WO2010081542A1

WO2010081542A1 - Navigation system and method

Info

Publication number: WO2010081542A1
Application number: PCT/EP2009/050372
Authority: WO
Inventors: Hans Schulte
Original assignee: Tomtom International B.V.
Priority date: 2009-01-14
Filing date: 2009-01-14
Publication date: 2010-07-22

Abstract

A navigation system comprises an input device (220, 240) configured to enable a user to input a destination, a route planning unit (200, 210) for determining at least one route to the destination, a memory (230) for storing travel data representative of travel at different times, and a processing resource (210) operable to estimate duration or speed of travel to the destination along the or each route in dependence on the travel data, and to select a departure time for travel to the destination in dependence upon variation in estimated duration or speed of travel with departure time.

Description

Navigation system and method

Field of the Invention

The present invention relates to a navigation system and method, and in particular to a navigation system and method that can be used to estimate the shortest or quickest route to a destination. The invention relates in particular to a portable navigation device (PND).

Background to the Invention 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, a modern PNDs comprises 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 one 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 acce I ero meters 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).

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 at http://www.rac.co.uk, which facility 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 recalculation 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.

Although known devices are able to efficiently and reliably determine routes between a departure location and a destination, the time taken to travel over the determined route is inevitably subject to the amount of traffic on the route. All over the world, traffic on the road has been increasing significantly over the last few years, causing increasing traffic problems and delays, which lead in turn to irritation and stress for drivers, the wastage of fuel and negative environmental effects including sound and air pollution. In response to the increases in traffic, there have been improvements or expansions to existing roads (for example the addition of more lanes) and the construction of new roads. In addition, various traffic systems or services have been developed that enable the estimation or monitoring of traffic volumes and flows, for example RDS-TMC, TMC-Pro, VICS, HD-Traffic and IQ Routes. Such known systems or services are able to inform a user of events and delays on a route, and some of the more advanced systems or services are able to advise the user of alternative routes with lower traffic volume and/or higher traffic flow either based on current traffic data or on historic traffic data representing average travel times for the time of day and/or day of the week. However, even the most advanced systems are not able to avoid delays entirely, but instead are directed to reducing the user's delay as far as possible once traffic problems begin to occur.

In an attempt to avoid traffic problems or delays, users often resort to obtaining traffic news from the radio, TV or internet, to learning of events or roadworks that may have an effect on traffic from magazines or newspapers, and rely on their own previous experiences or those of family, friends or acquaintances in selecting the best departure time for a particular journey.

Summary of the Invention

According to a first aspect of the present invention, there is provided a navigation system comprising:- an input device configured to enable a user to input a destination; a route planning unit for determining at least one route to the destination; a memory for storing travel data representative of travel at different times; and a processing resource operable to estimate duration or speed of travel to the destination along the or each route in dependence on the travel data, and to select a departure time for travel to the destination in dependence upon variation in estimated duration or speed of travel with departure time. By selecting a departure time in dependence upon variation in estimated duration or speed of travel with departure time, the system may be able to advise the user to depart at times when delays are less likely and/or when the speed or duration of travel may be optimised. Thus, rather than only attempting to minimise delay once traffic problems occur, a technical system is provided that may assist the user to avoid traffic problems. Duration of travel may also be referred to as travel time, and the two terms may be used interchangeably.

The system preferably comprises an output device for output of the selected departure time to a user. The output device may comprise a display.

The processing resource and/or the memory and/or the output device and/or the input device and/or the route determining unit may be included in a navigation device. The navigation device may be a portable navigation device (PND). Alternatively or additionally the memory and/or the processing resource and/or the route determining unit may be included in or associated with a server. The route determining unit may be implemented, wholly or partially, in the processing resource. The processing resource may comprise a departure time module for selecting the departure time for travel to the destination.

The at least one determined route may comprise a plurality of determined routes, and selecting the departure time may comprise selecting a route from amongst the plurality of determined routes and selecting a departure time for that route.

The processing resource may be configured to select the departure time that provides the shortest estimated duration of travel or highest estimated speed of travel to the destination. Thus the travel time may be optimised.

The processing resource may be configured to compare estimated duration of travel or estimated speed of travel for each of a plurality of possible departure times to a predetermined threshold, and to select a departure time in dependence upon the comparisons.

The selecting of the departure time may comprise initially selecting a plurality of departure times and/or routes and selecting a departure time and/or route from the initially selected departure times and/or routes in dependence on user input and/or in dependence on at least one constraint. The processing resource may be configured to select the departure time subject to at least one constraint.

The at least one constraint may be a constraint on at least one of the departure time, an estimated arrival time at the destination, a property of the route, a property of travel along the route, and a property of the estimated speed or duration of travel. The at least one constraint may comprise a constraint that at least one of:- the difference between the selected departure time and a preferred departure time is minimised; the selected departure time is within a preferred range of departure times or the difference between the selected departure time and the preferred range of departure times is minimised; the estimated reliability of the estimated duration or speed of travel is greater than a predetermined reliability threshold; the route is the shortest route or the length of the route is less than a predetermined threshold length; the route does not include any roads of a predetermined type; fuel efficiency is optimised; or the estimated variability in speed along the route is below a predetermined threshold.

The input device may be configured to receive user input representative of the at least one constraint and/or for selection of the departure time from the initially selected plurality of departure times. The travel data may comprise speed data and/or duration of travel data. Alternatively or additionally the travel data may comprise at least one road type parameter representative of average speed or average duration of travel for different road types at different times and/or road type data representative of the road type or types for the or each route The processing resource may be configured to estimate the duration or speed of travel from the at least one road type parameters and the road type data.

