Method and device for three-dimensional reconstruction of urban buildings

Abstract

The present invention discloses a method and device for three-dimensional reconstruction of urban buildings, and relates to the field of image processing technology, wherein the method comprises: obtaining echo signals of multiple rotation angles of an array radar system; the array radar system adopts a millimeter wave frequency band; using the echo signals of multiple rotation angles to determine the main image and the secondary image; using the range Doppler RD equation, determining the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights, and the projection of the three-dimensional coordinates on the pixel points of the secondary image; the assumed height is based on the range Doppler RD projection geometry structure, and is obtained by using the incident angle, multiple rotation angles, and range resolution of the array radar system; then performing image neighborhood matching on the main image and the secondary image, and outputting the three-dimensional coordinate data of the urban building. The present invention can reduce the amount of calculation and cost of three-dimensional reconstruction of urban buildings.

Description

Technical Field

[0001] The present invention relates to the technical field of image processing, and in particular to a method and device for three-dimensional reconstruction of urban buildings. Background Art

[0002] This section is intended to provide a background or context to the embodiments of the invention recited in the claims. No admission is made that the description herein is prior art by inclusion in this section.

[0003] In the prior art, laser radar is usually used to reconstruct urban buildings in three dimensions. The principle of tomography is used during implementation, that is, multiple antennas or multiple flights are used to form elevation data, and multiple interference baselines are used to obtain the target's spatial three-dimensional information. However, this acquisition method is too complicated. Due to the limitations of the laser radar imaging principle, data cannot be efficiently collected in scenes such as rainy days and at night, making data acquisition difficult, and the complexity and cost of the radar system required for tomography will also be higher. In addition, the volume of data collected by the laser radar is large, which will cause problems such as excessive calculation and excessive memory. Summary of the invention

[0004] The embodiment of the present invention provides a method for 3D reconstruction of urban buildings, which is used to efficiently and simply obtain original data of urban buildings and reduce the amount of calculation and cost of 3D reconstruction of urban buildings. The method includes:

[0005] Acquiring echo signals of multiple rotation angles of an array radar system; the array radar system adopts a millimeter wave frequency band;

[0006] Determine the main image and the auxiliary image by using echo signals at multiple rotation angles;

[0007] Determine the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel point of the secondary image through the range Doppler RD equation; the assumed height is based on the range Doppler RD projection geometry structure, and is obtained using the array radar system incident angle, multiple rotation angles, and range resolution;

[0008] By using the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the three-dimensional coordinates projected on the pixel points of the secondary image, the main image and the secondary image are matched in the image neighborhood to output the three-dimensional coordinate data of the urban buildings.

[0009] The embodiment of the present invention further provides a three-dimensional reconstruction device for urban buildings, which is used to efficiently and simply obtain original data of urban buildings and reduce the amount of calculation and cost of three-dimensional reconstruction of urban buildings. The device includes:

[0010] An echo signal acquisition module, used to acquire echo signals of multiple rotation angles of an array radar system; the array radar system adopts a millimeter wave frequency band;

[0011] A two-dimensional imaging module, used to determine a primary image and a secondary image using echo signals at multiple rotation angles;

[0012] The image matching module is used to determine the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the pixel points of the secondary image projected with the three-dimensional coordinates through the RD equation; the assumed height is obtained based on the RD projection geometry structure and using the incident angle, multiple rotation angles and distance resolution of the array radar system; the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the pixel points of the secondary image projected with the three-dimensional coordinates are used to perform image neighborhood matching on the main image and the secondary image, and output the three-dimensional coordinate data of urban buildings.

[0013] An embodiment of the present invention further provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the above-mentioned urban building three-dimensional reconstruction method when executing the computer program.

[0014] An embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the above-mentioned method for three-dimensional reconstruction of urban buildings is implemented.

[0015] An embodiment of the present invention further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the above-mentioned urban building three-dimensional reconstruction method is implemented.

