CN115098615A

CN115098615A - Map data production method and device and electronic equipment

Info

Publication number: CN115098615A
Application number: CN202210864598.3A
Authority: CN
Inventors: 陈文悦; 周燕子; 张志越
Original assignee: Beijing Baidu Netcom Science and Technology Co Ltd
Current assignee: Beijing Baidu Netcom Science and Technology Co Ltd
Priority date: 2022-07-21
Filing date: 2022-07-21
Publication date: 2022-09-23

Abstract

The disclosure provides a map data production method, a map data production device and electronic equipment, and relates to the technical field of data processing, in particular to the technical field of maps. The specific implementation scheme is as follows: acquiring M first map data produced in a first link and a first production level of each first map data, wherein the first production level is determined based on the navigation flux of a target road corresponding to the first map data, and M is a positive integer; based on the first production level, the M first map data streams are transferred to a second link from high to low for map data production; wherein the first link and the second link are both production links of map data.

Description

Map data production method and device and electronic equipment

Technical Field

The present disclosure relates to the field of data processing technologies, and in particular, to a map data production method, an apparatus, and an electronic device.

Background

Along with the construction and development of cities, the real world changes all the time, and if the change of the real world cannot be updated to a map in time, users can be guided by mistake, and the situations of destination unreachability, detour, violation of regulations and the like are generated.

At present, map data production processes mainly include production after actual collection, including production links such as collection, identification, data preprocessing, change discovery, change production, fusion, data distribution and the like, and map data production is performed according to the arrival time sequence of map data.

Disclosure of Invention

The disclosure provides a map data production method and device and electronic equipment.

According to a first aspect of the present disclosure, there is provided a map data production method including:

acquiring M first map data produced in a first link and a first production level of each first map data, wherein the first production level is determined based on the navigation flux of a target road corresponding to the first map data, and M is a positive integer;

based on the first production grade, the M first map data streams are transferred to a second link from high to low for map data production;

wherein the first link and the second link are production links of map data.

According to a second aspect of the present disclosure, there is provided a map data producing apparatus including:

the first obtaining module is used for obtaining M first map data obtained in a first link and a first production grade of each first map data, wherein the first production grade is determined based on the navigation flux of a target road corresponding to the first map data, and M is a positive integer;

the first flow module is used for transferring the M first map data flows to a second link from high to low to produce map data based on the first production grade;

wherein the first link and the second link are production links of map data.

According to a third aspect of the present disclosure, there is provided an electronic device comprising:

at least one processor; and

a memory communicatively coupled to the at least one processor; wherein the content of the first and second substances,

the memory stores instructions executable by the at least one processor to enable the at least one processor to perform any one of the methods of the first aspect.

According to a fourth aspect of the present disclosure, there is provided a non-transitory computer readable storage medium having stored thereon computer instructions for causing a computer to perform any one of the methods of the first aspect.

According to a fifth aspect of the present disclosure, there is provided a computer program product comprising a computer program which, when executed by a processor, implements any of the methods of the first aspect.

According to the technology disclosed by the invention, the problem of poorer timeliness of map data production in the related technology is solved, and the timeliness of map data production is improved.

It should be understood that the statements in this section are not intended to identify key or critical features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become apparent from the following description.

Drawings

The drawings are included to provide a better understanding of the present solution and are not to be construed as limiting the present disclosure. Wherein:

fig. 1 is a schematic flow chart of a map data production method according to a first embodiment of the present disclosure;

FIG. 2 is a schematic diagram illustrating the flow priorities of map data;

FIG. 3 is a diagram of task packages of map data;

FIG. 4 is a task diagram of map data;

FIG. 5 is one of the schematic diagrams of production monitoring for a production link;

FIG. 6 is a second schematic view of monitoring the production status of the production link;

fig. 7 is a schematic configuration diagram of a map data production apparatus according to a second embodiment of the present disclosure;

fig. 8 is a schematic block diagram of an example electronic device used to implement embodiments of the present disclosure.