The travel data may be representative of measured speeds or durations of travel. Alternatively or additionally, the travel data may be representative of calculated speeds or durations of travel. The travel data may comprise historic travel data and/or current travel data.

The calculated speeds or durations of travel may be interpolations or extrapolations from measured speeds or durations of travel. The calculated speeds or durations of travel may be calculated in dependence upon road types and average speeds of durations of travel for those road types.

The processing resource may be configured to estimate the speeds or durations of travel to the destination along the or each route in dependence upon at least one property of the route. The at least one property of the route may comprise at least one of road type, presence of traffic signals or other traffic control features. The navigation system may further comprise communication circuitry for communicating with at least one source of current travel data, and the processing resource is arranged to receive current travel data from the at least one source via the communication circuitry

The processing resource may be configured to update the estimates of duration or speed of travel to the destination in dependence on the received, current travel data, and/or to amend the departure time in dependence on the received, current travel data.

The processing resource may be configured to monitor receipt of the current travel data, and to update the estimates of duration or speed of travel and/or to amend the departure time, in response to receipt of current travel data. The current travel data may comprise at least one update to the travel data stored in the memory and/or comprises traffic incident data representative of a traffic incident and/or comprises weather data or other environmental data.

The navigation system may further comprise an alarm device for monitoring the difference between the departure time and the current time and for providing an alarm signal in dependence on the comparison.

The route may comprise a plurality of legs, and the processing resource may be configured to determine an estimated duration of travel or speed of travel for each leg, and to determine the estimated duration of travel or estimated speed of travel for the route from the estimated durations of travel or estimated speeds of travel for the plurality of legs. The travel data may comprise respective travel data for each leg of the route. In a further, independent aspect of the invention there is provided a navigation device comprising:- a processing resource configured to receive destination data representative of a destination, to determine an expected travel time to the destination, and to determine a departure time in dependence upon the expected travel time to the destination, subject to the constraint that the travel time to the destination is optimised; and an output device for providing the departure time to the user.

In another, independent aspect of the invention there is provided a method of selecting a departure time for travel to a destination, comprising:- determining at least one route to the destination; retrieving travel data representative of travel at different times; estimating duration or speed of travel to the destination along the or each route in dependence on the travel data; and selecting a departure time for travel to the destination in dependence upon variation in estimated duration or speed of travel with departure time.

In a further independent aspect of the invention there is provided a computer program product comprising computer executable instructions for performing a method as claimed or described herein.

The calculation of the departure time may be based on available traffic information, for example static or dynamic traffic information, historic traffic information, special event traffic information, traffic information for alternative routes, and holiday period traffic information, and/or may be based on user preferences. In another, independent aspect of the invention there is provided a computer program product comprising computer readable instructions that are executable to perform a method as claimed or described herein.

Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, apparatus features may be applied to method features and vice versa.

Brief Description of the Drawings

At least one embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic illustration of a Global Positioning System (GPS) usable by a navigation device; Figure 2 is a schematic illustration of electronic components of a navigation device;

Figure 3 is a schematic diagram of a communications system including a wireless communication channel for communication with the navigation device; Figures 4a and 4b are illustrative perspective views of a navigation device;

Figure 5 is a schematic representation of an architectural stack of the navigation device of Figure 2;

Figure 6 is an illustrative screenshot from the navigation device of Figure 2;

Figure 7 is a graph of average speed of travel as a function of time of day and day of week for a leg of a traffic network;

Figure 8 is a schematic illustration of two possible routes to a destination, each route comprising a plurality of legs;

Figure 9 is a schematic illustration of a user input screen; and

Figure 10 is a flow chart illustrating in overview a selection of a departure time.

Detailed Description of Embodiments

Embodiments of the present invention will now be described with particular reference to a PND. It should be remembered, however, that the teachings of the present invention are not limited to PNDs but are instead universally applicable to any type of processing device that is configured to execute navigation software so as to provide route planning and navigation functionality. It follows therefore that in the context of the present application, a navigation device is intended to include (without limitation) any type of route planning and navigation device, irrespective of whether that device is embodied as a PND, a navigation device built into a vehicle, for example an original equipment manufacturer (OEM) navigation device, or indeed a computing resource (such as a desktop or portable personal computer (PC), mobile telephone or portable digital assistant (PDA)) executing route planning and navigation software.

It will also be apparent from the following that the teachings of the present invention even have utility in circumstances where a user is not seeking instructions on how to navigate from one point to another, but merely wishes to be provided with a view of a given location. In such circumstances the "destination" location selected by the user need not have a corresponding start location from which the user wishes to start navigating, and as a consequence references herein to the "destination" location or indeed to a "destination" view should not be interpreted to mean that the generation of a route is essential, that travelling to the "destination" must occur, or indeed that the presence of a destination requires the designation of a corresponding start location. With the above provisos in mind, Fig. 1 illustrates an example view of Global Positioning System (GPS), usable by navigation devices. Such systems are known and are used for a variety of purposes. In general, GPS is a satellite-radio based navigation system capable of determining continuous position, velocity, time, and in some instances direction information for an unlimited number of users. Formerly known as NAVSTAR, the GPS incorporates a plurality of satellites which orbit the earth in extremely precise orbits. Based on these precise orbits, GPS satellites can relay their location to any number of receiving units.