[0016] In an embodiment of the present invention, a millimeter wave frequency band is used to construct an array radar system, and multiple angles are rotated to obtain echo signals. The acquisition method is simple and efficient. The millimeter wave frequency band will not be affected even on cloudy days, foggy days or even at night, and can work normally. In addition, the millimeter wave frequency band collects near-field data, and the data volume is small. At the same time, the array radar system of the millimeter wave frequency band greatly reduces the use cost compared to the laser radar. When the echo signals of multiple rotation angles of the array radar system are used for three-dimensional reconstruction, the assumed height is used to determine the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights, and the three-dimensional coordinates are projected on the pixel points of the secondary image. The assumed height is based on the range Doppler RD projection geometry, and is obtained by using the incident angle, multiple rotation angles, and range resolution of the array radar system, thereby avoiding the tomography algorithm. The three-dimensional reconstruction algorithm in the embodiment of the present invention reduces the calculation amount of three-dimensional reconstruction of urban buildings and avoids the problem of excessive computing memory. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0018] Figure 1 Schematic diagram of the process of the method for three-dimensional reconstruction of urban buildings in an embodiment of the present invention;

[0019] Figure 2 is a geometric model of an array radar system in an embodiment of the present invention;

[0020] Figure 3 This is a specific embodiment of the method for three-dimensional reconstruction of urban buildings in an embodiment of the present invention;

[0021] Figure 4 Schematic diagram of a device for three-dimensional reconstruction of urban buildings in an embodiment of the present invention;

[0022] Figure 5 Schematic diagram of a computer device in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0024] The applicant found that the data collection method of the existing urban building 3D reconstruction technology is too complicated. Due to the limitations of the laser radar imaging principle, data cannot be collected efficiently in scenes such as rainy days and nights, making data acquisition difficult, and the complexity and cost of the radar system required for tomographic imaging will also be higher. In addition, the volume of data collected by the laser radar is large, which will cause problems such as excessive calculation and excessive memory. For this reason, the applicant proposed a method for 3D reconstruction of urban buildings.

[0025] Figure 1 FIG. 1 is a flow chart of a method for three-dimensional reconstruction of urban buildings in an embodiment of the present invention. Figure 1 As shown, the method includes:

[0026] Step 101, obtaining echo signals of a plurality of rotation angles of an array radar system; the array radar system adopts a millimeter wave frequency band;

[0027] Step 102: Determine the main image and the auxiliary image using echo signals at multiple rotation angles;

[0028] Step 103: Determine the three-dimensional coordinates corresponding to each pixel of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel of the secondary image by using the range Doppler RD equation; the assumed height is obtained based on the range Doppler RD projection geometry structure, using the incident angle, multiple rotation angles, and range resolution of the array radar system;

[0029] Step 104: using the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the three-dimensional coordinates projected on the pixel points of the secondary image, perform image neighborhood matching on the main image and the secondary image, and output the three-dimensional coordinate data of the urban buildings.

[0030] from Figure 1 It can be seen from the process shown that in the embodiment of the present invention, the array radar system is constructed by using the millimeter wave frequency band, and is rotated at multiple angles to obtain echo signals. The acquisition method is simple and efficient. The millimeter wave frequency band will not be affected even on cloudy days, foggy days or even at night, and can work normally. In addition, the millimeter wave frequency band collects near-field data, and the data volume is small. At the same time, the array radar system of the millimeter wave frequency band greatly reduces the use cost compared with the laser radar. When the echo signals of multiple rotation angles of the array radar system are used for three-dimensional reconstruction, the assumed height is used to determine the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights, and the three-dimensional coordinates are projected on the pixel points of the secondary image. The assumed height is based on the range Doppler RD projection geometry, and is obtained by using the incident angle, multiple rotation angles, and range resolution of the array radar system, thereby avoiding the tomography algorithm. The three-dimensional reconstruction algorithm in the embodiment of the present invention reduces the calculation amount of three-dimensional reconstruction of urban buildings and avoids the problem of excessive computing memory.

[0031] First, echo signals of multiple rotation angles of the array radar system are acquired, and then the main image and the sub-image are determined using the echo signals of multiple rotation angles, wherein the array radar system adopts the millimeter wave frequency band.

