

The method comprises the following steps: determining a current location of the vehicle 12; showing, by means of the electronic display 16, a virtual map 30 (Fig. 1) of at least a portion of the surroundings 31 of the vehicle 12; by means of the electronic display 16 and on the basis of the determined current location: showing, on the virtual map 30, at least one symbol 32 (Fig. 3) indicative of the current location of the vehicle 12; -determining at least one second route 24, 26 having the same starting location S and the determining a virtual progress the vehicle 12 would make when using the second route 24 or 26 instead of the first route 14 to travel from the starting location S to the destination D; on the basis of the determined virtual progress: determining a location the vehicle 12 would currently be at when using the second route 24, 26 instead of the first route 14; and by means of the electronic display 16 and on the basis of the determined virtual progress: showing, on the virtual map 30, at least one second symbol 34, 36 (Figs. 3 and 4) indicative of the determined location the vehicle 12 would currently be at when using the second route 24, 26 instead of the first route 14.

As another example the method additionally comprises the following step: - by means of the navigation system 10 and on the basis of the determined current location and a user inputted or automatically selected destination D: determining a first route 14 between the current location of the vehicle 12 noted as a starting location S and the destination D;

In the embodiment described on the basis of Figs. 1 to 7, a key component of the method is a crowd sourced adaptive navigation system, wherein expected progress as a function of time can be estimated along the possible routes 14, 24 and 26 at the start of the trip, then updated and refined as time elapses, but this alone does not consider other users of the said system in the crowd travelling similar routes. Instead of only observing changes in overall traffic conditions and updating estimated progress based on this information, the method or system can observe the actual progress of other vehicle drivers on similar routes to provide more accurate ghost cars and more compelling gamification. As will be described in the following, the progresses of the vehicles 20 and/or 22 along the routes 24 and 26 are considered for determining the virtual progress of the vehicle 12. The navigation system and, thus, said method not only tracks the route of the driver’s 28 current position to the destination D, but also from the starting location S to several other points along various routes to the same destination D. At the beginning of the trip, these locations are all the same, namely the origin or the starting location S of the trip. As the driver 28 begins driving, said ghost cars are updated to be places the driver 28 or the vehicle 12 could have been or could be at that time, based on a combination of overall traffic conditions and real users of the system travelling in the same area, wherein said real users are the respective drivers of the vehicles 20 and 22.

The virtual map 30 shown in Fig. 1 shows or illustrates an area in which the driver 28 wishes to navigate between the starting location S and the destination D. For example, the starting location S is the office of the driver 28, wherein the destination D is their home. In the said area, there are several highways 17, 85, 101 and 280 the driver 28 could take, any of which could be optimal given a particular traffic situation.

For example, the navigation system 10 receives at least one input from the driver 28, wherein the driver 28 enters at least the destination D by means of said input. Further, the navigation system 10 by way of a transmission signal receives the current location of vehicle 12 and can automatically use this current location as the navigational input for the starting location S of the vehicle 12 and thereby the driver 28. Alternatively, the driver 28 can also enter their current location as the starting location S from which the driver 28 wishes to travel to the destination D. When starting the navigation, several routes 14, 24 and 26 are calculated and offered by the navigation system 10, wherein the calculated and offered or provided routes 14, 24 and 26 are shown on the virtual map 30 as shown in Fig. 2. The driver 28 selects one of these routes 14, 24 and 26 and begins driving. For example, after five minutes, the driver 28 has made some progress towards the destination D, and information from traffic services can determine how much progress the driver would have made along a different route as shown in Fig. 3. In Fig. 3, the symbol 32 illustrates the vehicle 12, in particular the current position of the vehicle 12 travelling along the route 14. In particular, the symbol 32 indicates the driver’s 28 selected route 14 along highway 85. The symbol 34 represents a navigational ghost, showing how much progress the driver 28 and, thus, the vehicle 12 would have made if the driver 28 had selected highway 101 to travel along. This means the symbol 34 illustrates the said virtual progress the driver 28 and the vehicle 12 would make when using the second route 24 instead of the first route 14.

For example, after ten minutes, the driver 28 and the vehicle 12 come to a junction 38. At the junction 38, the driver 28 must or can decide whether to stay on highway 85 or switch to highway 280. There is a potential that users of adaptive navigation systems -especially those users who do not trust such systems - can ignore the suggested routes, i.e. the routes recommended by the navigation systems. Due to traffic, either could be optimal, but depending on the driver’s trust in the navigation system 10, they might make either choice.

In the present example, the driver 28 chooses to switch to highway 280 as shown in Fig. 4 instead of staying on highway 85 and travelling along the route 26. Said navigational ghost represented by the symbol 34 is also referred to as a ghost or ghost driver. With respect to Fig. 4 and in comparison with Fig. 3, the ghost represented by the symbol 34 has made some progress along highway 101, and a new ghost represented by the symbol 36 has been created, the ghost represented by the symbol 36 tracking progress along highway 85. This means the symbol 36 illustrates a progress the driver 28 would make or would have made when choosing highway 85, i.e. the route 26.

After fifteen minutes, the driver 28 turns from highway 280 to highway 17 towards the destination D as shown in Fig. 5. By means of the virtual map 30 and the symbols 32, 34 and 36 shown on the virtual map, the driver 28 can see that they have performed much better than the ghost represented by the symbol 34, the ghost represented by the symbol 34 being strictly behind the driver 28 and the vehicle 12. Moreover, the driver 28 can see that the ghost represented by the symbol 36 has become stuck in traffic on highway 85 and will probably arrive after the driver 28. In this situation, the driver 28 can gain confidence in their navigational choice, and enjoy a gamification component of the route since the driver 28 can race or compete against the said ghosts.

