A TERRESTRIAL NAVIGATION SYSTEM AND METHOD Fleld of the InventionThe present invention relates to terrestrial navigation systems and methods, and more particularly to terrestrial navigation systems and methods used to indicate the relative direction of a destination from the navigation system.
Description of the Pnor ArtIn recent years, terrestrial navigation systems have been developed with the aim of replacing conventional paper maps. Much of the development has been concentrated on vehicle navigation systems aimed at removing the requirement for the driver to reference a paper map in order to determine the route to be taken to arrive at a particular destination.
Typically, such vehicle navigation systems store a digital map of the road networks in a storage device such as a CDROM or other suitable storage medium, and then aim to provide the user with a visual indication of the position of that user's vehicle on the map. When considering how to determine the current location of a vehicle, there are several choices. One possibility is to use a radio location method, such as Loran, which is typically accurate to within 100 to 3000 metres. An alternative approach is to use satellite systems to locate the vehicle. A well-known satellite system is the global positioning satellite system, or GPS. The GPS system includes a number of satellites in orbit which continuously transmit very precise timed radio signals. A GPS receiver within a vehicle navigation system will receive these radio signals from several satellites and will use these signals to calculate the distance from each satellite to the receiver, and in this way the position of the receiver can be calculated. The accuracy of the GPS system is quite good, being of the order of 10 to 50 metres, but it is still insufficient by itself to determine the position of a vehicle on a road stored within the digital map of the vehicle navigation system.
Hence, in the known terrestrial navigation systems, positioning systems such as Loran and GPS are used as an absolute calibration input, but other processes, such as "dead reckoning" and "map matching" are used to maintain an accurate tracking of the vehicle's position. These techniques are described in the article entitled "A Modular Approach to the Design of an In-Vehicle Advanced Traveller InformationSystem", by Allan Kirson, Motorola Incorporated, published in Automotive DesignEngineering, Century Press, 1992, Book 5756 R3, pages 295-298. Dead reckoning is the process of calculating a current location based on a previous location, how far the vehicle has travelled, and in what direction. Wheel speed sensors on the nondriving wheels, and a direction sensor, such as an electronic compass, are often used to provide the distance travelled, the speed, and the heading inputs used for dead reckoning calculations. However, dead reckoning is prone to incremental errors due to roadway contours, uneven tyre pressure, wheel slip, etc, and since it is relative in nature, cannot be relied upon by itself to provide accurate positioning.
Hence, a technique called "map matching" is used in addition to dead reckoning. The digital map stored in the storage medium of typical prior art vehicle navigation systems contains detailed information required for route guidance, such as traffic signs, tum restrictions, and one-way restrictions, as well as the topological data required for vehicle location detection. The digital map may be used as another input to determine the location by assuming that the vehicle is travelling on a road, and correcting the dead reckoning calculations accordingly.
From the above discussions, it will be appreciated that current vehicle navigation systems are very complex, since a large amount of storage is required to store the map data, and significant processing power is required to enable techniques such as dead reckoning and map matching to be performed.
Examples of such vehicle navigation systems are described in the articles "CARIN - A Car Information and Navigation System" by MLG Thoone, Philips, and "The Honda Navigation System" by the Honda Motor Company Limited, published at pages 315-325 and 291-292, respectively, of Automotive Design Engineering,Century Press, 1992, Book 5756 R3. Both of the systems described in these articles involve the storing of a detailed digital map, and the use of complex analytical techniques to determine the vehicle's position on those maps.
In summary, the known terrestrial navigation systems use techniques such asGPS for calibration or verification, and then employ vehicle sensors and complex processing techniques to continuously determine distance and heading travelled. To convert the vehicle's position into meaningful information for the driver, current navigation systems employ road or street map data and visually display the vehicle's position on the road or street map, or simplified graphical representation of the road network. In order to use the navigation system to best effect, the system requires digitised information of the physical road network in question, and the driver also needs to interpret the information through the road map displayed on the vehicle's navigation system display screen. This requires both a considerable amount of road data, thereby adding cost of a system, and additionally requires the attention of the driver, thereby adding to the risk of being distracted from the task of driving in a safe manner.
The problem of driver distraction can be alleviated somewhat by utilising a synthesised speech system, which uses a complex set of inputs from the required route, map data and current vehicle position to provide instructions to the driver, without requiring the driver to look at the map display. The use of such speech synthesis is discussed in the above mentioned article entitled "CARIN - A CarInformation and Navigation System". By using voice synthesis, the risk of unsafe driving practice is alleviated, but it is complex and expensive and still requires the need for a large amount of digitised road network data, and for complex processing techniques in order to place the vehicle's position on those digitised road networks.
