WO2015144921A1

WO2015144921A1 - Method and apparatus for generating a map of the terrain in a geographic area

Info

Publication number: WO2015144921A1
Application number: PCT/EP2015/056810
Authority: WO
Inventors: Hendrik Sebastian ZIEZOLD; Pavel SENYUSHKIN
Original assignee: Tomtom International B.V.
Priority date: 2014-03-27
Filing date: 2015-03-27
Publication date: 2015-10-01
Also published as: GB201405540D0

Abstract

An apparatus, method and a computer program for generating map of the terrain in a geographic area is provided. The method comprises: determining, for each of a plurality of pixels, an elevation value from digital terrain data for the portion of the geographic area represented by the pixel; determining, for each of the plurality of pixels, at least one parameter from parameter data different from the elevation value for the portion of the geographic area represented by the pixel; using the elevation value and the at least one parameter, for each of the plurality of pixels, to select a colour for the pixel from one or more predetermined texture files; using the digital terrain data to determine, for each of the plurality of pixels, a normal to the terrain of the geographic area represented by the pixel, and using the determined normal and a determined direction of sunlight, for each of the plurality of pixels, to determine a shading for the pixel; and generating the map for display on the display device by applying the selected colour and determined shading to each of the plurality of pixels.

Description

METHOD AND APPARATUS FOR GENERATING A MAP OF

THE TERRAIN IN A GEOGRAPHIC AREA Field of the Invention

Embodiments of the present invention relate to generating at least part of a map for display on a display of a computing device. In particular, they relate to generating one or more terrain portions of a map for display on a display of a computing device. Illustrative embodiments of the invention relate to portable navigation devices (so-called PNDs), in particular PNDs that include Global Positioning System (GPS) signal reception and processing functionality.

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 PND 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 necessa ly 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 historical, existing and/or predicted traffic and road information.

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, an on-line route planning and navigation facility is provided at routes.tomtom.com, 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 the current road 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.

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 provide a reliable means for enabling users to navigate from one position to another.

The Applicant has recognised that the functionality of such devices can be enhanced though the visualisation of additional data, such as elevation data, environment data, etc. The processing of such data for display, however, can be problematic on the limited processing capabilities of portable computing devices. Summary of the Invention

In accordance with a first aspect of the invention there is provided a method, comprising:

determining an elevation value, for a pixel, from digital terrain data;

determining one or more parameters, different from the elevation value, for the pixel;

using at least the elevation value and the one or more parameters to select a colour for the pixel from one or more predetermined texture files; and causing colour to be applied to the pixel using the selected colour.

The present invention extends to an apparatus, preferably a navigation device, for carrying out a method in accordance with any of the aspects or embodiments of the invention herein desc bed.

Thus, in accordance with a second aspect of the invention there is provided an apparatus, comprising:

means for determining an elevation value, for a pixel, from digital terrain data;

means for determining one or more parameters, different from the elevation value, for the pixel; means for using at least the elevation value and the one or more parameters to select a colour for the pixel from one or more predetermined texture files; and

means for causing colour to be applied to the pixel using the selected colour.

As will be appreciated by those skilled in the art, this further aspect of the present invention can and preferably does include any one or more or all of the preferred and optional features of the invention desc bed herein in respect of any of the other aspects of the invention, as appropriate. If not explicitly stated, the apparatus of the present invention herein may comprise means for carrying out any step deschbed in relation to the method of the invention in any of its aspects or embodiments, and vice versa.

The present invention is a computer implemented invention, and any of the steps deschbed in relation to any of the aspects or embodiments of the invention may be carried out under the control of a set of one or more processors. The means for carrying out any of the steps deschbed in relation to the system may be a set of one or more processors.

In general, the apparatus of the present invention in any of its embodiments may be at least one processing device. The or a processing device may be a navigation device, whether a portable navigation device (PND) or an integrated device, or may be a server.

In embodiments where the method is implemented on a navigation device, the device comprises position detection means for determining the position of the device, e.g. a global navigation satellite system (GNSS), e.g. GPS or GLONASS, receiver. As will be appreciated the device may use other means for determining its current location as desired, e.g. terrestrial beacons, the mobile

telecommunications network, etc.