In the following, methods for creating said ghosts are described. Determining the respective ghost, in particular the respective position of the respective ghost which is also referred to as a ghost car, can be done in several methods. The most naive method is to take the average speed of a road segment at time intervals, and move the ghosts along with the average speed for each segment. This will work in all regions where traffic or navigation data is available. A more exciting method is to base the ghost on other drivers in the area such as the drivers of the vehicles 20 and 22.

Existing navigational services allow users to see each other, in particular to communicate with each other in such a way that the users or drivers of different vehicles can exchange information. In particular, profile information can be shared as well. If there is sufficient density of drivers, the drivers, in particular their vehicles such as the vehicles 12, 20 and 22, can be connected together as friendly adversaries. For instance, in the aforementioned example shown in Fig. 2, the ghost represented by the symbol 34 is created on the vehicle 20 which travels along highway 101 as shown in Fig. 6. In particular, the vehicle 20 driving along highway 101 at the same time the driver 28 decides to get onto highway 85 is discovered or detected. For example, the ghost represented by the symbol 34 can denote the driver of the vehicle 20 and track their progress in real-time, which will take the place of the road-segment average posted speed data. This could potentially be more up-to-date because it does not rely on speed averaging or on the navigation supplier.

For example, the navigation system 10 receives data indicative of respective progresses or a progress of the vehicle 20 travelling along highway 101. Thus, the position of the ghost represented by the symbol 34 is determined on the basis of the received data, which are, for example, broadcasted by the vehicle 20 travelling along highway 101. As can be seen from Fig. 7, said data are broadcasted by the vehicle 20 and received by the vehicle 12, in particular the navigation system 10, by means of a wireless data communication or connection 42. As shown in Fig. 6, some additional information about the driver of the vehicle 20 can be provided, such as the current speed and some profile information 40 of the driver of the vehicle 20.

For example, said profile information 40 can comprise a picture or an avatar of the driver of the vehicle 20. Of course, it is unlikely that the driver of the vehicle 20 will follow the exact proposed route 24 the whole time: For example, when the driver of the vehicle 20 or the vehicle 20 itself crosses highway 17, the ghost will depart from the driver of the vehicle 20 and the vehicle 20 itself, and fall back to road segment calculation until such time as another driver crosses its route, at which point the ghost represented by the symbol 34 can now denote the other driver.

List of reference signs 10 navigation system 12 vehicle 14 route 16 electronic display 17 highway 18 interior 20 vehicle 22 vehicle 24 route 26 route 28 driver 30 virtual map 32 symbol 34 symbol 36 symbol 38 junction 40 profile information 42 wireless data connection 85 highway 101 highway 280 highway D destination S starting location

Claims

1. A method for operating a navigation system (10) of a vehicle (12) travelling along a first route (14) from a starting location (S) to a destination (D), the method comprising: - determining a current location of the vehicle (12); - showing, by means of an electronic display (16) arranged in the interior (18) of the vehicle (12), a virtual map (30) of at least a portion of the surroundings (31) of the vehicle (12); - by means of the electronic display (16) and on the basis of the determined current location: showing, on the virtual map (30), at least one symbol (32) indicative of the current location of the vehicle (12); and - determining at least one second route (24) having the same starting location (S) and the same destination (D) as the first route, the second route (24) being different from the first route (14); characterized by the steps of: - determining a virtual progress the vehicle (12) would make when using the second route (24) instead of the first route (14) to travel from the starting location (S) to the destination (D); - on the basis of the determined virtual progress: determining a location the vehicle (12) would currently be at when using the second route (24) instead of the first route (14); and - by means of the electronic display (16) and on the basis of the determined virtual progress: showing, on the virtual map (30), at least one second symbol (34) indicative of the determined location the vehicle (12) would currently be at when using the second route (24) instead of the first route (14).

2. The method according to claim 1, characterized in that the virtual progress is determined on the basis of data indicative of a current traffic situation along the second route (24).

3. The method according to claim 1 or 2, characterized in that the virtual progress is determined on the basis of data indicative of an actual progress of at least one second vehicle (20) travelling along at least a portion of the second route (24).

4. The method according to claim 3, characterized in that the navigation system (10) receives data indicative of a current speed of the second vehicle (20), wherein, by means of the electronic display (16), at least one optical signal indicative of the speed is shown.

5. The method according to claim 3 or 4, characterized in that the data are received directly from the second vehicle (20) by the navigation system (10).

6. The method according to any one of claims 3 to 5, characterized in that the data are received from at least one intermediate electronic computing device being different from the vehicles (12, 20).

7. The method according to any one of claims 1 to 6, characterized in the additional step of: comparing the current location of the vehicle (12) with the location the vehicle (12) would currently be at when using the second route (24) instead of the first route (14).

8. The method according to claim 7, characterized in the additional step of: determining a result of the comparison of the current location of the vehicle (12) with the location the vehicle (12) would currently be at when using the second route (24) instead of the first route (14).

9. The method according to claim 8, characterized in the additional step of: showing the result of the comparison of the current location of the vehicle (12) with the location the vehicle (12) would currently be at when using the second route (24) instead of the first route (14).

10. A vehicle (12) comprising a navigation system (10) configured to perform a method according to any one of the preceding claims.