The above description illustrates that, in an attempt to replace conventional paper maps, terrestrial navigation systems have become very complex, employing complicated techniques to determine the user's position on digital maps. The above discussion has concentrated on vehicle navigation systems since this is where much of the development has taken place, but the general problems discussed are applicable to any terrestrial navigation system, whether intended for use in a vehicle or otherwise.
Hence, it is an object of the present invention to provide a terrestrial navigation system which avoids the complexity of the known navigation systems.
Summanr of the InventionAccordingly, the present invention provides a terrestrial navigation system for indicating the relative direction of a destination from the navigation system, the system comprising: an input device for enabling a user of the system to enter an address identification for the destination; an address converter for determining terrestrial coordinate data corresponding to the address identification of the destination, the terrestrial coordinate data specifying a position on the earth's surface; a receiver for receiving signals specifying terrestrial coordinate data corresponding to the position of the navigation system on the earth's surface; and output means for providing an indication of the relative direction of the destination from the navigation system, the relative direction being derived from the terrestrial coordinate data of the destination and the navigation system.
By using a system in accordance with the present invention, there is no need to store a map of the road network, and additionally the system does not require complex processing techniques such as dead reckoning and map matching to be performed. In accordance with the present invention, an address converter is provided to determine, based on the address identification entered by a user, terrestrial coordinate data specifying the position of a destination'on the earth's surface. By this approach, the user may enter an address, or some form of encoded terrestrial coordinate data, and this can be converted directly to terrestrial coordinate data, such as longitude and latitude information, or a grid reference. The navigation system in accordance with the present invention then merely compares that terrestrial coordinate data with the terrestrial coordinate data corresponding to the position of the navigation system, as deduced by known positioning systems such as GPS, in order to provide an indication of the relative direction of the destination from the navigation system.
This indication may take the form of a visual display, on which both the destination and the current position are indicated, for example by symbols on a screen.
Alternatively, the indication may be provided orally via a speaker, such as by issuing a message, for example "destination at 3 o'clock". Since the user is not presented with a map of the road network, there is no need to perform complex calculations in order to determine the exact position of the vehicle on the road network, and hence a system in accordance with the present invention does not require a large storage capacity and further does not require the significant processing power of prior art systems.
In one preferred embodiment of the present invention, the address converter is arranged to access a database associating address identifications with terrestrial coordinate data specifying points on the earth's surface, and to retrieve the terrestrial coordinate data corresponding to the address identification of the destination.
The database may be stored on any suitable storage medium, and take any suitable form, provided that an address identification input can be correlated with corresponding terrestrial coordinate data stored in the database. In one embodiment, the database is a look-up table provided within the navigation system, this look-up table associating address identifications with terrestrial coordinate data. However, alternatively, the database may be provided as a remote database accessed by the address converter via a wireless link.
Preferably, in the above-mentioned preferred embodiment, the address identifications stored in the database are postal reference codes, and the user enters a postal reference code for the destination. It will be apparent to those skilled in the art that a database can readily be constructed that associates postal reference codes, such as the UK "postcodes", with terrestrial coordinate data, such as longitude and latitude information or a grid reference. Indeed, a number of such databases have already been produced, to provide Ordnance Survey grid references for the centroids of postcode boundaries. Such databases can be used for postcode labelling, address location, for survey purposes, and by parties that require a quick indication of a building's location, without requiring the complete address. For instance, such databases are used by a number of insurance companies in order to assess the risk of a property to be insured based purely on information about the postcode of that property.
In a second embodiment, the address converter is not arranged to access a database. Instead, the address identification takes the form of encoded terrestrial coordinate data, and the address converter is a decoder for decoding the encoded terrestrial coordinate data in order to determine the terrestrial coordinate data corresponding to the address identification.
In this embodiment, the encoded terrestrial coordinate data will typically be obtained by the user from a service provider, which may operate an automated service for providing encoded terrestrial coordinate data. For example, the user may contact the service provider by telephone before starting his/her joumey, and will be requested to specify the address identification for the desired destination. As with the previous embodiments, this address identification may take the form of a postal reference code, and may be input by voice or by pressing keys on the user's telephone.