In embodiments, the one or more parameters are one or more environmental parameters, optionally relating to the natural environment. The one or more parameters may comprise a thermal parameter. The one or more parameters may comprise a parameter at least partially based on precipitation.

In embodiments, the pixel represents a geographic location on a map.

In embodiments, the method further comprises determining a direction of sunlight from stored sunlight information, and using the determined direction of sunlight to shade the pixel.

The direction of sunlight may be variable, and the direction of sunlight may be determined based on the current time of day and a geographic location of the pixel. In such embodiments, the method may further comprise determining a terrain normal for the pixel, and using the direction of sunlight, in combination with the terrain normal for the pixel, to determine shading for the pixel.

In accordance with another aspect of the invention there is provided a computer implemented method of generating a map of the terrain in a geographic area for display on a display device, said map for display comprising a plurality of pixels, each pixel being representative of a portion of the geographic area, the method comprising:

accessing digital terrain data for the geographic area stored in at least one memory, the digital terrain data comprising a plurality of elevation values, each elevation value representing the height of the terrain at a plurality of different locations in the geographic area, and determining, for each of a plurality of pixels, an elevation value from the digital terrain data for the portion of the geographic area represented by the pixel;

accessing parameter data for the geographic area stored in the at least one memory, the parameter data comprising a plurality of parameters, each parameter being indicative of a property of a location in the geographic area different from the elevation value, and determining, for each of the plurality of pixels, at least one parameter from the parameter data for the portion of the geographic area represented by the pixel;

using the elevation value and the at least one parameter, for each of the plurality of pixels, to select a colour for the pixel from one or more predetermined texture files stored in the at least one memory; and

using the digital terrain data to determine, for each of the plurality of pixels, a normal to the terrain of the geographic area represented by the pixel, and using the determined normal and a determined direction of sunlight, for each of the plurality of pixels, to determine a shading for the pixel; and

generating the map for display on the display device by applying the selected colour and determined shading to each of the plurality of pixels.

In accordance with another aspect of the invention there is provided an apparatus for generating a map of the terrain in a geographic area for display on a display device, said map for display comprising a plurality of pixels, each pixel being representative of a portion of the geographic area, the apparatus comprising at least one processor and at least one memory storing a computer program comprising computer program code that, when executed by the at least one processor, causes the apparatus to: access digital terrain data for the geographic area stored in the at least one memory, the digital terrain data comprising a plurality of elevation values, each elevation value representing the height of the terrain at a plurality of different locations in the geographic area, and determining, for each of a plurality of pixels, an elevation value from the digital terrain data for the portion of the geographic area represented by the pixel;

access parameter data for the geographic area stored in the at least one memory, the parameter data comprising a plurality of parameters, each parameter being indicative of a property of a location in the geographic area different from the elevation value, and determining, for each of the plurality of pixels, at least one parameter from the parameter data for the portion of the geographic area represented by the pixel;

use the elevation value and the at least one parameter, for each of the plurality of pixels, to select a colour for the pixel from one or more predetermined texture files stored in the at least one memory; and use the digital terrain data to determine, for each of the plurality of pixels, a normal to the terrain of the geographic area represented by the pixel, and use the determined normal and a determined direction of sunlight, for each of the plurality of pixels, to determine a shading for the pixel; and generate the map for display on the display device by applying the selected colour and determined shading to each of the plurality of pixels.

Any of the methods in accordance with the present invention may be implemented at least partially using software, e.g. computer programs. The present invention thus also extends to a computer program comprising computer readable instructions executable to perform, or to cause a navigation device and/or server to perform, a method according to any of the aspects or embodiments of the invention.

The invention correspondingly extends to a computer software carrier comprising such software which, when used to operate a system or apparatus comprising data processing means causes, in conjunction with said data processing means, said apparatus or system to carry out the steps of the methods of the present invention. Such a computer software carrier could be a non-transitory physical storage medium such as a ROM chip, CD ROM or disk, or could be a signal such as an electronic signal over wires, an optical signal or a radio signal such as to a satellite or the like. The present invention provides a machine readable medium containing instructions which when read by a machine cause the machine to operate according to the method of any of the aspects or embodiments of the invention.