The GPS system is implemented when a device, specially equipped to receive GPS data, begins scanning radio frequencies for GPS satellite signals. Upon receiving a radio signal from a GPS satellite, the device determines the precise location of that satellite via one of a plurality of different conventional methods. The device will continue scanning, in most instances, for signals until it has acquired at least three different satellite signals (noting that position is not normally, but can be determined, with only two signals using other triangulation techniques). Implementing geometric triangulation, the receiver utilizes the three known positions to determine its own two-dimensional position relative to the satellites. This can be done in a known manner. Additionally, acquiring a fourth satellite signal will allow the receiving device to calculate its three dimensional position by the same geometrical calculation in a known manner. The position and velocity data can be updated in real time on a continuous basis by an unlimited number of users.

As shown in Figure 1 , the GPS system is denoted generally by reference numeral 100. A plurality of satellites 120 are in orbit about the earth 124. The orbit of each satellite 120 is not necessarily synchronous with the orbits of other satellites 120 and, in fact, is likely asynchronous. A GPS receiver 140 is shown receiving spread spectrum GPS satellite signals 160 from the various satellites 120.

The spread spectrum signals 160, continuously transmitted from each satellite 120, utilize a highly accurate frequency standard accomplished with an extremely accurate atomic clock. Each satellite 120, as part of its data signal transmission 160, transmits a data stream indicative of that particular satellite 120. It is appreciated by those skilled in the relevant art that the GPS receiver device 140 generally acquires spread spectrum GPS satellite signals 160 from at least three satellites 120 for the GPS receiver device 140 to calculate its two-dimensional position by triangulation. Acquisition of an additional signal, resulting in signals 160 from a total of four satellites 120, permits the GPS receiver device 140 to calculate its three-dimensional position in a known manner. Figure 2 is an illustrative representation of electronic components of a navigation device 200 according to an embodiment of the present invention, in block component format. It should be noted that the block diagram of the navigation device 200 is not inclusive of all components of the navigation device, but is only representative of many example components.

The navigation device 200 is located within a housing (not shown). The housing includes a processor 210 connected to an input device 220 and a display screen 240. The input device 220 can include a keyboard device, voice input device, touch panel and/or any other known input device utilised to input information; and the display screen 240 can include any type of display screen such as an LCD display, for example. In one arrangement the input device 220 and display screen 240 are integrated into an integrated input and display device, including a touchpad or touchscreen input so that a user need only touch a portion of the display screen 240 to select one of a plurality of display choices or to activate one of a plurality of virtual buttons. The navigation device may include an output device 260, for example an audible output device (e.g. a loudspeaker). As output device 260 can produce audible information for a user of the navigation device 200, it is should equally be understood that input device 240 can include a microphone and software for receiving input voice commands as well. In the navigation device 200, processor 210 is operatively connected to and set to receive input information from input device 220 via a connection 225, and operatively connected to at least one of display screen 240 and output device 260, via output connections 245, to output information thereto. Further, the processor 210 is operably coupled to a memory resource 230 via connection 235 and is further adapted to receive/send information from/to input/output (I/O) ports 270 via connection 275, wherein the I/O port 270 is connectible to an I/O device 280 external to the navigation device 200. The memory resource 230 comprises, for example, a volatile memory, such as a Random Access Memory (RAM) and a non-volatile memory, for example a digital memory, such as a flash memory. The external I/O device 280 may include, but is not limited to an external listening device such as an earpiece for example. The connection to I/O device 280 can further be a wired or wireless connection to any other external device such as a car stereo unit for hands-free operation and/or for voice activated operation for example, for connection to an ear piece or head phones, and/or for connection to a mobile phone for example, wherein the mobile phone connection may be used to establish a data connection between the navigation device 200 and the internet or any other network for example, and/or to establish a connection to a server via the internet or some other network for example.

Fig. 2 further illustrates an operative connection between the processor 210 and an antenna/receiver 250 via connection 255, wherein the antenna/receiver 250 can be a GPS antenna/receiver for example. It will be understood that the antenna and receiver designated by reference numeral 250 are combined schematically for illustration, but that the antenna and receiver may be separately located components, and that the antenna may be a GPS patch antenna or helical antenna for example.

Further, it will be understood by one of ordinary skill in the art that the electronic components shown in Fig. 2 are powered by power sources (not shown) in a conventional manner. As will be understood by one of ordinary skill in the art, different configurations of the components shown in Fig. 2 are considered to be within the scope of the present application. For example, the components shown in Fig. 2 may be in communication with one another via wired and/or wireless connections and the like. Thus, the scope of the navigation device 200 of the present application includes a portable or handheld navigation device 200.

In addition, the portable or handheld navigation device 200 of Fig. 2 can be connected or "docked" in a known manner to a vehicle such as a bicycle, a motorbike, a car or a boat for example. Such a navigation device 200 is then removable from the docked location for portable or handheld navigation use. Referring now to Fig. 3, the navigation device 200 may establish a "mobile" or telecommunications network connection with a server 302 via a mobile device (not shown) (such as a mobile phone, PDA, and/or any device with mobile phone technology) establishing a digital connection (such as a digital connection via known Bluetooth technology for example). Thereafter, through its network service provider, the mobile device can establish a network connection (through the internet for example) with a server 302. As such, a "mobile" network connection is established between the navigation device 200 (which can be, and often times is mobile as it travels alone and/or in a vehicle) and the server 302 to provide a "real-time" or at least very "up to date" gateway for information. The establishing of the network connection between the mobile device (via a service provider) and another device such as the server 302, using an internet (such as the World Wide Web) for example, can be done in a known manner. This can include use of TCP/IP layered protocol for example. The mobile device can utilize any number of communication standards such as CDMA, GSM, WAN, etc. As such, an internet connection may be utilised which is achieved via data connection, via a mobile phone or mobile phone technology within the navigation device 200 for example. For this connection, an internet connection between the server 302 and the navigation device 200 is established. This can be done, for example, through a mobile phone or other mobile device and a GPRS (General Packet Radio Service)- connection (GPRS connection is a high-speed data connection for mobile devices provided by telecom operators; GPRS is a method to connect to the internet).