The address data input by the user can then be compared with a database associating addresses with encoded terrestrial coordinate data, eg in the form of an encrypted code. Then the user can be provided over the telephone with the encrypted code corresponding to the address information supplied. Once the code has been received, the user can enter this code in to the navigation system as the address identification. In this embodiment, the address converter within the navigation system would take the form of a decoder arranged to determine the terrestrial coordinate data from the encrypted code entered by the user.
In one preferred embodiment of the present invention, the receiver of the terrestrial navigation system is a positioning system, which determines the terrestrial coordinate data of the navigation system by processing signals received from base stations. In such an arrangement, the terrestrial coordinate data of the destination determined by the address converter may be passed to the positioning system, and the output means is provided within the positioning system to provide the indication of the relative direction of the destination from the navigation system. By such an approach, the terrestrial navigation system may include a standard positioning system, such as a GPS, and may use the output device provided by that positioning system in order to provide the indication of the relative direction of the destination from the navigation system.
In an alternative embodiment, the receiver of the navigation system may be connected to a nearby positioning system, such as a positioning system located within the same vehicle, the terrestrial coordinate data of the positioning system being determined by processing signals received by the positioning system from base stations, and the receiver being arranged to receive the determined terrestrial coordinate data from the positioning system.
In such an arrangement, the navigation system preferably further comprises a processor arranged to process the terrestrial coordinate data received by the receiver and the terrestrial coordinate data determined by the address converter, and to produce an output signal used by the output means to provide said indication of the relative direction of the destination from the navigation system. In such an arrangement, the navigation system is arranged to receive an input from a positioning system, such as a GPS, and to then perform the necessary processing in order to provide an indication of the relative direction of the destination from the navigation system.
Preferably, the base stations generating signals which are processed by the positioning system, are satellites, and the positioning system in preferred embodiments is a global positioning system (GPS). However, it will be appreciated by those skilled in the art that the base stations need not be satellites and could, for example, be radio beacons, in which case the positioning system can be any appropriate positioning system that uses signals from radio beacons.
In preferred embodiments, the output means is arranged to be responsive to a command entered by the user to provide the indication of the relative direction of the destination from the navigation system. Hence, in preferred embodiments, the output means does not necessarily provide a continuous output of the relative direction of the destination from the navigation system. Rather, this output can be provided as requested by the user, for example when the user is approaching a junction, and hence needs to make a decision concerning the route to be taken. Thus, for example, if the user is approaching a Junction, and enters a command, for example via the input device, indicating that he/she requires an indication of the relative direction of the destination from the navigation system, then the output means can be arranged to provide that output, for example by displaying on a display screen symbols indicating both the destination and the current position, or instead by issuing a voice signal via a speaker to indicate the relative direction.
As mentioned earlier, the output means may be arranged to provide a display signal to a display device to cause a visual identifier for the destination and the visual identifier for the navigation system to be displayed on that display device, whereby the user is provided with an indication of the relative direction of the destination from the navigation system. Alternatively, the output means may provide a sound signal to a speaker to generate a voice identifying the relative direction of the destination from the navigation system. Indeed, any other suitable mechanism for providing that indication as an output may be used.
In preferred embodiments, the terrestrial coordinate data of the destination and the navigation system are used to derive relative distance information between the destination and the navigation system, and the output means is further arranged to provide an indication of the relative distance of the destination from the navigation system. It will be appreciated that if the terrestrial coordinate data relates to latitude or longitude information, or to a grid reference, then only a relatively simple calculation needs to be performed to calculate the straight line distance between the destination and the current location. This straight line distance information can be output at the same time as providing the indication of the relative direction, in order to provide the user with some information as to how far he/she is from the destination.
Viewed from a second aspect, the present invention provides a method of providing an indication of the relative direction of a destination from a navigation system, the method comprising the steps of: (a) receiving an address identification for the destination; (b) determining terrestrial coordinate data corresponding to the address identification of the destination, the terrestrial coordinate data specifying a position on the earth's surface; (c) receiving information specifying terrestrial coordinate data corresponding to the position of the navigation system on the earth's surface; and (d) providing an indication of the relative direction of the destination from the navigation system, the relative direction being derived from the terrestrial coordinate data of the destination and the navigation system.
Brief Descnption of the DrawingsThe present invention will be described further, by way of example only, with reference to preferred embodiments thereof as illustrated in the accompanying drawings, in which:Figure 1 is a block diagram illustrating a system in accordance with preferred embodiments of the present invention;Figure 2 is a flow diagram illustrating the processing steps performed in accordance with a first embodiment of the present invention;Figure 3 is a flow diagram illustrating the processing steps performed in accordance with a second embodiment of the present invention; andFigures 4A and 4B illustrate possible ways in which the destination and the current position may be displayed to a user of a system in accordance with preferred embodiments of the present invention.