Regardless of its implementation, a client device, such as a navigation device, used in accordance with the present invention may comprise a processor, memory, and digital 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. One or more additional software programs may be provided to enable the functionality of the apparatus to be controlled, and to provide various other functions. The device preferably includes GPS (Global Positioning System) signal reception and processing functionality. The device may comprise one or more output interfaces by means of which information may be relayed to the user. The output interface(s) may include a speaker for audible output in addition to the visual display. The device may comprise input interfaces including one or more physical buttons to control on/off operation or other features of the device.

In other embodiments, the navigation device may be implemented at least in part by means of an application of a processing device which does not form part of a specific navigation device. For example the invention may be implemented using a suitable computer system arranged to execute navigation software. The system may be a mobile or portable computer system, e.g. a mobile telephone or laptop, or may be a desktop system.

Where not explicitly stated, it will be appreciated that the invention in any of its aspects may include any or all of the features desc bed in respect of other aspects or embodiments of the invention to the extent they are not mutually exclusive. In particular, while various embodiments of operations have been desc bed which may be performed in the method and by the apparatus, it will be appreciated that any one or more or all of these operations may be performed in the method and by the apparatus, in any combination, as desired, and as appropriate.

Advantages of these embodiments are set out hereafter, and further details and features of each of these embodiments are defined in the accompanying dependent claims and elsewhere in the following detailed description. Brief Description of the Drawings

For a better understanding of various examples that are useful for understanding the brief description, reference will now be made by way of example only to the accompanying drawings in which:

Figure 1 illustrates a schematic of a first apparatus in the form of a chip or a chipset;

Figure 2 illustrates a schematic of a second apparatus in the form of a computing device;

Figure 3 illustrates a flow chart of a method according to a first embodiment;

Figure 4 illustrates a flow chart of a method according to a second embodiment;

Figure 5 illustrates a schematic of a texture file; and

Figure 6 illustrates a two-dimensional (2D) map coloured and shaded according to an embodiment of the present invention.

Detailed description of the Figures

Example embodiments of the invention provide a method, an apparatus and a computer program for efficiently generating at least a portion of a map. The generated map may, for example, visualise elevation and environmental information.

Figure 1 illustrates a first apparatus 10 that may be a chip or a chipset. The first apparatus 10 comp ses one or more processors 12 (in the form of processing circuitry) and memory 14 (in the form of memory circuitry). The one or more processors 12 may include a central processing unit (CPU) and/or a graphics processing unit (GPU). A single processor 12 and a single memory 14 are shown in Figure 1 and referred to below merely for illustrative purposes.

Although the memory 14 is illustrated as a single component, it may be implemented as one or more separate components, some of which may be integrated and/or removable.

The processor 12 is configured to read from and write to the memory 14. The processor 12 may comprise an output interface via which data and/or commands are output by the processor 12 and an input interface via which data and/or commands are input to the processor 12.

The first apparatus 10 illustrated in Figure 1 may form part of a second apparatus 20. The second apparatus 20 may be integrated into a computing device, such as that illustrated in Figure 2. The computing device 20 may, for example, be a hand portable computing device such as a hand portable satellite navigation device, a mobile telephone or a tablet computer.

The memory 14 stores a computer program 16 which comp ses computer program

instructions/code 18 that control computing device 20 illustrated in Figure 2 when loaded into the processor 12. The processor 12, by reading the memory 14, is able to load and execute the computer program code 18. The computer program code 18 provides the logic and routines that enable the processor 12 to perform the methods illustrated in Figures 3 and 4. In this regard, the processor 12 and the computer program code 18 provide means for performing the methods illustrated in Figures 3 and 4 and deschbed below.

