Method and apparatus for acquiring building height from dual-polarization SAR image
Patent Information
- Application Number
- PCT/CN2025/091659
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-02-26
- Filing Date
- 2025-04-28
- Publication Date
- 2026-09-03
Smart Images
Figure CN2025091659_03092026_PF_FP_ABST
Abstract
Description
A method and apparatus for acquiring building height from dual-polarization SAR images
[0001] This application claims priority to Chinese Patent Application No. 202510221475.1, filed on February 26, 2025, entitled "A Method and Apparatus for Obtaining Building Height from Dual-Polarization SAR Images", the entire contents of which are incorporated herein by reference. Technical Field
[0002] This application relates to the field of airborne remote sensing technology, and in particular to a method and apparatus for acquiring building heights from dual-polarization SAR images using synthetic aperture radar wide-area surveillance and measurement technology. Background Technology
[0003] Building height measurement and estimation is a crucial aspect of aerial remote sensing applications, vital for wide-area ground surveillance, regional development planning, and resource distribution estimation. Currently, common methods for obtaining building heights include: on-site measurements using instruments such as total stations, optical rangefinders, and GPS; extracting specific building heights by integrating geographic information system databases and building design drawings; and estimating ground building heights using 3D aerial imagery and photogrammetry. While these techniques offer high accuracy, they are expensive, heavily reliant on prior auxiliary data, and unsuitable for estimating the heights of widely distributed ground buildings. Accurate and reliable measurement of ground building height distribution without the need for reference information is of paramount importance for remote sensing technology.
[0004] Due to the limitations of optical remote sensing equipment in measuring the height of buildings on the Earth's surface, the reflection and scattering characteristics of electromagnetic waves can be utilized to extract building heights from microwave remote sensing imaging data. A typical approach is to generate two physically coherent images of the observation area using interferometric synthetic aperture radar (ISA), and then inversely deduce the building height by analyzing the phase difference between corresponding pixels. However, ISA imaging has strict requirements on the baseline length between antennas and the registration accuracy of the images, especially in areas with complex terrain, requiring the establishment of numerous control points as geometric correction points. Given the shortcomings of ISA, domestic and international scholars have utilized SAR image amplitude information and prior parameters to invert the backscattering characteristics of ground features, establishing a geometric optics-physical optics (GO-PO) model, and subsequently deriving formulas for calculating building heights.
[0005] At present, there are still some problems with the building height estimation method based on single SAR images that need to be solved: there are many constraints that need to be set manually, and the calculation process is complicated; it relies on prior knowledge and reference building heights, and the measurement independence is poor; the boundaries of scattering areas such as building overlap in SAR images are blurred, and it is impossible to accurately determine the geometric distance between each area; the building height is inverted from a single polarization image and prior knowledge, without comprehensively analyzing the impact of other polarization information on the height estimation, resulting in poor measurement accuracy. Summary of the Invention
[0006] This application proposes a method and apparatus for acquiring building heights from dual-polarization SAR images, which solves the problems of computational complexity and poor accuracy in existing technologies.
[0007] In a first aspect, embodiments of this application propose a method for obtaining building height from dual-polarization SAR images, comprising the following steps:
[0008] Acquire dual-polarization SAR images containing buildings using aerial remote sensing;
[0009] The location of the near-end bright line of the building image is determined based on the dual-polarization SAR image, which is taken as the first near-end horizontal position of the building along the ground.
[0010] The second horizontal position at the far end of the boundary line of the shadow area of the building image was determined based on the SAR image.
[0011] The building height is calculated based on the flight altitude, downward angle, near-end horizontal first position, and far-end horizontal second position.
[0012] In one embodiment of this application, determining the first horizontal position of the near-end bright line of a building image based on a dual-polarization SAR image specifically includes:
[0013] Fit the first centerline in the bright line region along the near end of the secondary scattering in the HH-SAR image;
[0014] In the bright line region along the near end of the secondary scattering in the VV-SAR image, fit the second center line;
[0015] The average straight line of the first centerline and the second centerline is used as the near-end edge of the building along the ground to determine the first horizontal position of the near end.
[0016] In one embodiment of this application, the far boundary line of the shadowed region is found in the HH-SAR image.
[0017] In one embodiment of this application, the distance between corner reflectors is determined based on SAR images of multiple corner reflectors preset on the ground, and the distance S0 between the near-end horizontal first position and the far-end horizontal second position is obtained.