Detailed Description

Exemplary embodiments of the present disclosure are described below with reference to the accompanying drawings, in which various details of the embodiments of the disclosure are included to assist understanding, and which are to be considered as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the present disclosure. Also, descriptions of well-known functions and constructions are omitted in the following description for clarity and conciseness.

First embodiment

As shown in fig. 1, the present disclosure provides a map data production method, including the steps of:

step S101: the method comprises the steps of obtaining M first map data obtained through production in a first link and a first production level of each first map data, wherein the first production level is determined based on navigation flux of a target road corresponding to the first map data.

Wherein M is a positive integer.

In the embodiment, the map data production method relates to the technical field of data processing, in particular to the technical field of maps, and can be widely applied to a map data production scene. The map data production method of the embodiment of the present disclosure may be executed by the map data production apparatus of the embodiment of the present disclosure. The map data production apparatus of the embodiment of the present disclosure may be configured in any electronic device to execute the map data production method of the embodiment of the present disclosure. The electronic device may be a server or a terminal device, and is not limited specifically here.

In step S101, the first link may be a first link in a production link of the map data, or may be a subsequent link in the production link, which is not specifically limited herein. The first link of the map data can be data acquisition, namely acquiring map data to produce the map data.

Under the condition that the first link is the first link in the map data production link, the first map data sent by other electronic equipment can be received, and the first map data can be acquired by other electronic equipment, such as acquisition through an acquisition vehicle, a camera, point cloud equipment and the like. Accordingly, the first production level of each first map data may be determined based on the navigation flux of the target road to which the first map data corresponds.

The target road corresponding to the first map data may refer to a road indicated by the image content in the first map data, and the navigation flux of the target road may refer to the number of target navigation routes requested by the user for the map data, where the target navigation routes are navigation routes passing through the target road.

In an alternative embodiment, the navigation flux of the target road is proportional to the first production level, i.e. the larger the navigation flux, the higher the first production level.

In the case that the first link is not the first link in the map data production link, the first map data may be obtained by receiving the map data of the previous link of the first link and producing the first map data based on the map data, for example, by identifying (or discovering changes, making changes, etc.) the map data circulated in the previous link. Accordingly, the production level corresponding to the map data of the previous link may be determined as the first production level of the first map data.

Step S102: and based on the first production grade, the M first map data streams are transferred to a second ring section from high to low for map data production.

Wherein the first link and the second link are production links of map data.

In this step, the second link is a link subsequent to the first link, a data channel may be established between the first link and the second link to transfer the map data, and when the first link obtains the first map data, the M first map data may be transferred to the second link in order from high to low to produce the map data based on the first production level.

As shown in fig. 2, the map data are transferred in the order of the first production level from high to low, that is, the map data with the first production level are transferred first, and the map data with the first production level are transferred later.

Accordingly, the second link may perform map data production such as recognition, data preprocessing, change discovery, and the like in the order of the inflow of the first map data.

In the embodiment, M pieces of first map data obtained by production in a first link and a first production level of each piece of first map data are obtained, where the first production level is determined based on a navigation flux of a target road corresponding to the first map data; and based on the first production level, the M first map data streams are transferred to a second link from high to low for map data production. Therefore, the production priority of the map data can be divided according to the influence degree of the road on the user, and data circulation is performed between production links of the map data according to the production priority of the map data, so that the map data with high production priority is preferentially produced, and the timeliness of the map data production is improved.

In an alternative embodiment, the first link is an intermediate link in the production of map data. Optionally, before step S101, the method further includes:

acquiring M pieces of second map data acquired in a third link, wherein the second map data comprise image contents of the target road;

determining a second production level of the second map material based on the navigation flux of the target road;

based on the second production level, the M second map data are transferred to the first link from high to low to produce map data;

the step S101 specifically includes:

and acquiring M first map data produced by the first link based on the M second map data, and determining the second production level as the first production level.