The memory 14 illustrated in Figures 1 and 2 is shown storing digital terrain data 1 1 , parameters 13, one or more predetermined texture files 15 and, optionally, sunlight information 17. The digital terrain data 1 1 , the parameters 13, the one or more texture files 15 and the sunlight information 17 are deschbed in further detail below. ln the example illustrated in Figure 2, in addition to the processor 12 and the memory 14, the computing device 20 illustrated in Figure 2 further comprises a display 21 , user input circuitry 22, one or more transceivers 24, positioning circuitry 26 and an external housing 27. In this example, the external housing 27 houses the display 21 , the user input circuitry 22, the one or more transceivers 24 and the positioning circuitry 26. In other examples, one or more of the user input circuitry 22, the display 21 , the transceivers 24 and positioning circuitry 26 might not be present in the computing device 20.

The display 21 is configured to display information under the control of the processor 12. The display 21 comprises an array of controllable pixels that may be arranged in columns and rows. The display 21 may comprise any type of display technology, e.g. a liquid crystal display (LCD), an organic light emitting diode (OLED) display, etc.

The user input circuitry 22 is configured to provide inputs to the processor 12 in response to inputs provided by a user. The user input circuitry 22 may, for example, comprise one or more keys. In some examples, some or all of the user input circuitry 22 may be integrated into the display 21 as a touch sensitive display 23. The touch sensitive display 23 may comprise any type of touch sensing technology, e.g. capacitive, resistive, etc.

The processor 12 is configured to provide data to the one or more transceivers 24 for transmission and to receive inputs from the one or more transceivers 24. The one or more transceivers 24 may include, for example, one or more wired transceivers or one or more wireless transceivers. The one or more wired transceivers may include, for instance, a Universal Serial Bus (USB) transceiver. The one or more wireless transceivers may be configured to transmit and receive radio frequency signals. For instance, the one or more wireless transceivers might be compatible with one or more short range radio protocols, such as Bluetooth or Wi-Fi protocols. Alternatively or additionally, the one or more wireless transceivers may be compatible with one or more longer range radio protocols, such as one or more cellular telephone protocols.

The positioning circuitry 26 is configured to determine the position of the computing device 20 and to provide inputs to the processor 12 indicating the position of the computing device 20. The positioning circuitry 26 may, for example, comprise satellite positioning circuitry, i.e. that uses signals received from satellites to determine the position of the computing device 20. The satellite positioning circuitry may operate, for example, in accordance with one, some or all of the following satellite positioning systems: GPS, GLONASS, Beidou and Galileo. Alternatively or additionally, the positioning circuitry 26 may be configured to position the computing device 20 using terrestrial radio signals rather than satellite signals. The radio frequency signals may be long range signals (such as cellular telephone signals) or short range signals (such as Bluetooth or Wi-Fi signals). In this regard, the positioning circuitry 26 may share some or all of its circuitry with the one or more transceivers 24.

The elements 12, 14, 21 , 22, 24 and 26 are operationally coupled and any number or combination of intervening elements can exist between them (including no intervening elements).

Figure 3 illustrates a flowchart of a method for generating at least a part of a map in real-time at the computing device 20 for display on the display 21 of the computing device 20.

The method preferably relates to generating one or more terrain portions of the map, e.g. such that the map can be used for land navigation, e.g. in the provision of navigation along a navigable, e.g. road, network. Any water portions of the map (representing sea, rivers or lakes, for example) and any infrastructure portions of the map are typically generated using a separate process from that illustrated in Figure 3. For example, the water portions of the map can simply be coloured using a single colour. It will be appreciated, however, that the method can be used in other embodiments to generate one or more water portions of the map, e.g. such that the map can be used in situations, e.g. for aquatic navigation, where the terrain and elevation of the sea bed is desired to be visualised.

The generated map or part of a map is a two dimensional (2D) view in which an image is generated as though from a camera positioned at an elevated position, in the z-direction, and with a pitch angle of 0° so as to show a bird's eye view of the area, e.g. around a current position of the computing device 20. In other words, the generated map or part of a map is a two dimensional (2D) bird's eye view.