[0018] In one embodiment of this application, the bright line region is fitted with a straight line centerline using the RANSAC algorithm.
[0019] In one embodiment of this application, the antenna downward viewing angle of the radar is set to θ. The aircraft equipped with dual-polarization SAR radar takes off and enters a predetermined flight path at an altitude of H. The flight path is greater than or equal to 3 synthetic aperture lengths and remains parallel to the azimuth direction of the building to be measured. Under standard frontal side-view conditions, the radar generates SAR images with HH and VV polarization.
[0020] Secondly, embodiments of this application also propose a dual-polarization SAR image building height acquisition device, used to implement the method described in any embodiment of the first aspect of this application, including: an acquisition module, a determination module, and a generation module.
[0021] The acquisition module is used to acquire dual-polarization SAR images containing buildings through aerial remote sensing.
[0022] The determining module is used to obtain the proximal horizontal first position and the distal horizontal second position.
[0023] The generation module is used to calculate the building height based on the flight altitude, downward viewing angle, near-end horizontal first position, and far-end horizontal second position.
[0024] Thirdly, embodiments of this application also provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in any embodiment of the first aspect of this application.
[0025] Fourthly, embodiments of this application also provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described in any embodiment of the first aspect of this application.
[0026] The above-described technical solutions adopted in the embodiments of this application can achieve the following beneficial effects:
[0027] To address the aforementioned issues, this invention proposes a building height estimation method based on dual-polarization SAR images. This method generates SAR images of the same building using both vertically polarized (VV) and horizontally polarized (HH) electromagnetic waves via synthetic aperture radar. The difference between the two polarization images is then utilized to further improve the accuracy of building height measurement.
[0028] The height of a building is calculated by using the distance between the center line of the SAR image and the shadow boundary of the dihedral angle formed by the building and the ground, and the radar downward view. This avoids the need for prior parameters such as the dielectric constant of the wall and the ground, roughness parameters, and the main length of the building, which are required in the traditional GO-PO model, making the implementation simpler.
[0029] The center line of the dihedral imaging with the highest building brightness and the boundary of the darkest shadow area in the SAR image are used as the range estimation limit. This is easy to obtain on SAR images and avoids the problem of large range estimation error caused by the blurring of the boundaries between the overlapping area and other backscattered areas when estimating the height of SAR images based on geometric optics.
[0030] Relative distances can be calculated using the distance between corner reflectors in SAR images, eliminating the need for optical maps that carry geographic coordinate information. Attached Figure Description
[0031] Figure 1 is a flowchart of an embodiment of the method for obtaining building height from dual-polarization SAR images in this application;
[0032] Figure 2(a) shows the scattering intensity of different areas of ground buildings and the corresponding SAR image distribution under strict geometric optics conditions;
[0033] Figure 2(b) is a schematic diagram of the scattering intensity of ground buildings in different areas and the corresponding SAR image distribution when the radar transmitted beam is approximately a parallel beam;
[0034] Figure 3 is a schematic diagram of ground building images in a dual-polarization SAR image;
[0035] Figure 4 is a schematic diagram of ground corner reflector images in a dual-polarization SAR image;
[0036] Figure 5 shows an embodiment of the dual-polarization SAR image building height acquisition device of this application;
[0037] Figure 6 shows another embodiment of the dual-polarization SAR image building height acquisition device of this application. Detailed Implementation
[0038] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0039] The technical solutions provided by the various embodiments of this application are described in detail below with reference to the accompanying drawings.
[0040] The building height estimation method based on dual-polarization SAR images can achieve height measurement of flat-roofed buildings without prior information. To better illustrate the above technical solutions, the following detailed description, in conjunction with the accompanying drawings, explains the technical solutions provided by various embodiments of this application.
[0041] Figure 1 is a flowchart of an embodiment of the method for obtaining building height from dual-polarization SAR images according to this application. A method for obtaining building height from dual-polarization SAR images includes the following steps:
[0042] Step 110: Obtain dual-polarization SAR images containing buildings using aerial remote sensing.
[0043] In one embodiment of this application, the antenna downward viewing angle of the radar is set to θ. The aircraft equipped with dual-polarization SAR radar takes off and enters a predetermined flight path at an altitude of H. The flight path is greater than or equal to 3 synthetic aperture lengths and remains parallel to the azimuth direction of the building to be measured. Under standard frontal side-view conditions, the radar generates SAR images with HH and VV polarization.