Description of Preferred Embodlments A system in accordance with preferred embodiments of the present invention will be discussed with reference to Figure 1, which is a block diagram showing the features of a terrestrial navigation system in accordance with preferred embodiments.
For the purpose of describing a preferred embodiment, we will assume that the current position of the navigation system is provided by a GPS receiver, but, as discussed earlier, there is no requirement to use GPS, and any other positioning system, such asLoran which uses a radio location method, may be used.
With reference to Figure 1, a user of the navigation system 10 is able to input address information via the key input device 110, and this address information is received by the input interface 20 within the navigation system 10. In a first embodiment of the present invention, the address information entered takes the form of a postal reference code. For example, in the United Kingdom, the address information entered by the user would be a UK Postcode, a postcode being constructed of several parts, each defining in more detail the geographic area in question.
The UK postcode system works in the following manner. The first part of the code defines the postcode area, e.g. SO for the Southampton postcode area. There are over 120 postcode areas in the UK. The next part of the code denotes the postcode district, e.g. district 1 in the Southampton postcode area is denoted as SO1. There are over 2,700 postcode districts in the UK. The next part of the postcode denotes the sector, e.g. sector 3 in district 1 of the Southampton postcode area is denoted SO1 3.
There are over 9,000 postcode sectors in the UK. The final part of the UK postcode system uses a two letter combination to identify individual groups of addresses in the same street to within six to fifteen individual households/buildings/dwellings. An example may be SO1 3AB. In the UK, there are over 1.6 million unique postcodes.
In other countries, such as much of continental Europe and the United States of America, a five or six digit number forms the postal reference code, often referred to as a ZIP code, and act in a similar manner to the UK system, in determining an address to usually within a few buildings.
The address information received by the navigation system at the input interface 20 is passed via the processor 30 to an address converter 40. In the first embodiment, the address converter is arranged to access a database 50, associating address identifiers, in preferred embodiments postcodes, with terrestrial coordinate data specifying points on the earth's surface. As mentioned earlier, a number of databases that relate address information, such as postcodes, with terrestrial coordinate data, such as latitude and longitude or a grid reference, are being made available. The terrestrial coordinate data associated with a particular postcode is commonly the latitude and longitude or grid reference that corresponds to the centroid (centre of area) of the postcode. These databases are used for postcode labelling, address location, for survey purposes, and by parties that require a quick indication of a building's location, without requiring the complete address. For example, such databases may be used by insurance companies and other service providers to determine the exact location of a caller's property based on the postcode of that property provided by the caller. For insurance companies, the location can be used to assess the risk of insuring the property.
The exact location of the database is not important for the purposes of the present invention. Hence, the database may be provided locally, for example on aCDROM or internal ROM, as part of the navigation system, or alternatively may be provided at a central location and accessed by the address converter via a wireless link. Wherever the database 50 is located, the result of the address converter 40 accessing that database 50 is that the address converter will retrieve the terrestrial coordinate data corresponding to the postcode specified by the user.
In an alternative embodiment, the user may actually reference a service provider in order to obtain encoded terrestrial coordinate data corresponding to the address identification. Typically, the service provider may operate an automated service for providing encoded terrestrial coordinate data. For example, the user may contact the service provider by telephone before starting his/her journey, and will be requested to specify the address identification for the desired destination. This address identification could take the form of a postal reference code, and may be input by voice or by pressing keys on the user's telephone.
The address data input by the user can then be compared with a database associating addresses with encoded terrestrial coordinate data, eg in the form of an encrypted code. Then the user can be provided over the telephone with the encrypted code corresponding to the address information supplied. Once the code has been received, the user can enter this code in to the navigation system as the address identification. In this embodiment, the navigation system need no longer access the database itself, and instead the address converter within the navigation system would take the form of a decoder arranged to determine the terrestrial coordinate data from the encrypted code entered by the user.
By using encoded terrestrial coordinate data, the service provider could ensure that the data was only used in connection with a navigation system that had an appropriate decoder installed therein. In accordance with this approach, a database would not need to be stored within the navigation system, and a standard navigation system, such as a GPS unit, could readily be modified to include a decoding chip to convert the encoded data in to meaningful terrestrial coordinate data for the destination. The service provider could charge for the service by charging a fixed fee for each access to the service, eg. each telephone call by the user, or in any other appropriate manner.