An example of a map generated in accordance with the present invention, e.g. using the method of Figure 3, is shown in Figure 6. The map 900 shows an portion of the European continent with a planned route 901 to a destination in the vicinity of the city of Lyon (denoted by the icon 902). In this view, the camera may move in the x-y plane (i.e. the plane perpendicular to the z-axis and thus parallel to the surface on which the device is moving), e.g. so as to track the movements of the device along the route, or based on a request to pan the map.

As mentioned above, the memory 14 stores digital terrain data 1 1 , parameters 13 and one or more predetermined texture files 15. The processor 12 may cause the transceiver 24 to retrieve the digital terrain data 1 1 and the parameters 13 for a particular geographic area from a remote location (such as a remote server). The geographic area for which digital terrain data 1 1 and the parameters 13 are retrieved may depend upon the current position of the computing device 20, as determined by the positioning circuitry 26. For example, the processor 12 may cause the transceiver 24 to retrieve the digital terrain data 1 1 and parameters 13 associated with a particular geographic area in which the computing device 20 is positioned.

The digital terrain data 11 and parameters 13 may be retrieved from a map server alongside other map information, such as infrastructure information (for example, defining a road network).

The digital terrain data 11 comprises a plurality of elevation values, each of which indicates the height of terrain at a plurality of different geographic locations. The number of elevation values that are provided for geographic locations within a geographic area depends upon the granularity of the digital terrain data 11 . The digital terrain data 1 1 can therefore also be thought of as ground surface topography data.

Each of the parameters 13 provides information about a different geographic location. The parameters 13 may comprise or consist of one or more environmental parameters that are indicative of an aspect of the environment at a geographic location. A parameter may be provided for each geographic location within a geographic area. The number of parameters 13 that are provided for geographic locations within a geographic area depends upon the granularity of the plurality of parameters 13 stored in memory 14.

In some embodiments, the environmental parameters may relate to the natural environment. Such parameters may, for example, be climatic parameters. For instance, in this regard, the parameters may comprise a thermal parameter that is indicative of a temperature of at geographic location. It may, for example, be indicative of an average temperature for a period of time such as a month (for example, the current month) or a year.

Alternatively or additionally, the environmental and/or climatic parameters may comprise a parameter that is at least partially based on precipitation. Such a parameter may, for example, be indicative of an average level of precipitation over a period of time, such as a month (for example, the current month) or a year. In some implementations, this parameter may be a moisture index parameter that is indicative of the water balance of an area which takes account of gains from precipitation and losses from evapotranspiration.

Alternatively or additionally, the environmental parameters might not relate to the natural environment or climate. For instance, the environmental parameters might be indicative of the traffic density at a geographic location.

The predetermined one or more texture files 15 define multiple colours for use in colou ng the terrain portions of a map. The texture files 15 may, for example, define one or more colour ranges for use in colou ng the terrain portions. As will be appreciated, by using one or more texture files in the colouhng process, a user or third party can dramatically vary the final generated map, i.e. the map visualisation, by changing the one or more texture files, whilst utilising the same rendering process. In other words, the method according to the present invention allows simple customisation of the map visualisation.

A user may provide input at the user input circuitry 22 which causes the processor 12 to respond by controlling the display 21 to display a map of a geographic area. The processor 12 may determine which map to display by receiving inputs from the positioning circuitry 26 which indicate the current location of the computing device 20.

In order to generate the terrain portions of the map for display on the display 21 , the processor 12 carries out the process illustrated in Figure 3 for each pixel on the display 21 that displays terrain. In this regard, at block 301 in Figure 3, the processor 12 determines an elevation value for a pixel from the digital terrain data 1 1 stored in the memory 14.

In some instances, the elevation value for the pixel may merely be retrieved from the memory 14. In other instances, however, depending upon the level of granularity of the digital terrain data 1 1 and the level of magnification of the map to be displayed, the elevation value for the pixel may be an average of elevation values stored in the memory 14 that relate to the geographic location represented by the pixel.

In block 302 in Figure 3, the processor 12 determines one or more parameters for the pixel from the parameters 13 stored in the memory 14. In this regard, the processor 12 identifies one or more parameters, from the parameters 13 stored in memory 14, which relate to the geographic location represented by the pixel.