In this embodiment, the third link is a first link in the map data production link, that is, a data acquisition link, and may receive second map data sent by other electronic devices, where the second map data may be acquired by other electronic devices, for example, by acquiring a vehicle, a camera, a point cloud device, and the like.

The first map data and the second map data are both associated with the same target road, and a second production level of the second map data may be determined based on the navigation traffic of the target road. The second production level can be determined based on the navigation flux, the second production level is in a direct proportion relation with the navigation flux, and the navigation flux can be used as a reference influence factor, and the second production level can be determined by combining the data source, the resource availability degree and the data confidence determined by the data type.

The M second map data streams are transferred to the first link for map data production in the order from high to low based on the second production level, and the transfer mode is similar to the transfer mode for map data production in the order from high to low based on the first production level, and is not repeated here.

Correspondingly, the first link can perform map data production on the second map data flowing in, such as data identification, to obtain M first map data, and determine the second production level as the first production level, so that the production links of the map data can be coupled through the production priority determined by the navigation flux of the target road associated with the map data, the production priority is guaranteed, namely the priority circulation of important data, and the timeliness of the map data production is improved.

Optionally, the determining a second production level of the second map material based on the navigation throughput of the target road includes:

acquiring first target information, wherein the first target information comprises at least one of a data source, a data type and a data availability degree;

determining the confidence of the second map data based on the first target information;

and carrying out weighting processing on the navigation flux and the confidence coefficient to obtain the second production level.

In this embodiment, the navigation flux may be used as a reference influence factor, and the second production level may be determined by using the data confidence determined by the data source, the resource availability, and the data type as a secondary influence factor.

Specifically, the first target information may be obtained, where the first target information may include at least one of a data source, a data type, and a data availability degree, the data source may indicate a data source, such as map data collected by an operating vehicle, map data collected by a camera, and the like, the data type may indicate a data type, such as an image, a video, and the like, and the data availability degree may indicate data quality, such as an image definition, and the like. The first target information may be determined based on a type of the electronic device used for acquiring the second map data, for example, the electronic device acquiring the second map data is a point cloud device, and the second map data may be determined to be a point cloud image with high image definition.

The confidence coefficient of the second map data can be obtained by weighting according to the data source, the data type and the data availability degree, the confidence coefficient is used as a secondary influence factor, the navigation flux is used as a reference influence factor, the two are weighted to obtain a second production level, and the accuracy and the timeliness of map data production are improved.

Optionally, the step S102 specifically includes:

determining the data amount of task scheduling based on the first production grade, wherein the data amount is in an inverse relation with the first production grade;

and based on the first production level, transferring task packages to the second link to produce the map data in a descending order, wherein the task packages are obtained by packaging the M first map data according to the data volume.

In this embodiment, when data circulation is performed based on the production priority of the map data, task scheduling may be further performed according to the production priority, and the data amount of the task scheduling may be determined according to the first production level, where the data amount and the first production level have an inverse relationship, that is, the higher the first production level is, the smaller the data amount of the task scheduling may be.

Under the condition that the first production level is high, the task packet is distributed by reducing the task circulation granularity, so that the packaging time can be shortened.

As shown in fig. 3, in the related art, generally, if a task satisfies a certain data amount, the task is scheduled to distribute map data (as shown in the left diagram in fig. 3), but in the present embodiment, the map data of a high production level may be extracted, and instead of waiting for a group of tasks, the map data may be directly scheduled and issued to the second link as a single task to perform production operations (as shown in the right diagram in fig. 3), so as to shorten the waiting time of high-quality data, and further improve the timeliness of map data production.

Optionally, the method further includes:

interrupting map data production at the second link for a second task package if a first task package is received at the second link to perform map data production at the second link for the first task package;

the first task package is obtained from a map data package of which the first production level is greater than a first preset threshold value in the M first map data.