In preferred embodiments, the navigation system 10 is connected to a GPS receiver 60, which intermittently receives signals from satellites 120 which enable theGPS receiver 60 to determine its position on the earth's surface in terms of terrestrial coordinate data such as longitude and latitude. The GPS receiver may be provided as an integral part of the navigation system 10, or alternatively the navigation system 10 can be connected to a standard GPS receiver 60 via a GPS interface 70, as illustrated in Figure 1.
In one preferred embodiment of the present invention, the processor 30 within the navigation system 10 is arranged to receive the terrestrial coordinate data of the destination via the address converter 40, and the terrestrial coordinate data determined by the GPS receiver 60 via the GPS interface 70. Hence, the processor 30 will be provided with both the terrestrial coordinate data of the destination and the terrestrial coordinate data of the GPS receiver 60. The terrestrial coordinate data of the GPS receiver can be taken as the terrestrial coordinate data of the navigation system, assuming the GPS receiver is nearby to the navigation system, such as being located within the same vehicle.
The processor 30 can then use both sets of terrestrial coordinate data to generate an output signal indicating the relative direction of the destination from the navigation system, this output signal being passed to the output interface 80 for sending in an appropriate format to an output device. In preferred embodiments the output device may be a display device 90 or a speaker 100. If the output device is display device 90, then the output interface 80 will preferably send the display device a signal that will cause the display device to display two symbols on the display screen, one representing the location of the destination, and one indicating the relative location of the navigation system. In addition, a history of points showing previous positions of the navigation system could be displayed to provide the user with a visual indication of the route travelled. This display will enable a user at a glance to see the direction in which he/she should be travelling in order to reach the destination. If the output device is a speaker 100, then the output interface can be arranged to generate a signal on demand which will cause a voice message to be output from the speaker giving an indication of the relative direction of the destination from the navigation system, for example "destination at 3 o'clock".
In an alternative embodiment, the navigation system 10 can be arranged to use the GPS receiver 60 to display an indication of the relative direction of the destination from the navigation system on the output device provided by the GPS receiver 60.
In this arrangement, the processor 30 is arranged to pass the terrestrial coordinate data retrieved by the address converter 40 to the GPS interface 70, for passing to the GPS receiver 60. The GPS receiver 60 can then use this terrestrial coordinate data to display a symbol on a display screen of the GPS receiver 60 indicating the location of the destination. In addition, in accordance with its standard operation, the GPS receiver 60 will display another symbol on the screen to indicate the current position of the GPS receiver 60.
In preferred embodiments, the terrestrial coordinate data of the destination and the navigation system are used not only to produce an indication of the relative direction of the destination from the navigation system, but may also provide an indication of the distance between the destination and the navigation system. It will be apparent that, given two sets of terrestrial coordinate data, in the form of, for example, longitude and latitude values, the processor 30 need only perform a straightforward calculation to determine the straight line distance between the two locations identified by the terrestrial coordinate data. Hence, the processor 30 can be arranged to send a signal to the output interface 80 indicating the straight line distance between the destination and the navigation system, and the output interface can be arranged to provide that information to an output device in addition to the relative direction information.
In accordance with preferred embodiments of the present invention, it is not necessary for the output device, whether it be a display device, or a speaker, to provide a continual indication of the relative direction of the destination from the navigation system. If the navigation system is being used in a vehicle, then clearly the driver will have to stay on the road network, and only needs to make any decision as to his/her route when the vehicle is approaching a junction, a turning, or any other point on the road where more than one route may be taken. Hence, in preferred embodiments, the user is able, via the key input device 110, to enter a command indicating that he/she requires an indication of the relative direction of the destination from the navigation system. For example, a specific key may be provided on the key input device 110, and the user may press this key to indicate that he/she requires the relative direction information. This command is received by the input interface 20 and passed to the processor 30. The processor 30 can then compare the terrestrial coordinate data of the destination with the terrestrial coordinate data corresponding to the navigation system's current position, or instead can instruct the GPS receiver 60 to do so, and thus cause an output signal to be generated indicating the relative direction of the destination from the navigation system. This approach minimises any user distraction caused by the navigation system, since an output is only produced by the navigation system upon request from the user.
The processing steps performed by the navigation system of preferred embodiments will now be discussed in more detail with reference to the flow diagrams of Figures 2 and 3. Figure 2 illustrates the processing steps performed in a first embodiment of the invention.