In some instances, a particular parameter for the pixel may merely be retrieved from the memory 14. In other instances, however, depending upon the level of granularity of the parameters 13 and the level of magnification of the map to be displayed, the processor 12 may determine a parameter for the pixel by averaging a plurality of parameters (of a particular type) stored in the memory 14 which relate to the geographic location represented by the pixel. As explained above, the one or more parameters may or may not be environmental parameters and could, for example, include a thermal parameter, a moisture index parameter and/or a traffic density parameter.

At block 303 in Figure 3, the processor 12 uses at least the elevation value determined in block 301 and the one or more parameters determined in block 302 to select a colour for the pixel from multiple colours defined in the one or more predetermined texture files 15 stored in the memory 14. For example, the elevation value and the parameters determined in block 301 and 302 may be used effectively as "look up values" for looking up a colour in the one or more predetermined texture files 15, e.g. as part of a texture mapping process.

At block 304 in Figure 3, the processor 12 causes the display 21 to apply a colour to the pixel using the colour selected from the one or more predetermined texture files 15, e.g. as part of the rendering process to generate the visualisation of the map data. The colour that is applied to the pixel may be the same as that which is selected from the one or more predetermined texture files 15.

Alternatively, the selected colour may be modified using a shading technique and the modified colour may be applied to the pixel.

Use of an elevation value and one or more parameters to identify a particular colour in one or more predetermined texture files 15 for use in colouring a pixel enables a combination of elevation and other information to be conveyed to a user through colour.

For example, if the one or more parameters include a parameter that is indicative of a temperature at the geographic location represented by a pixel, the colour of the pixel representing the geographic location will depend upon both the elevation at the geographic location and the temperature at the geographic location. If, for example, the one or more parameters also comprise a parameter at least partially based on precipitation, the colour of the pixel representing the geographic location will also depend upon the level of precipitation at the geographic location.

The parameters which are used to determine the colour of the terrain portions of the map may vary in dependence upon a time of year, for example. For instance, they may vary from month to month or season to season to provide a 'current' average temperature or moisture index.

It will be appreciated from reading the above that embodiments of the invention enable information for a geographic location, such as elevation and climatic information, to be combined effectively in real-time and conveyed to a user in an easily digestible manner through the colouration of a pixel relating to that geographical location.

Furthermore, in embodiments of the invention, only a limited amount of storage space need be used since the map is generated in real-time (rather than by, for example, using pre-rendered map tiles).

Embodiments of the invention may be particularly suitable for portable (or mobile) electronic device, which typically have limited processing power and storage space relative to "fixed devices" such as desktop computers and remote servers. However, it should be appreciated that the embodiments of the invention could instead be implemented using a fixed device such as a desktop computer or a remote server. Figure 4 illustrates a method according to a second embodiment of the invention. The second method also relates to generating one or more terrain portions of the map and incorporates the first method illustrated in Figure 3.

In this method, two types of parameters are processed for a pixel in addition to an elevation value: a thermal parameter and a moisture index parameter. However, in other examples, more or fewer types of parameter may be processed and/or different types of parameter may be processed, such as a traffic density parameter.

Block 501 in Figure 4 (illustrating the second method) is similar to block 302 in Figure 3 (illustrating the first method) in that the processor 12 determines an elevation value for a pixel from the digital terrain data 1 1 stored in the memory 14.

Blocks 601 and 602 in Figure 4 are similar to block 301 in Figure 3 in that the processor 12 determines one or more parameters for the pixel. As explained above, in this particular example of the second method, the one or more parameters are a thermal parameter and a moisture index parameter.

Block 701 in Figure 4 is similar to block 303 in Figure 3 in that the processor 12 uses the elevation value and the parameter(s) (in this case, determined in blocks 501 , 601 and 602 in Figure 4) to select a colour for the pixel from one or more of the predetermined texture files 15 stored in the memory 14.