The navigation device 200 can further complete a data connection with the mobile device, and eventually with the internet and server 302, via existing Bluetooth technology for example, in a known manner, wherein the data protocol can utilize any number of standards, such as the GSRM, the Data Protocol Standard for the GSM standard, for example.

The navigation device 200 may include its own mobile phone technology 272 within the navigation device 200 itself (including an antenna for example, or optionally using the internal antenna of the navigation device 200). The mobile phone technology within the navigation device 200 can include internal components as specified above, and/or can include an insertable card (e.g. Subscriber Identity Module or SIM card), complete with necessary mobile phone technology and/or an antenna for example. As such, mobile phone technology within the navigation device 200 can similarly establish a network connection between the navigation device 200 and the server 302, via the internet for example, in a manner similar to that of any mobile device. For GPRS phone settings, a Bluetooth enabled navigation device may be used to correctly work with the ever changing spectrum of mobile phone models, manufacturers, etc., model/manufacturer specific settings may be stored on the navigation device 200 for example. The data stored for this information can be updated.

In Fig. 3 the navigation device 200 is depicted as being in communication with the server 302 via a generic communications channel 318 that can be implemented by any of a number of different arrangements. The server 302 and a navigation device 200 can communicate when a connection via communications channel 318 is established between the server 302 and the navigation device 200 (noting that such a connection can be a data connection via mobile device, a direct connection via personal computer via the internet, etc.).

The server 302 includes, in addition to other components which may not be illustrated, a processor 304 operatively connected to a memory 306 and further operatively connected, via a wired or wireless connection 314, to a mass data storage device 312. The processor 304 is further operatively connected to transmitter 308 and receiver 310, to transmit and send information to and from navigation device 200 via communications channel 318. The signals sent and received may include data, communication, and/or other propagated signals. The transmitter 308 and receiver 310 may be selected or designed according to the communications requirement and communication technology used in the communication design for the navigation system 200. Further, it should be noted that the functions of transmitter 308 and receiver 310 may be combined into a signal transceiver.

Server 302 is further connected to (or includes) a mass storage device 312, noting that the mass storage device 312 may be coupled to the server 302 via communication link 314. The mass storage device 312 contains a store of navigation data and map information, and can again be a separate device from the server 302 or can be incorporated into the server 302.

The navigation device 200 is adapted to communicate with the server 302 through communications channel 318, and includes processor, memory, etc. as previously described with regard to Fig. 2, as well as transmitter 320 and receiver 322 to send and receive signals and/or data through the communications channel 318, noting that these devices can further be used to communicate with devices other than server 302. Further, the transmitter 320 and receiver 322 are selected or designed according to communication requirements and communication technology used in the communication design for the navigation device 200 and the functions of the transmitter 320 and receiver 322 may be combined into a single transceiver. Software stored in server memory 306 provides instructions for the processor

304 and allows the server 302 to provide services to the navigation device 200. One service provided by the server 302 involves processing requests from the navigation device 200 and transmitting navigation data from the mass data storage 312 to the navigation device 200. Another service provided by the server 302 includes processing the navigation data using various algorithms for a desired application and sending the results of these calculations to the navigation device 200.

The communication channel 318 generically represents the propagating medium or path that connects the navigation device 200 and the server 302. Both the server 302 and navigation device 200 include a transmitter for transmitting data through the communication channel and a receiver for receiving data that has been transmitted through the communication channel.

The communication channel 318 is not limited to a particular communication technology. Additionally, the communication channel 318 is not limited to a single communication technology; that is, the channel 318 may include several communication links that use a variety of technology. For example, the communication channel 318 can be adapted to provide a path for electrical, optical, and/or electromagnetic communications, etc. As such, the communication channel 318 includes, but is not limited to, one or a combination of the following: electric circuits, electrical conductors such as wires and coaxial cables, fibre optic cables, converters, radio-frequency (RF) waves, the atmosphere, empty space, etc. Furthermore, the communication channel 318 can include intermediate devices such as routers, repeaters, buffers, transmitters, and receivers, for example.

In one illustrative arrangement, the communication channel 318 includes telephone and computer networks. Furthermore, the communication channel 318 may be capable of accommodating wireless communication such as radio frequency, microwave frequency, infrared communication, etc. Additionally, the communication channel 318 can accommodate satellite communication.

The communication signals transmitted through the communication channel 318 include, but are not limited to, signals as may be required or desired for given communication technology. For example, the signals may be adapted to be used in cellular communication technology such as Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), etc. Both digital and analogue signals can be transmitted through the communication channel 318. These signals may be modulated, encrypted and/or compressed signals as may be desirable for the communication technology.