[0044] Step 120: Determine the position of the near-end bright line of the building image based on the dual-polarization SAR image, and use it as the first near-end horizontal position of the building along the ground.
[0045] In one embodiment of this application, determining the first horizontal position of the near-end bright line of a building image based on a dual-polarization SAR image specifically includes:
[0046] Fit the first centerline in the bright line region along the near end of the secondary scattering in the HH-SAR image;
[0047] In the bright line region along the near end of the secondary scattering in the VV-SAR image, fit the second center line;
[0048] The average straight line of the first centerline and the second centerline is used as the near-end edge of the building along the ground to determine the first horizontal position of the near end.
[0049] In one embodiment of this application, the centerline of the bright line region is fitted using the Random Sample Consensus (RANSAC) algorithm. RANSAC is applied to both bright line regions to fit the centerline, with a confidence level (p) set to 0.994 and a sample size (m) set to 4. After obtaining two fitted lines, the average of the two lines is used as the dihedral edge of the building along the ground.
[0050] Step 130: Determine the second horizontal position at the far end of the boundary line of the shadow area of the building image based on the SAR image.
[0051] In one embodiment of this application, the far boundary line of the shadowed region is found in the HH-SAR image.
[0052] Step 140: Calculate the building height based on the flight altitude, downward angle, near-end horizontal first position, and far-end horizontal second position.
[0053] In one embodiment of this application, the distance between multiple corner reflectors is determined based on SAR images from multiple corner reflectors pre-installed on the ground, and the distance S0 between a near-end horizontal first position and a far-end horizontal second position is obtained. Specifically, the calculation process is as follows: two SAR radars with a distance L are placed upwards along a distance perpendicular to the flight path. cr For corner reflectors, after the SAR radar generates an image, the number of pixels corresponding to the center point distance of the circular bright spots formed by the two corner reflectors in the SAR image is N. cr The number of pixels corresponding to the distance between the first horizontal position at the near end and the second horizontal position at the far end is N. p ,but:
[0054] Therefore, before implementing steps 110 to 140 of the embodiments of this application, corner reflectors with fixed spacing can be first deployed in an unobstructed open area near the building to be tested.
[0055] In one embodiment, the estimated height h of the building should be expressed as:
[0056] Where S0 is the distance between the first proximal horizontal position and the second distal horizontal position.
[0057] Figure 2(a) shows a schematic diagram of the scattering intensity of different areas of the ground building. In the pixel-level registered image of the two SAR images, the bright line regions along the secondary scattering side of the building in the HH-SAR and VV-SAR images are found. These bright line regions correspond to point B on the ground in Figure 2(a). Here, θ1 represents the radar downward view corresponding to point B of the building, θ1+θ2 represents the radar downward view corresponding to point A of the building, θ1+θ2+θ3 represents the radar downward view corresponding to point C of the building, P represents the position of the aircraft, H represents the flight altitude, h represents the height of the building, ABCD represents the vertical interface outline of the building, R represents the distance between the radar antenna and point B of the building, E represents the intersection of point B and the perpendicular line of the extension of PA, F represents the intersection of the arc with radius PB (length R) and the extension of PA, G represents the intersection of the extension of PC and the ground, and the color band A1-B1-D1-G1 represents the actual projection distance distribution image of each imaging point in the building on the ground. (Both HH and VV images conform); where A1 represents the intersection of the arc with P as the center and PA as the radius with the ground; B1 and D1 represent the intersections of the building with the ground (same as points B and D); G1 represents the intersection of the extended line of PC with the ground (same as point G); the color band A2-C1-B2-G2 represents the distance distribution of each imaging point in the building on the SAR image (both HH and VV images conform); where A2 represents the projection of building point A on the SAR image; C1 represents the projection of building point C on the SAR image; B2 represents the projection of building point B on the SAR image; and G2 represents the projection of the intersection point G of the extended line of PC with the ground on the SAR image. The high-brightness bright line region along the secondary scattering side of the building in the HH-SAR image and VV-SAR image is located at B2 of the color band A2-C1-B2-G2.
[0058] Figure 2(b) is a schematic diagram showing the scattering intensity of different areas of ground buildings and the corresponding SAR image distribution when the radar transmitted beam is approximately a parallel beam. In the figure, D represents secondary scattering, T represents tertiary scattering, S represents shadow, BG represents ground scattering, BR represents roof scattering, and L represents wall scattering. In the figure, θ represents the lower viewing angle, h represents the height of the building, W represents the width of the building in the lower viewing angle plane, and the color bands in the figure represent the projection distance distribution of each imaging point of the building on the SAR image. L+BR+BG, L+BG, D, T, and S represent the SAR images formed by the corresponding lower left adjacent parallel line regions (parallel lines are equidistant lines along the radar range image). In the embodiments of this application, the range of the lower viewing angle is determined to be θ < actan(h / W).