Figure 5 illustrates an example of a schematic of a texture file 15. The illustrated texture file 15 includes 4 blocks, which are labelled "block 1 ", "block 2", "block 3" and "block 4" in Figure 5, although any number of blocks can be used as desired. In this example, each of the blocks comprises 32 sub-blocks, with each sub-block representing a different colour. The sub-blocks therefore represent texels (or texture pixels) of the texture file.

Figure 5 also illustrates two dimensional Cartesian coordinate axes 30, including an x-axis and a y-axis. In some implementations, one of the parameters, such as the thermal parameter, may indicate to the processor 12 which of the blocks it should select the texture from. The processor 12 may determine an x-axis value from the other parameter, such as the moisture index parameter, for use in selecting a sub-block from within a block. The processor 12 may determine a y-axis value from the elevation value, for selecting a sub-block from within a block. Thus, using the elevation value determined in block 501 in Figure 4 and the parameters determined in blocks 601 and 602 in Figure 4, the processor 12 can identify and select a sub-block from within the texture file and thus a colour for use in applying a colour to the pixel. As will be appreciated, any known texture interpolation techniques can be used when selecting the colour to be applied from the texture file.

It will be appreciated by those skilled in the art that, in other examples, each of the blocks in the texture file illustrated in Figure 5 could be a separate texture file. It will also be appreciated that a texture file may comprise more or fewer blocks than those illustrated in Figure 5, and each of the blocks may comprise more or fewer sub-blocks than those illustrated in Figure 5.

Blocks 801 and 901 in Figure 4 are similar to block 304 in Figure 3 in that the processor 12 causes a colour to be applied to the pixel using the selected colour. In the method, shading is applied to the colour selected from the one or more predetermined texture files 15 before a colour is applied to the pixel on the display 21. The colour that is applied to the pixel is not the same as the colour that is selected from the one or more predetermined texture files 15.

In more detail, at block 401 in Figure 4, the processor 12 determines a terrain normal for the pixel from the digital terrain data 11 stored in the memory 14. A terrain normal is a vector which defines an approximate angle of a surface of the real-life geographic location represented at the pixel. Then, at block 402 in Figure 4, the processor 12 determines a direction of sunlight for the pixel from the sunlight information 17 stored in the memory 14. At block 403 in Figure 4, the processor 12 combines the terrain normal determined in block 401 and the direction of sunlight determined in block 402 to determine shading for the pixel.

The direction of sunlight may, for example, be represented by one or more vectors in the stored sunlight information 17. In some embodiments of the invention, the direction of sunlight is static. That is, each time the map is displayed, the direction of sunlight does not change. Alternatively, in other embodiments, the direction of sunlight may be variable. For example, the direction of sunlight may depend upon the current time of day when the map is displayed on the display 21 .

At block 801 in Figure 4, the processor 12 modifies the colour selected from the one or more predetermined texture files 15 in block 701 using the shading determined in block 403. The processor 12 then causes the modified colour to be applied to the pixel, i.e. the pixel is rendered using the selected colour.

Any references to a "processor" or a "computer" above should be understood to encompass computers having different architectures including single- or multi-processor architectures, and also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to a computer program, instructions, code, etc should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, a gate array or a programmable logic device, etc.

The blocks illustrated in Figures 3 and 4 may represent steps in a method and/or sections of code in the computer program 16. The illustration of a particular order to the blocks does not necessa ly imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to va ous examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. For example, the same texture file 15 (or set of texture files) need not be used to generate the terrain portion(s) of a map each time the map is generated. Different texture files may be used (for example, as determined by one or more user settings) to change the colour range(s) used to generate the terrain portion(s) of the map. For example, one texture file be used to produce predominately green terrain. Alternatively, another texture file may be used to produce predominately yellow terrain. As a further alternative, a different texture file could be used to produce predominately red terrain, for instance. Where not explicitly stated, it will be appreciated that the invention in any of its aspects may include any or all of the features desc bed in respect of other aspects or embodiments of the invention to the extent they are not mutually exclusive. In particular, while various embodiments of operations have been desc bed which may be performed in the method and by the apparatus, it will be appreciated that any one or more or all of these operations may be performed in the method and by the apparatus, in any combination, as desired, and as appropriate.