In this embodiment, the first preset threshold may be set according to an actual situation, and when the first production level is greater than the first preset threshold, the first map data is represented as high-quality data, map data production may be preferentially performed, and correspondingly, the first task package obtained by grouping the first map data is a task package of a high-quality task.

The high-priority tasks can be set on the top, and preemptive operation can be performed, so that the fastest circulation is guaranteed. As shown in fig. 4, in the related art, generally, a streaming job is performed, and when a high-priority task a flows in, it is necessary to wait for existing tasks B and C (shown in the left diagram of fig. 4) to be completed, and then a map data production task of the task a is performed. In the embodiment, when a new task a is added to the task queue, priority determination may be performed, and if the new task a is a high-priority task, the existing task is interrupted, and an insertion operation (as shown in the right diagram in fig. 4) is performed, so that the waiting time for high-priority data production is further shortened, and the timeliness of map data production is improved.

Optionally, the method further includes:

and storing target map data under the condition that the data volume of the map data flowing into the second link is larger than a second preset threshold, wherein the target map data is the map data of which the first production grade is smaller than a third preset threshold in the M first map data.

In this embodiment, the map data can be cached according to the production capacity and dynamically allocated.

The second preset threshold value can be set according to actual conditions, and when the data volume of the map data flowing into the second link is larger than the second preset threshold value, the map data backlog exists at the second link, and the production capacity cannot be guaranteed to be processed in time. The map data (i.e., the map data representing the non-important road area and the low confidence coefficient) with the first production level smaller than the third preset threshold among the M first map data can be stored, and the ex-warehouse operation is performed when the capacity is rich, so that the data quality is supplemented, and therefore the high-quality data is guaranteed to be processed preferentially all the time.

Optionally, the method further includes:

monitoring second target information of each production link of the map data to obtain monitoring information, wherein the monitoring information is used for indicating the map data production condition of each production link, and the second target information comprises at least one of the following items:

the data volume of the inflow map data, the consumption condition of the map data, the production standard reaching rate of the map data in the preset time and the time consumption condition of the map data production.

In the embodiment, at least one of the data amount of the map data flowing into each production link of the map data, the consumption condition of the map data, the production standard reaching rate of the map data in the preset time and the time consumption condition of the map data production can be monitored so as to quickly identify the problems of data empty production and overstock.

As shown in fig. 5, for example, for monitoring a production link, the monitoring content may include: the input amount of map data (as shown by the column bar in fig. 5), the percentage of burnout of each process (including plan creation, operation, quality inspection, acceptance, etc.) in the production link to the map data, i.e., the consumption of the data (as shown by the curve in fig. 5).

And (3) establishing an aging measurement index of the production link by combining the priority of map data and the productivity and stability of each production link, wherein the aging measurement index comprises time T + minute level, T +1, T +2, T +3, T +7 and the like. And monitoring the time efficiency standard-reaching rate and time consumption of each production link, and as shown in fig. 6, performing overrun early warning, supporting quick positioning to a problem link, and finding and solving a system stuck point.

Second embodiment

As shown in fig. 7, the present disclosure provides a map data production apparatus 700, including:

a first obtaining module 701, configured to obtain M first map data obtained in a first link and a first production level of each first map data, where the first production level is determined based on a navigation flux of a target road corresponding to the first map data, and M is a positive integer;

a first forwarding module 702, configured to forward, based on the first production level, the M first map data streams to a second link in order from top to bottom for map data production;

wherein the first link and the second link are production links of map data.

Optionally, the apparatus further comprises:

the second acquisition module is used for acquiring M second map data acquired in a third link, and the second map data comprise the image content of the target road;

a determination module for determining a second production level of the second map material based on the navigation flux of the target road;

the second circulation module is used for circulating the M second map data to the first link from high to low to produce the map data based on the second production level;

the first obtaining module 701 is specifically configured to obtain M first map data that are obtained by the first link based on the M second map data, and determine the second production level as the first production level.