The server 302 includes a remote server accessible by the navigation device 200 via a wireless channel. The server 302 may include a network server located on a local area network (LAN), wide area network (WAN), virtual private network (VPN), etc.

The server 302 may include a personal computer such as a desktop or laptop computer, and the communication channel 318 may be a cable connected between the personal computer and the navigation device 200. Alternatively, a personal computer may be connected between the navigation device 200 and the server 302 to establish an internet connection between the server 302 and the navigation device 200. Alternatively, a mobile telephone or other handheld device may establish a wireless connection to the internet, for connecting the navigation device 200 to the server 302 via the internet.

The navigation device 200 may be provided with information from the server 302 via information downloads which may be periodically updated automatically or upon a user connecting navigation device 200 to the server 302 and/or may be more dynamic upon a more constant or frequent connection being made between the server 302 and navigation device 200 via a wireless mobile connection device and TCP/IP connection for example. For many dynamic calculations, the processor 304 in the server 302 may be used to handle the bulk of the processing needs, however, processor 210 of navigation device 200 can also handle much processing and calculation, oftentimes independent of a connection to a server 302. As indicated above in Fig. 2, a navigation device 200 includes a processor 210, an input device 220, and a display screen 240. The input device 220 and display screen 240 are integrated into an integrated input and display device to enable both input of information (via direct input, menu selection, etc.) and display of information through a touch panel screen, for example. Such a screen may be a touch input LCD screen, for example, as is well known to those of ordinary skill in the art. Further, the navigation device 200 can also include any additional input device 220 and/or any additional output device 241 , such as audio input/output devices for example.

Figs 4A and 4B are perspective views of a navigation device 200. As shown in Fig. 4A, the navigation device 200 may be a unit that includes an integrated input and display device 290 (a touch panel screen for example) and the other components of fig. 2 (including but not limited to internal GPS receiver 250, microprocessor 210, a power supply, memory systems 230, etc.).

The navigation device 200 may sit on an arm 292, which itself may be secured to a vehicle dashboard/window/etc, using a suction cup 294. This arm 292 is one example of a docking station to which the navigation device 200 can be docked.

As shown in Fig. 4B, the navigation device 200 can be docked or otherwise connected to an arm 292 of the docking station by snap connecting the navigation device 292 to the arm 292 for example. The navigation device 200 may then be rotatable on the arm 292, as shown by the arrow of Fig. 4B. To release the connection between the navigation device 200 and the docking station, a button on the navigation device 200 may be pressed, for example. Other equally suitable arrangements for coupling and decoupling the navigation device to a docking station are well known to persons of ordinary skill in the art.

Referring now to Fig. 5 of the accompanying drawings, the memory resource 230 stores a boot loader program (not shown) that is executed by the processor 210 in order to load an operating system 470 from the memory resource 230 for execution by functional hardware components 460, which provides an environment in which application software 480 can run. The operating system 470 serves to control the functional hardware components 460 and resides between the application software 480 and the functional hardware components 460. The application software 480 provides an operational environment including the GUI that supports core functions of the navigation device 200, for example map viewing, route planning, navigation functions and any other functions associated therewith. In accordance with the embodiment described in more detail below, the application software 480 includes a departure time module 490.

When the user switches on the device 200, the device 200 acquires a GPS fix and calculates (in a known manner) the current location of the navigation device 200. The user is then presented, as shown in Figure 6, with a view in pseudo three dimensions on a touch screen display 240 of the local environment 502 in which the navigation device 200 is determined to be located, and in a region 504 of the display 240 below the local environment a series of control and status messages. The device 200 provides route planning, mapping and navigation functions to the user, in dependence on user input provided by a series of interlinked soft or virtual buttons and menu screens that can be displayed on the display 240.

In addition to providing route planning, mapping and navigation functions, the device 200 is also able to determine departure times for a particular route, via operation of the departure time module 490 that is included in the application software 480 of the processor 210.

The departure time module 490 is linked to the memory 230 and to the communication channel 318. The departure time module 490 is also linked to a route planning unit in the form of a route planning module (not shown) included in the application software 480, which implements the route planning functionality of the device 200.

In operation, the departure time module 490 receives route data representative of possible routes to a destination determined by the route planning module. The departure time module 490 then requests and receives, from either the memory 230 or the server 302 via communications channel 318, travel data representative of travel at different times along each of the selected routes.

The travel data received by the departure time module 490 comprises data that is representative of travel at different times, and usually comprises durations or speeds of travel along the selected routes at different times. The travel data can be static, and thus does not change, or dynamic, and thus subject to regular or occasional updates. It has been found that durations or speeds of travel vary significantly but predictably depending on the time of day, and day of the week. The travel data comprises one or more of historic travel data, current travel data and generic speed/distance data (also referred to as predicted travel data). The departure time module 490 determines an estimated duration of travel (or estimated average speed of travel) for each of the routes for different departure times, based upon the travel data, and determines which of the departure times and routes provides the shortest expected duration of travel (or highest average speed of travel). The departure module 490 then selects a departure time in order to optimise duration of travel (or average speed of travel) based upon the travel data. In a variant of the mode of operation described in the preceding paragraph, the departure time module 490 initially selects a plurality or range of possible departure times. The initially selected departure times are usually departure times that provide estimated durations of travel (or estimated average speeds of travel) that are less than (or greater than) a predetermined threshold. Thus, possible departure times that provide acceptable duration or speed of travel are selected. A departure time is then selected from amongst the initially selected departure times, either based upon an additional constraint, or by user selection. Examples of some additional constraints on selection of route pr departure time are described below.

