Portable navigation devices (PNDs) that include GPS (Global Positioning System) signal reception and processing functionality are well known and are widely employed as in-car or other vehicle navigation systems.
In general terms, modern PNDs comprise a processor, memory (at least one of volatile and non-volatile, and commonly both), and map data stored within said memory. The processor and memory cooperate to provide an execution environment in which a software operating system may be established, and additionally it is commonplace for one or more additional software programs to be provided to enable the functionality of the PND to be controlled, and to provide various other functions.
Typically these devices further comprise one or more input interfaces that allow a user to interact with and control the device, and one or more output interfaces by means of which information may be relayed to the user. Illustrative examples of output interfaces include a visual display and a speaker for audible output. Illustrative examples of input interfaces include one or more physical buttons to control on/off operation or other features of the device (which buttons need not necessarily be on the device itself but could be on a steering wheel if the device is built into a vehicle), and a microphone for detecting user speech. In a particularly preferred arrangement the output interface display may be configured as a touch sensitive display (by means of a touch sensitive overlay or otherwise) to additionally provide an input interface by means of which a user can operate the device by touch.
Devices of this type will also often include one or more physical connector interfaces by means of which power and optionally data signals can be transmitted to and received from the device, and optionally one or more wireless transmitters/receivers to allow communication over cellular telecommunications and other signal and data networks, for example Wi-Fi, Wi-Max GSM and the like.
PND devices of this type also include a GPS antenna by means of which satellite-broadcast signals, including location data, can be received and subsequently processed to determine a current location of the device.
The PND device may also include electronic gyroscopes and accelerometers which produce signals that can be processed to determine the current angular and linear acceleration, and in turn, and in conjunction with location information derived from the GPS signal, velocity and relative displacement of the device and thus the vehicle in which it is mounted. Typically such features are most commonly provided in in-vehicle navigation systems, but may also be provided in PND devices if it is expedient to do so.
The utility of such PNDs is manifested primarily in their ability to determine a route between a first location (typically a start or current location) and a second location (typically a destination). These locations can be input by a user of the device, by any of a wide variety of different methods, for example by postcode, street name and house number, previously stored “well known” destinations (such as famous locations, municipal locations (such as sports grounds or swimming baths) or other points of interest), and favourite or recently visited destinations.
Typically, the PND is enabled by software for computing a “best” or “optimum” route between the start and destination address locations from the map data. A “best” or “optimum” route is determined on the basis of predetermined criteria and need not necessarily be the fastest or shortest route. The selection of the route along which to guide the driver can be very sophisticated, and the selected route may take into account existing, predicted and dynamically and/or wirelessly received traffic and road information, historical information about road speeds, and the driver's own preferences for the factors determining road choice (for example the driver may specify that the route should not include motorways or toll roads). The PND may record trip information so that the actual journey time may be recorded and fed back for more accurate prediction of how journey times vary at different times of day in accordance with habitual weight of traffic flow.
In addition, the device may continually monitor road and traffic conditions, and offer to or choose to change the route over which the remainder of the journey is to be made due to changed conditions. Real time traffic monitoring systems, based on various technologies (e.g. mobile phone data exchanges, fixed cameras, GPS fleet tracking) are being used to identify traffic delays and to feed the information into notification systems.
PNDs of this type may typically be mounted on the dashboard or windscreen of a vehicle, but may also be formed as part of an on-board computer of the vehicle radio or indeed as part of the control system of the vehicle itself. The navigation device may also be part of a hand-held system, such as a PDA (Portable Digital Assistant) a media player, a mobile phone or the like, and in these cases, the normal functionality of the hand-held system is extended by means of the installation of software on the device to perform both route calculation and navigation along a calculated route.
Route planning and navigation functionality may also be provided by a desktop or mobile computing resource running appropriate software. For example, the Royal Automobile Club (RAC) provides an on-line route planning and navigation facility which allows a user to enter a start point and a destination whereupon the server to which the user's PC is connected calculates a route (aspects of which may be user specified), generates a map, and generates a set of exhaustive navigation instructions for guiding the user from the selected start point to the selected destination. The facility also provides for pseudo three-dimensional rendering of a calculated route, and route preview functionality which simulates a user travelling along the route and thereby provides the user with a preview of the calculated route.
In the context of a PND, once a route has been calculated, the user interacts with the navigation device to select the desired calculated route, optionally from a list of proposed routes. Optionally, the user may intervene in, or guide the route selection process, for example by specifying that certain routes, roads, locations or criteria are to be avoided or are mandatory for a particular journey. The route calculation aspect of the PND forms one primary function, and navigation along such a route is another primary function.
During navigation along a calculated route, it is usual for such PNDs to provide visual and/or audible instructions to guide the user along a chosen route to the end of that route, i.e. the desired destination. It is also usual for PNDs to display map information on-screen during the navigation, such information regularly being updated on-screen so that the map information displayed is representative of the current location of the device, and thus of the user or user's vehicle if the device is being used for in-vehicle navigation.