Optionally, the determining module is specifically configured to:

and weighting the navigation flux and the confidence coefficient to obtain the second production level.

Optionally, the first circulation module 702 is specifically configured to:

and based on the first production level, task packages are circulated to the second link from high to low to produce the map data, and the task packages are obtained by packaging the M first map data according to the data volume.

Optionally, the apparatus further comprises:

the system comprises an interruption module, a data processing module and a data processing module, wherein the interruption module is used for interrupting map data production aiming at a second task packet at a second link under the condition that the first task packet is received at the second link so as to carry out map data production aiming at the first task packet at the second link;

Optionally, the apparatus further comprises:

the storage module is configured to store target map data when a data amount of the map data flowing in the second link is greater than a second preset threshold, where the target map data is a map data of which the first production level is smaller than a third preset threshold among the M first map data.

Optionally, the apparatus further comprises:

the monitoring module is used for monitoring second target information of each production link of the map data to obtain monitoring information, the monitoring information is used for indicating the map data production condition of each production link, and the second target information comprises at least one of the following items:

The map data production apparatus 700 provided by the present disclosure can implement each process implemented by the map data production method embodiment, and can achieve the same beneficial effects, and for avoiding repetition, the details are not repeated here.

In the technical scheme of the disclosure, the collection, storage, use, processing, transmission, provision, disclosure and other processing of the personal information of the related user are all in accordance with the regulations of related laws and regulations and do not violate the good customs of the public order.

The present disclosure also provides an electronic device, a readable storage medium, and a computer program product according to embodiments of the present disclosure.

FIG. 8 shows a schematic block diagram of an example electronic device that may be used to implement embodiments of the present disclosure. Electronic devices are intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The electronic device may also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions, are meant to be examples only, and are not intended to limit implementations of the disclosure described and/or claimed herein.

As shown in fig. 8, the apparatus 800 includes a computing unit 801 that can perform various appropriate actions and processes according to a computer program stored in a Read Only Memory (ROM)802 or a computer program loaded from a storage unit 808 into a Random Access Memory (RAM) 803. In the RAM 803, various programs and data required for the operation of the device 800 can also be stored. The calculation unit 801, the ROM 802, and the RAM 803 are connected to each other by a bus 804. An input/output (I/O) interface 805 is also connected to bus 804.

A number of components in the device 800 are connected to the I/O interface 805, including: an input unit 806 such as a keyboard, a mouse, or the like; an output unit 807 such as various types of displays, speakers, and the like; a storage unit 808, such as a magnetic disk, optical disk, or the like; and a communication unit 809 such as a network card, modem, wireless communication transceiver, etc. The communication unit 809 allows the device 800 to exchange information/data with other devices via a computer network such as the internet and/or various telecommunication networks.

Computing unit 801 may be a variety of general and/or special purpose processing components with processing and computing capabilities. Some examples of the computing unit 801 include, but are not limited to, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), various dedicated Artificial Intelligence (AI) computing chips, various computing units running machine learning model algorithms, a Digital Signal Processor (DSP), and any suitable processor, controller, microcontroller, and the like. The calculation unit 801 executes the respective methods and processes described above, such as the map data production method. For example, in some embodiments, the map data production method may be implemented as a computer software program tangibly embodied in a machine-readable medium, such as storage unit 808. In some embodiments, part or all of the computer program can be loaded and/or installed onto device 800 via ROM 802 and/or communications unit 809. When the computer program is loaded into the RAM 803 and executed by the computing unit 801, one or more steps of the map data production method described above may be performed. Alternatively, in other embodiments, the computing unit 801 may be configured to perform the map data production method in any other suitable manner (e.g., by means of firmware).