[0059] Figure 3 is a schematic diagram of ground buildings in a SAR image. The RANSAC algorithm was used to fit the centerline of each of the two bright-line regions, resulting in two fitted lines. The average of these two lines was then used as the dihedral edge of the building along the ground, as shown on the left side of Figure 3. Subsequently, in the HH-SAR image, the boundary line of the shadowed region extending towards the far end was found, as shown on the right side of Figure 3.
[0060] Figure 4 is a schematic diagram of a ground corner reflector image in a SAR image; in one embodiment, four corner reflectors are used. Preferably, they are arranged in a straight line at a set spacing, for example, near ground buildings, the corner reflector spacing is set to L0. The distance S0 between the dihedral edge and the boundary line of the shadowed area along the distance to the far end can be calculated based on the distance of the corner reflectors (as shown in Figure 4).
[0061] It should be noted that the execution subject of each step of the method provided in this application embodiment can be the same device, or the method can be executed by different devices. For example, the execution subject of steps 110 and 120 can be device 1, and the execution subject of step 130 can be device 2; or the execution subject of step 110 can be device 1, and the execution subject of steps 120 and 130 can be device 2; and so on.
[0062] Figure 5 illustrates an embodiment of the dual-polarization SAR image building height acquisition device of this application, used to implement the method described in any embodiment of the first aspect of this application, including: acquisition module 510, determination module 520, and generation module 530.
[0063] The acquisition module is used to acquire dual-polarization SAR images containing buildings through airborne remote sensing. For example, an aircraft equipped with a dual-polarization SAR radar flies along a specific straight flight path at an altitude of H, with the SAR radar's downward viewing angle at θ, generating two SAR images with HH and VV polarizations. Preferably, the flight path of the aircraft equipped with the dual-polarization synthetic aperture radar is parallel to the azimuth direction of the building to be measured.
[0064] The determining module is used to obtain the near-end horizontal first position and the far-end horizontal second position. For example, in the pixel-level registered image, the high-brightness bright line region along the secondary scattering side of the building in the HH-SAR image and VV-SAR image is found, and the center line of the high-brightness bright line region of HH-SAR and VV-SAR is fitted with two straight lines respectively. The average of the two straight lines is taken as the dihedral edge of the building along the ground; in the HH-SAR image, the boundary line of the shadow region along the distance to the far end is found.
[0065] The generation module is used to calculate the building height based on the flight altitude, downward viewing angle, near-end horizontal first position, and far-end horizontal second position. The distance S0 between the dihedral edge and the boundary line of the shadowed area along the distance from the corner reflector to the far end is calculated based on the distance measurement of the corner reflector, and then the estimated height h of the corresponding building is calculated, as shown in formula (2).
[0066] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.
[0067] Therefore, this application also proposes a computer-readable storage medium having a computer program stored thereon that, when executed by a processor, implements the methods described in any embodiment of this application. Additionally, a computer program product includes a computer program or instructions that, when executed by a processor, implement the methods described in any embodiment of this application.
[0068] Furthermore, this application also proposes an electronic device or computing device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the method described in any embodiment of this application.
[0069] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in one or more blocks of the flowchart illustrations and / or one or more blocks of the block diagrams.
[0070] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement the functions specified in one or more flowcharts and / or one or more block diagrams.
[0071] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more block diagrams.
[0072] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, a network interface, and memory. Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.
[0073] Figure 6 is a schematic diagram of an electronic device provided in an embodiment of this application, as another embodiment of the dual-polarization SAR image building height acquisition device of this application. The electronic device 600 shown is merely an example and should not impose any limitations on the function and scope of use of the embodiments of this application. It includes: one or more processors 620; a storage device 610 for storing one or more programs, which, when run by the one or more processors 620, enable the one or more processors 620 to implement the dual-polarization SAR image building height acquisition method provided in the embodiments of this application, the method including:
[0074] Acquire dual-polarization SAR images containing buildings using aerial remote sensing;
[0075] The location of the near-end bright line of the building image is determined based on the dual-polarization SAR image, which is taken as the first near-end horizontal position of the building along the ground.