An icon displayed on-screen typically denotes the current device location, and is centred with the map information of current and surrounding roads in the vicinity of the current device location and other map features also being displayed. Additionally, navigation information may be displayed, optionally in a status bar above, below or to one side of the displayed map information, examples of navigation information include a distance to the next deviation from the current road required to be taken by the user, the nature of that deviation possibly being represented by a further icon suggestive of the particular type of deviation, for example a left or right turn. The navigation function also determines the content, duration and timing of audible instructions by means of which the user can be guided along the route. As can be appreciated a simple instruction such as “turn left in 100 m” requires significant processing and analysis. As previously mentioned, user interaction with the device may be by a touch screen, or additionally or alternately by steering column mounted remote control, by voice activation or by any other suitable method.
A further important function provided by the device is automatic route re-calculation in the event that: a user deviates from the previously calculated route during navigation (either by accident or intentionally); real-time traffic conditions dictate that an alternative route would be more expedient and the device is suitably enabled to recognize such conditions automatically, or if a user actively causes the device to perform route re-calculation for any reason.
It is also known to allow a route to be calculated with user defined criteria; for example, the user may prefer a scenic route to be calculated by the device, or may wish to avoid any roads on which traffic congestion is likely, expected or currently prevailing. The device software would then calculate various routes and weigh more favourably those that include along their route the highest number of points of interest (known as POIs) tagged as being for example of scenic beauty, or, using stored information indicative of prevailing traffic conditions on particular roads, order the calculated routes in terms of a level of likely congestion or delay on account thereof. Other POI-based and traffic information-based route calculation and navigation criteria are also possible.
Although the route calculation and navigation functions are fundamental to the overall utility of PNDs, it is possible to use the device purely for information display, or “free-driving”, in which only map information relevant to the current device location is displayed, and in which no route has been calculated and no navigation is currently being performed by the device. Such a mode of operation is often applicable when the user already knows the route along which it is desired to travel and does not require navigation assistance.
Devices of the type described above, for example the 720T model manufactured and supplied by TomTom International B.V., provide a reliable means for enabling users to navigate from one position to another.
As mentioned above, the memory of the PND stores map data used by the PND not only to calculate routes and provide necessary navigation instructions to users, but also to provide visual information to users through the visual display of the PND.
As is known in the art, map information can be expressed in a number of ways and indeed can comprise a number of separate information components, which are used in combination by the PND. One aspect of map information is supplementary road information to provide information additional to the mere location of the road. Supplementary road information may include information about the suitability of a road for, for example, a goods-vehicle. While most roads are suitable for cars, special criteria may apply to goods-vehicles depending on their size or other criteria (for example, limits on height, weight, width; restrictions on hazardous materials; and special speed limits). As an alternative to imposing limits and restrictions, some roads may be designated as goods-vehicle-friendly or goods-vehicle-preferred, i.e. roads indicated expressly as suitable for goods-vehicles.
Map suppliers expend a lot of effort and expense in trying to ensure that goods-vehicle-specific information for a map is both comprehensive and complete. This is because goods-vehicle-specific information is not useful unless the information is reliable and complete for all areas covered by the map. For example, in order for a high goods-vehicle to pass along a calculated navigation route, any height restrictions have to be 100% correct along the entire route. It only takes one height-restricted bridge, incorrectly recorded in, or missing from, the map information to risk the goods-vehicle becoming stuck or risking collision damage to the goods-vehicle or bridge. Reliable route-planning relies on accurate goods-vehicle-specific information in the area along the entire route.
In general, there are two methods for obtaining map information, including goods-vehicle-specific information. The first is to purchase the information from government authorities and original mapping companies. However, the completeness, quality and current validity of such information may not be guaranteed, and differs from country to country. The second is to drive a vehicle equipped with special mapping equipment around the road network to collect the information using the mapping equipment. For example, the image footage from cameras mounted on the vehicle can be analysed to identify road signs depicting goods-vehicle restrictions. However, such a process is time-consuming and laborious. The task is magnified when trying to prepare accurate maps covering several countries. Moreover, the technique is limited to goods-vehicle-specific information that is signed by road signs.
There is a further aspect of goods-vehicle-specific information that is currently impossible to collect by the above mapping techniques. This is the personal knowledge or personal route preferences of experienced goods-vehicle drivers. Experienced goods-vehicle drivers build up a personal knowledge base of which routes are suitable, or they personally prefer, for their goods-vehicles (either from personal experience or from talking to other goods-vehicle drivers). For example, goods-vehicle drivers often prefer avoiding certain routes because certain turns, junctions or villages are difficult to negotiate, even though there are no formal restrictions in place preventing a goods-vehicle from using the route, or making a certain turn, or passing through the centre of a small village. Occasionally, an inexperienced goods-vehicle driver using a navigation device may cause congestion nuisance, or even building damage, by following a navigation route that is perfectly legal for the goods-vehicle, but that a driver with local knowledge would prefer not to follow. When such nuisance occurs, it can result in negative publicity. Arguably, a navigation device is intended to be at its most useful for navigating unfamiliar roads. The reaction of inconvenienced members of the public may be to criticise the use of navigation devices in general, and the embarrassed goods-vehicle driver may place less trust in a navigation device's guidance.
The present invention has been devised bearing the above issues in mind.