As mentioned above, the travel data can comprise historic travel data, which usually comprises actual measured average speed data. The average speed data is provided as a function of time of day, and day of the week.

An example of a plot of average speed as a function of time of day and different days of the week for one leg (for example, a stretch of road between successive nodes or junctions) of a traffic network is provided in Figure 7. Historic travel data can be obtained from anonymous GPS data logged by PND users. Usually such GPS data is logged every five seconds by each PND and later transmitted back to the server 302 (anonymously and subject to permission from the user) via the internet when the PND is docked in a home platform. In the case of the embodiment described herein the historic data comprises historic speed profiles as used in the TomTom IQ Routes (RTM) system. It can be seen from Figure 7 that there are times during each day when average speeds for the leg that is the subject of Figure 7 are higher than at other times. In a simple example, if a user wished to travel from one end of the leg to the other on, say, Monday morning between 8am and 12pm, the departure time module 490 would select a departure time of around 10.30 am as expected travel speeds would be expected to be highest (and thus travel duration would be expected to be lowest) at that time. In another example, if the user wished to travel at any time or day of the week, the departure time module 490 would select a departure time of around 2am on Sunday morning.

The historic traffic data can include historic data concerning traffic incidents, for example the rate of occurrence of traffic jams, as a function of time (for example as a function of time of day and/or day of week). In that case, the departure time module 490 can select departure times that reduce or minimise the chances of encountering a traffic jam.

In practice, most journeys comprise multiple legs, and in such cases the departure time module 490 processes travel data for each leg, and usually considers more than one route, in order to calculate a route and departure time that optimises expected travel duration. For example, in Figure 8, two possible routes are selected by the route determination module between a departure point 520 and a destination 522. The first route is made up of legs 524, 526, 528, 530 and the second route is made up of legs 524, 526, 534, 536. It can be seen that both routes have legs 524, 526 in common. The departure time module 490 requests and receives travel data from the memory 230 or the server 302 for each of the legs 524, 526, 528, 530, 534, 536, and determines the expected duration of travel for each leg for different departure times. The departure time module 490 then sums the expected duration of travel for each leg of each route, for each different departure time, and determines the route and the departure time that provides the shortest duration of travel for the journey between the departure point 520 and the destination 522.

Usually the departure time module 490 calculates expected duration of travel for a series of different departure times spaced by a predetermined time interval (for example 5 minutes or 15 minutes) and selects a departure time from the series of different departure times. Alternatively or additionally, the departure time module 490 interpolates or extrapolates, or fits a function to, the variation of duration of travel with departure time and determines an optimal departure time from the interpolation, extrapolation or fitted function.

As well as historic data, the travel data can also include generic speed/distance data based on road type. Speed/distance data based on road type is used by the departure time module 490 in cases where historic travel data is not available for a particular leg, or has been found to be unreliable. Speed/distance data comprises a speed of travel assigned to a particular road type (for example, 30 km/hour for a minor, urban road, 60km/hour for an arterial, urban road, 90 km/hour for a motorway), which can be adjusted in dependence on the time of travel, for example by assigning a higher average speed for quieter times of day (for example during the night) and a lower average speed for busier times (for example, rush hour). The speed/distance data can be obtained by averaging historical travel data obtained from many different roads of a particular type. The departure time module 490 performs a speed/distance calculation for the leg, using the predicted speed of travel for that leg based on road type obtained from the speed/distance data, adjusted for the time of travel. More categories of road can be provided than those mentioned in the preceding paragraph, and different predicted speeds provided for each category. It has been found that in reality speeds vary between roads, even of the same type. For example, a variation of average speeds may be due to the presence of additional road features, for example roundabouts and traffic lights, and the calculation of expected duration or speed of travel can be adjusted to take account of the presence of such road features. Predicted speeds can also be varied by the departure time module 490 in dependence on weather conditions and/or the occurrence of traffic problems or events, that may cause delays. The duration of travel for a route is then estimated in dependence on the predicted speeds and any predicted delays.

As mentioned above, the travel data can comprise current travel data as well as or instead of historic travel data. Current travel data provides an indication of current travel conditions, and can be used to update or modify historic travel data or generic speed/distance data or estimates or selections based on historic travel data or generic speed/distance data. Current travel conditions are considered to be travel conditions pertaining at the current time, or recently, for example within the last hour, several hours or day.

Current travel data is received by the device 200 from the server 302 or from one or more other travel data sources via communications channel 312 using communication circuitry, in the form of mobile phone technology 272, included in the device 200, and is either passed directly to the departure time module 490, or stored in the memory 230, for subsequent retrieval by the departure time module 490.

Estimated durations or speeds of travel are modified, or determined, by the departure time module 490 in dependence on the received current travel data. In the example described herein the current travel data comprises average speed data for different legs of a traffic network gathered over a short, recent time window (for example, a 30 minute window within the last hour). The average speed data can be obtained from anonymous GPS data obtained from mobile phones associated with registered PND users, for example using the TomTom HDTraffic (RTM) system. Current travel data can also comprise data relating to weather or other environmental condition, or warning data concerning roadworks or events, each of which may cause a variation in traffic speeds.

The traffic data can also include special event traffic data, and traffic data in respect of holiday periods, which represent or can be used to estimate modifications to travel duration or speed due to the occurrence of special events (such as road closures, or large sporting, musical or other cultural events) or at holiday times.