[0076] The second horizontal position at the far end of the boundary line of the shadow area of the building image was determined based on the SAR image.
[0077] The building height is calculated based on the flight altitude, downward angle, near-end horizontal first position, and far-end horizontal second position.
[0078] The electronic device 600 also includes an input device 630 and an output device 640; the processor 620, storage device 610, input device 630 and output device 640 in the electronic device can be connected by a bus or other means, as shown in the figure, which is connected by a bus 650.
[0079] Storage device 610, as a computer-readable storage medium, can be used to store software programs, computer-executable programs, and module units, such as the program instructions corresponding to the dual-polarization SAR image building height acquisition method in this embodiment. Storage device 610 may mainly include a program storage area and a data storage area. The program storage area may store the operating system and at least one application program required for a function; the data storage area may store data created based on terminal usage. Furthermore, storage device 610 may include high-speed random access memory and non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some instances, storage device 610 may further include memory remotely located relative to processor 620, and these remote memories can be connected via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.
[0080] Input device 630 can be used to receive input digital, character, or voice information, and to generate key signal inputs related to user settings and function control of the electronic device. Output device 640 may include electronic devices such as a display screen and a speaker.
[0081] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0082] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.
Claims
1. A method for obtaining building height from dual-polarization SAR images, characterized in that, Includes the following steps: Acquire dual-polarization SAR images containing buildings using aerial remote sensing; The location of the near-end bright line of the building image is determined based on the dual-polarization SAR image, which is taken as the first near-end horizontal position of the building along the ground. The second horizontal position at the far end of the boundary line of the shadow area of the building image was determined based on the SAR image. Calculate the building height h based on the flight altitude H, the downward angle θ, the first near-end horizontal position, and the second far-end horizontal position: Where S0 is the distance between the first proximal horizontal position and the second distal horizontal position.
2. The method for obtaining building height from dual-polarization SAR images as described in claim 1, characterized in that, Determining the first horizontal position of the near-end bright line in the building image based on dual-polarization SAR imagery, specifically including: Fit the first centerline in the bright line region along the near end of the secondary scattering in the HH-SAR image; In the bright line region along the near end of the secondary scattering in the VV-SAR image, fit the second center line; The average straight line of the first centerline and the second centerline is used as the near-end edge of the building along the ground to determine the first horizontal position of the near end.
3. The method for obtaining building height from dual-polarization SAR images as described in claim 1, characterized in that, Locate the far boundary line of the shadowed area in the HH-SAR image.
4. The method for obtaining building height from dual-polarization SAR images as described in claim 1, characterized in that, Based on the SAR images of two pre-set corner reflectors on the ground, the distance between the corner reflectors is determined, and the distance S0 between the near-end horizontal first position and the far-end horizontal second position is obtained.
5. The method for obtaining building height from dual-polarization SAR images as described in claim 1, characterized in that, Two SAR radars, positioned perpendicular to the flight path and at a distance of L, are placed upwards. cr For corner reflectors, after the SAR radar generates an image, the number of pixels corresponding to the center point distance of the circular bright spots formed by the two corner reflectors in the SAR image is N. cr The number of pixels corresponding to the distance between the first horizontal position at the near end and the second horizontal position at the far end is N. p The distance between the first proximal horizontal position and the second distal horizontal position is:
6. The method for obtaining building height from dual-polarization SAR images as described in claim 1, characterized in that, The RANSAC algorithm was used to fit the centerline of the bright line region.
7. The method for obtaining building height from dual-polarization SAR images as described in claim 1, characterized in that, The radar antenna's downward viewing angle is set to θ. An aircraft equipped with a dual-polarization SAR radar takes off and enters a predetermined flight path at an altitude H. The flight path is greater than or equal to three synthetic aperture lengths and remains parallel to the azimuth of the building under test. Under standard frontal and side-view conditions, the radar generates SAR images with HH and VV polarizations.
8. A device for acquiring building height in dual-polarization SAR images, used to implement the method described in any one of claims 1 to 7, characterized in that, include: Get modules, determine modules, and generate modules; The acquisition module is used to acquire dual-polarization SAR images containing buildings through aerial remote sensing; The determining module is used to obtain the proximal horizontal first position and the distal horizontal second position; The generation module is used to calculate the building height based on the flight altitude, downward viewing angle, near-end horizontal first position, and far-end horizontal second position.
9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the method as described in any one of claims 1-7.
10. An electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1-7.