Claims

CLAIMS:

1. A computer implemented method of generating a map of the terrain in a geographic area for display on a display device, said map for display comp sing a plurality of pixels, each pixel being representative of a portion of the geographic area, the method comphsing:

accessing digital terrain data for the geographic area stored in at least one memory, the digital terrain data comphsing a plurality of elevation values, each elevation value representing the height of the terrain at a plurality of different locations in the geographic area, and determining, for each of a plurality of pixels, an elevation value from the digital terrain data for the portion of the geographic area represented by the pixel;

accessing parameter data for the geographic area stored in the at least one memory, the parameter data comphsing a plurality of parameters, each parameter being indicative of a property of a location in the geographic area different from the elevation value, and determining, for each of the plurality of pixels, at least one parameter from the parameter data for the portion of the geographic area represented by the pixel;

2. The method as claimed in claim 1 , wherein the parameter data comprises a plurality of parameters, each parameter being indicative of property of the environment, optionally the natural environment, of a location in the geographic area.

3. The method as claimed in claim 2, wherein the property of the environment comprises a thermal property and/or a precipitation property of the location in the geographic area.

4. The method as claimed in any preceding claim, further comphsing accessing digital map data for the geographic area stored in at least one memory, the digital map data comphsing information indicative of infrastructure in the geographic area, optionally a road network, and wherein generating the map for display on the display device comprises providing a representation of the infrastructure using the digital map data.

5. The method as claimed in any preceding claim, wherein the direction of sunlight is static.

6. The method as claimed in any one of claims 1 to 4, wherein the direction of sunlight is variable, and the direction of sunlight is determined using sunlight information stored in the at least one memory based on the current time of day and a geographic location of the pixel.

7. The method as claimed in any preceding claim, comprising displaying the generated map on the display device.

8. An apparatus for generating a map of the terrain in a geographic area for display on a display device, said map for display comprising a plurality of pixels, each pixel being representative of a portion of the geographic area, the apparatus comprising at least one processor and at least one memory storing a computer program comprising computer program code that, when executed by the at least one processor, causes the apparatus to:

access digital terrain data for the geographic area stored in the at least one memory, the digital terrain data comprising a plurality of elevation values, each elevation value representing the height of the terrain at a plurality of different locations in the geographic area, and determining, for each of a plurality of pixels, an elevation value from the digital terrain data for the portion of the geographic area represented by the pixel;

use the elevation value and the at least one parameter, for each of the plurality of pixels, to select a colour for the pixel from one or more predetermined texture files stored in the at least one memory; and use the digital terrain data to determine, for each of the plurality of pixels, a normal to the terrain of the geographic area represented by the pixel, and use the determined normal and a determined direction of sunlight, for each of the plurality of pixels, to determine a shading for the pixel; and

generate the map for display on the display device by applying the selected colour and determined shading to each of the plurality of pixels.

9. The apparatus as claimed in claim 8, wherein the parameter data comprises a plurality of parameters, each parameter being indicative of property of the environment, optionally the natural environment, of a location in the geographic area.

10. The apparatus as claimed in claim 8 or 9, wherein the direction of sunlight is static.

1 1. The apparatus as claimed in claim 8 or 9, wherein the direction of sunlight is variable, and the direction of sunlight is determined using sunlight information stored in the at least one memory based on the current time of day and a geographic location of the pixel.

12. The apparatus as claimed in any one of claims 8 to 1 1 , further comprising a display device, and wherein the computer program code, when executed by the at least one processor, further causes the apparatus to display the generated map on the display device.

13. The apparatus as claimed in any one of claims 8 to 12, wherein the apparatus comprises a navigation device, optionally a portable navigation device or a navigation device integrated into a vehicle.

14. A computer program comprising computer program code that, when executed by at least one processor of an apparatus, causes the apparatus to perform the method as claimed in any one of claims 1 to 7.

15. A non-transitory computer readable medium storing a computer program comprising computer program code that, when executed by at least one processor of an apparatus, causes the apparatus to perform the method as claimed in any one of claims 1 to 7.