The departure time module 490 is operable to update the calculation of estimated durations or speeds of travel, and/or to amend the selected departure time and/or route, in dependence upon current travel data. For example, if current travel data indicates that there are significant delays on a selected route, then the departure time module 490 may select an alternative route and determine an optimal departure time for that route. Alternatively, the departure time module 490 can suggest a later departure time for the selected route, in anticipation of the delays for the route having cleared at that later time.

As well as selecting the departure time that it estimates will provide the shortest duration of travel or greatest average speed of travel, the departure time module 490 is also configured to be able to place one or more constraints on the departure time, arrival time, or route on one or more properties of the route or travel along the route. The constraints can be selected by the user via operation of a user input screen.

An example of a user input screen, displayed on display 240, that enables the user to place a constraint on the departure time is illustrated in Figure 9. The user input screen comprises a destination box 540 that indicates the destination that has been selected by the user, an input box 542 that enables input by a user of a day of travel via operation of selection button 544, and time input boxes 546, 550 that enable input by a user of earliest and latest times of departure via operation of selection buttons 548, 552. The screen also includes a display region 554 for displaying the departure time determined by the departure time module 490, and an alarm button 556 that enables the user to set an alarm to be provided at the departure time, or at a predetermined time (for example 5 minutes) before the departure time. The processor 210 includes an alarm device (not shown) that is configured to provide an alarm signal at the departure time, or at a predetermined time (for example 5 minutes) before the departure time if the alarm is set. The output device 260 is responsive to the alarm signal to provide an audible, visual or tactile output.

In operation, the user can input a range of times within which they wish to depart, using the input boxes 546, 550 and a day or days of departure using the input box 542. Thus, the user is able to place a constraint on the departure time. The departure module then determines the departure time within the selected range that provides the shortest estimated duration of travel, and outputs the determined departure time in the display region 554.

If the user leaves the box 542 empty then the departure time module 490 determines the optimal departure time today. If the user selects the option "any day" in the box 542 then the departure time module 490 selects the day and time which provides the shortest duration of travel, without any constraint on the day of travel.

The constraints that may be placed on the determination of departure time are not limited to those described in relation to the input screen of Figure 9. For example, the user may select a desired arrival time or range of desired arrival times rather than a desired departure time or range of desired departure times. In another embodiment, the user selects a threshold duration, and the departure module 490 determines and initially selects those departure times or ranges of departure times that are estimated to provide a duration of travel less than the threshold duration, and either displays those departure times or ranges of departure times to the user or selects a departure time from amongst those departure times or ranges of departure times. In one variant of that embodiment, the user selects a desired departure (or arrival time) and the departure time module 490 selects the departure time that is closest to the desired departure time (or provides an estimated arrival time closest to the desired arrival time) and that also provides an estimated duration of travel that is less than the threshold duration.

In another embodiment, the travel data includes a reliability parameter that represents the reliability of the estimated time of travel or speed for each leg. In the case of historical travel data the reliability parameter may be or may represent the variance of the measured time or speed data. The user is able to select a level of reliability for the estimated duration of travel and the departure time module 490 selects a departure time that provides the selected level of reliability of the duration of travel. In a situation where the departure time module 490 determines that there are two or more departure times that provide substantially the same estimated duration of travel, the departure time module 490 selects the departure time that provides the most reliably estimated duration of travel.

In further embodiments, routes are selected in dependence on other factors as well as, or instead of, shortest expected duration (or highest average speed) of travel, optionally subject to any constraints on the departure time or duration of travel. For example, the user is able to specify a constraint that the selected route should be the shortest route (or be below a threshold length), or that the route should exclude routes of a certain type or that the fuel efficiency should be optimised (or should be above a threshold amount). The selection may be subject to road constraints (such as a requirement to avoid motorways, ferrys, tunnels, or toll roads, or to minimize the number of traffic lights) vehicle constraints (such as a requirement that the route should be suitable for a vehicle of a particular height, length or axle pressure) or other criteria (for example, a requirement to follow a scenic route, or to include or exclude particular via points or via areas). The stages of operation of one embodiment are illustrated in overview in Figure

10. In the first stage 560 input is received from a user selecting a destination and any constraints on departure time, arrival time or route characteristics or criteria. In the next stage 562 possible routes to the destination are determined, and in the subsequent stage 564 the duration of travel or average speed of travel as a function of departure time is estimated for each route. In the next stage 566 the departure time and route that provides the shortest estimated duration of travel or highest estimated speed of travel is selected, subject to any constraints. In the final stage 568, the selected departure time(s) for one or more routes are displayed to a user.

The embodiments described above in relation to Figures 8 to 10 provide a system or service that is able to tell a user the best time for his or her departure for different routes from a departure location to a destination, according to his or her preferences. The user knows in advance, before commencing their journey, expected travel times and best routes, according to his or her preferences. Effects such as the loss or wasting of time, irritation and stress, wasting of fuel and negative environmental effects can be reduced. The embodiments also enable the smoothing of traffic peaks, when used by a significant number of users, as more users may be prompted to travel outside peak periods.

It will be appreciated that whilst various aspects and embodiments of the present invention have heretofore been described, the scope of the present invention is not limited to the particular arrangements set out herein and instead extends to encompass all arrangements, and modifications and alterations thereto, which fall within the scope of the appended claims.

For example, although the present invention may be exemplified as a portable navigation device, it would be appreciated that 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 online route planning and navigation facility at http://www.rac.co.uk, which facility allows a user to enter a start point and a destination whereupon the server with which the user's computing resource is communicating 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.