Various implementations of the systems and techniques described here above may be implemented in digital electronic circuitry, integrated circuitry, Field Programmable Gate Arrays (FPGAs), Application Specific Integrated Circuits (ASICs), Application Specific Standard Products (ASSPs), system on a chip (SOCs), load programmable logic devices (CPLDs), computer hardware, firmware, software, and/or combinations thereof. These various embodiments may include: implemented in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, receiving data and instructions from, and transmitting data and instructions to, a storage system, at least one input device, and at least one output device.

Program code for implementing the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowchart and/or block diagram to be performed. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of this disclosure, a machine-readable medium may be a tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a machine-readable storage medium would include an electrical connection based on one or more wires, a portable computer diskette, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

To provide for interaction with a user, the systems and techniques described here can be implemented on a computer having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to a user; and a keyboard and a pointing device (e.g., a mouse or a trackball) by which a user can provide input to the computer. Other kinds of devices may also be used to provide for interaction with a user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user may be received in any form, including acoustic, speech, or tactile input.

The systems and techniques described here can be implemented in a computing system that includes a back-end component (e.g., as a data server), or that includes a middleware component (e.g., an application server), or that includes a front-end component (e.g., a user computer having a graphical user interface or a web browser through which a user can interact with an implementation of the systems and techniques described here), or any combination of such back-end, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include: local Area Networks (LANs), Wide Area Networks (WANs), and the Internet.

The computer system may include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. The server may be a cloud server, a server of a distributed system, or a server with a combined blockchain.

It should be understood that various forms of the flows shown above may be used, with steps reordered, added, or deleted. For example, the steps described in the present disclosure may be executed in parallel or sequentially or in different orders, and are not limited herein as long as the desired results of the technical solutions disclosed in the present disclosure can be achieved.

The above detailed description should not be construed as limiting the scope of the disclosure. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may be made in accordance with design requirements and other factors. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A map data production method, comprising:

based on the first production level, the M first map data streams are transferred to a second link from high to low for map data production;

wherein the first link and the second link are production links of map data.

2. The method of claim 1, wherein prior to obtaining the M first map materials produced in the first link and the first production level of each first map material, further comprising:

acquiring M second map data acquired in a third link, wherein the second map data comprise image contents of the target road;

determining a second production level of the second map material based on the navigation throughput of the target road;

the obtaining of the M first map data produced in the first link and the first production level of each first map data includes:

3. The method of claim 2, wherein said determining a second production level of said second map material based on said target road's navigation throughput comprises:

determining a confidence level of the second map material based on the first target information;

4. The method of claim 1, wherein said shifting said M first map data streams to a second link for map data production in a high-to-low order based on said first production level comprises:

determining the data amount of task scheduling based on the first production level, wherein the data amount is in an inverse relation with the first production level;

5. The method of claim 4, further comprising:

6. The method of claim 1, further comprising:

7. The method of claim 1, further comprising:

8. A map data production apparatus comprising:

the first obtaining module is used for obtaining M first map data obtained by production in a first link and a first production level of each first map data, wherein the first production level is determined based on the navigation flux of a target road corresponding to the first map data, and M is a positive integer;

the first flow module is used for transferring the M first map data flows to a second link from high to low to produce map data based on the first production level;

wherein the first link and the second link are both production links of map data.

9. The apparatus of claim 8, further comprising:

the first obtaining module is specifically configured to obtain M first map data that are produced by the first link based on the M second map data, and determine the second production level as the first production level.

10. The apparatus according to claim 9, wherein the determining module is specifically configured to:

11. The apparatus of claim 8, wherein the first circulation module is specifically configured to:

12. The apparatus of claim 11, further comprising:

13. The apparatus of claim 8, further comprising:

14. The apparatus of claim 8, further comprising:

15. An electronic device, comprising:

at least one processor; and

the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the method of any one of claims 1-7.

16. A non-transitory computer readable storage medium having stored thereon computer instructions for causing the computer to perform the method of any one of claims 1-7.

17. A computer program product comprising a computer program which, when executed by a processor, implements the method according to any one of claims 1-7.