At step 200, the navigation system awaits an input from the user indicating an address of a destination, in preferred embodiments this address taking the form of a postcode. Once the postcode has been entered by the user, then that information is passed from the input interface 20 via the processor 30 to the address converter 40, where, at step 210, the address converter 40 accesses the database 50 and retrieves the terrestrial coordinate data corresponding to the postcode.
At step 220, the navigation system receives from the GPS receiver 60 the terrestrial coordinates corresponding to the current position of the navigation system.
Then, at step 230, the processor 30 within the navigation system uses both sets of terrestrial coordinate data to generate an output signal to pass to the output device, this output signal giving an indication of the relative direction of the destination from the navigation system, and in preferred embodiments also providing an indication of the straight line distance between the destination and the navigation system. This output signal is then used by the output interface 80 to cause the output device 90, 100 to output the relative direction information (and, if applicable, the straight line distance information) on the output device at step 240.
Figure 3 is a flow diagram illustrating an alternative embodiment, in which theGPS system 60 is used to provide the output. As with the process of Figure 2, the system awaits for an address input at step 300, and once the address input has been received, accesses the database 50 and retrieves the terrestrial coordinate data (step 310). At step 320, the terrestrial coordinate data for the destination is passed by the processor 30 via the GPS interface 70 to the GPS receiver 60. Then, at step 330, theGPS receiver 60 is used to produce a symbol on the screen of the GPS receiver indicating the location of the destination. Further, the GPS receiver will also produce a symbol on the screen to indicate the current position of the GPS receiver, this information being updated periodically based on signals received from the satellite 120.
The navigation system of the preferred embodiment is particularly suitable for use in a vehicle. Irrespective of which of the embodiments described above is used, as the vehicles moves, the GPS receiver continually monitors the position of the vehicle, and hence the navigation system is able to provide the relative direction information whenever required by the user. The driver will drive the vehicle towards the destination point, without the aid of a map, using any suitable road which leads towards the destination point. In preferred embodiments, each time a road junction is approached, the system can be interrogated to provide an indication of the relative direction of the destination point from the current position, and a choice can be made by the user as to which road to take based on the relative direction information. For a visual display, it would be convenient to show the destination point relative to the vehicle track line. Figures 4A and 4B show possible ways in which the display of the destination and the current position may be provided. A symbol 400 may be used to provide an indication of the current vehicle position, with a dotted line 420 or some other appropriate representation such as a history of points indicating the track taken by the vehicle. Then, symbols 410 such as a cross sign or a suitable letter, e.g. the letter "D", can be used to indicate the location of the destination. Additionally, in preferred embodiments, information about the straight line distance between the destination and the current vehicle position may be provided, for example, by a suitable indication 430 on the display screen.
For a synthesised voice system it would be convenient for the driver to request an audible instruction regarding the relative position of the destination point to the vehicle's current heading. This could be in the form of a clock face, where a 3O'clock instruction would indicate that the destination point is to the right of the current track, and a 9 O'clock instruction would indicate that the destination is to the left of the current track.
In towns and cities, there is usually a network of roads covering the complete area. Previous navigation systems have aimed to map that network of roads, and to indicate to a user the position of a vehicle within that network of roads. In contrast, a system in accordance with preferred embodiments of the present invention works on the premise that a fixed route does not have to be followed provided that an indication is given regarding the relative direction of the destination point from the vehicle's current position, and that this approach can be effective even when a map of the road network is not provided. In accordance with preferred embodiments, there is therefore no need to refer to a map of the area, but rather the driver of a vehicle merely interrogates the navigation system each time a decision has to be made, i.e. at road junctions, etc.
In rural areas, even though the network of roads is not so intense, a navigation system in accordance with preferred embodiments can be used to give a more direct route between two points without the aid of a map, and can be used to successfully navigate the vehicle to the destination point.
Whilst the most likely application for the navigation system of preferred embodiments is in motor vehicles, especially delivery vehicles, or where the driver is unable or unwilling to rely on visual interpretation of a map, with the inherent risk of unsafe driving practice, the navigation system may be employed wherever there is a need to locate a street or building address and to indicate a user's relative position with respect to that street or building address. Preferably, a navigation system in accordance with preferred embodiments may be of a size where it can be readily hand-held, and therefore can be used by a pedestrian just as easily as by a driver of a vehicle.
Although particular embodiments of the present invention have been described herein, it will be appreciated that the invention is not limited thereto, and that many modifications and additions thereto may be made within the scope of the invention.