Whilst embodiments described in the foregoing detailed description refer to GPS, it should be noted that the navigation device may utilise any kind of position sensing technology as an alternative to (or indeed in addition to) GPS. For example the navigation device may utilise using other global navigation satellite systems such as the European Galileo system. Equally, it is not limited to satellite based but could readily function using ground based beacons or any other kind of system that enables the device to determine its geographic location.

Alternative embodiments of the invention can be implemented as a computer program product for use with a computer system, the computer program product being, for example, a series of computer instructions stored on a tangible data recording medium, such as a diskette, CD-ROM, ROM, or fixed disk, or embodied in a computer data signal, the signal being transmitted over a tangible medium or a wireless medium, for example, microwave or infrared. The series of computer instructions can constitute all or part of the functionality described above, and can also be stored in any memory device, volatile or non-volatile, such as semiconductor, magnetic, optical or other memory device.

It will also be well understood by persons of ordinary skill in the art that whilst the embodiment implement certain functionality by means of software, that functionality could equally be implemented solely in hardware (for example by means of one or more ASICs (application specific integrated circuit)) or indeed by a mix of hardware and software. As such, the scope of the present invention should not be interpreted as being limited only to being implemented in software.

It will be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention. Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.

Lastly, it should also be noted that whilst the accompanying claims set out particular combinations of features described herein, the scope of the present invention is not limited to the particular combinations hereafter claimed, but instead extends to encompass any combination of features or embodiments herein disclosed irrespective of whether or not that particular combination has been specifically enumerated in the accompanying claims at this time.

Claims

1 . A navigation system comprising :- an input device (220, 240) configured to enable a user to input a destination; a route planning unit (200, 210) for determining at least one route to the destination; a memory (230) for storing travel data representative of travel at different times; and a processing resource (210) operable to estimate duration or speed of travel to the destination along the or each route in dependence on the travel data, and to select a departure time for travel to the destination in dependence upon variation in estimated duration or speed of travel with departure time.

2. A navigation system according to Claim 1 , wherein the processing resource (210) is configured to select the departure time that provides the shortest estimated duration of travel or highest estimated speed of travel to the destination.

3. A navigation system according to Claim 1 or 2, wherein the processing resource (210) is configured to compare estimated duration of travel or estimated speed of travel for each of a plurality of possible departure times to a predetermined threshold, and to select a departure time in dependence upon the comparisons.

4. A navigation system according to any preceding claim, wherein the selecting of the departure time comprises initially selecting a plurality of departure times and/or routes and selecting a departure time and/or route from the initially selected departure times and/or routes in dependence on user input and/or in dependence on at least one constraint.

5. A navigation system according to any preceding claim, wherein the processing resource (210) is configured to select the departure time subject to at least one constraint.

6. A navigation system according to Claim 4 or 5, wherein the at least one constraint is a constraint on at least one of the departure time, an estimated arrival time at the destination, a property of the route, a property of travel along the route, and a property of the estimated speed or duration of travel.

7. A navigation system according to any of Claims 4 to 6, wherein the at least one constraint comprises a constraint that at least one of:- the difference between the selected departure time and a preferred departure time is minimised; the selected departure time is within a preferred range of departure times or the difference between the selected departure time and the preferred range of departure times is minimised; the estimated reliability of the estimated duration or speed of travel is greater than a predetermined reliability threshold; the route is the shortest route or the length of the route is less than a predetermined threshold length; the route does not include any roads of a predetermined type; fuel efficiency is optimised; or the estimated variability in speed along the route is below a predetermined threshold.

8. A navigation system according to any preceding claim, wherein the travel data comprises speed data and/or duration of travel data.

9. A navigation system according to any preceding claim, wherein the travel data is representative of measured speeds or durations of travel.

10. A navigation system according to any preceding claim, wherein the travel data is representative of calculated speeds or durations of travel.

1 1 . A navigation system according to any preceding claim, wherein the travel data comprises historic travel data and/or current travel data.

12. A navigation system according to any preceding claim, further comprising communication circuitry (272) for communicating with at least one source of current travel data, and the processing resource is arranged to receive current travel data from the at least one source via the communication circuitry

13. A navigation system according to Claim 1 1 , wherein the processing resource is configured to update the estimates of duration or speed of travel to the destination in dependence on the received, current travel data, and/or to amend the departure time in dependence on the received, current travel data.

14. A navigation system according to Claim 12 or 13, wherein the current travel data comprises at least one update to the travel data stored in the memory and/or comprises traffic incident data representative of a traffic incident and/or comprises weather data or other environmental data.

15. A navigation system according to any preceding claim, further comprising an alarm device for monitoring the difference between the departure time and the current time and for providing an alarm signal in dependence on the comparison.

16. A navigation device (200) comprising:- a processing resource (210) configured to receive destination data representative of a destination, to determine an expected travel time to the destination, and to determine a departure time in dependence upon the expected travel time to the destination, subject to the constraint that the travel time to the destination is optimised; and an output device (260) for providing the departure time to the user.

17. A method of selecting a departure time for travel to a destination, comprising:- determining at least one route to the destination; retrieving travel data representative of travel at different times; estimating duration or speed of travel to the destination along the or each route in dependence on the travel data; and selecting a departure time for travel to the destination in dependence upon variation in estimated duration or speed of travel with departure time.

18. A computer program product comprising computer executable instructions for performing a method according to Claim 17.