[0032] In one embodiment, the array radar system includes a millimeter wave radar, and the millimeter wave radar includes multiple antennas, and the multiple antennas form an array;

[0033] Acquire echo signals of array radar systems at multiple rotation angles, including:

[0034] With the center position of the array radar system as the rotation center, the array radar system is rotated to multiple angles to obtain the echo signal at each rotation angle.

[0035] Figure 2 is the geometric model of the array radar system in the embodiment of the present invention, such as Figure 2As shown, in the embodiment of the present invention, the array radar system is placed in the horizontal direction, and the center of the array radar system is used as the rotation center to rotate by angles θ1 and θ2 respectively. The antenna beam of the radar points to the target area, and the radar signal is emitted at a certain time interval, and the echo signal of the radar illumination area is received.

[0036] In other embodiments, the array radar system can be rotated to 3, 4 or other angles to transmit radar signals and receive echo signals, and those skilled in the art can implement it according to actual conditions.

[0037] In this example, the use of millimeter-wave radar to form an array radar system can fully utilize the advantages of millimeter-wave radar, eliminate machine vision blind spots, have a wide coverage range, and obtain higher-resolution images, which helps to improve the accuracy and efficiency of three-dimensional reconstruction of urban buildings.

[0038] In one embodiment, determining the primary image and the secondary image using echo signals at multiple rotation angles may include:

[0039] The back projection BP (BP for short) algorithm is adopted, with the ground as the imaging plane, and the echo signals at multiple rotation angles are imaged separately to obtain the main image and the auxiliary image.

[0040] During implementation, according to the BP algorithm, the imaging plane is taken as the ground, the horizontal direction of the ground is taken as the x-axis, and the vertical direction is taken as the y-axis. The data collected at each angle are imaged separately to obtain a main image S1 (x, y) and a sub-image S2 (x, y). Specifically, the main image is obtained by imaging the data collected at one angle, and the sub-image is obtained by imaging the data collected at another angle.

[0041] If you rotate it by multiple angles, you can get multiple secondary images.

[0042] After the main image and the sub-image are determined, in step 103, the three-dimensional coordinates corresponding to each pixel of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel of the sub-image are determined by the Range Doppler (RD) equation.

[0043] Where the altitude is assumed to be based on the range Doppler RD projection geometry, refer to Figure 2 , obtained using the incident angle, multiple rotation angles, and range resolution of the array radar system.

[0044] In one embodiment, the assumed height can be expressed as follows:

[0045] h n =(n-1)·Δh

[0046] Δh=Δρ

[0047] In the formula, h n is the assumed height, specifically any pixel point P in the main image i (x, y), i is the pixel number, x and y correspond to the horizontal and vertical coordinates of the image respectively, Δh is the assumed height interval, n is the height number, and Δρ is the distance resolution.

[0048] The RD equation is used to solve the three-dimensional coordinates of the pixels of the main image at each assumed height, and then the projection pixel position of the three-dimensional coordinates in the secondary image is solved by the RD equation. The solution of the RD equation is a common technology in the field and will not be described here.

[0049] Finally, in step 104, the main image and the secondary image are matched in the image neighborhood using the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the three-dimensional coordinates projected on the pixel points of the secondary image to output the three-dimensional coordinate data of the urban buildings.

[0050] In one embodiment, before determining the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and projecting the three-dimensional coordinates onto the pixel point in the secondary image, the method further includes:

[0051] Using a first threshold, the pixels of the main image are screened to obtain a plurality of strong scattering pixels; the first threshold is used to limit the intensity value of the pixel;

[0052] Determine the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel point of the secondary image by using the range Doppler RD equation, including:

[0053] Determine the three-dimensional coordinates corresponding to each strong scattering pixel point of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel point of the secondary image by using the range Doppler RD equation;

[0054] Using the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the three-dimensional coordinates projected on the pixel points of the secondary image, the main image and the secondary image are subjected to image neighborhood matching calculation, and the three-dimensional coordinate data of the urban building is output, including:

[0055] By using the three-dimensional coordinates corresponding to each strong scattering pixel point of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel points of the secondary image, the main image and the secondary image are subjected to image neighborhood matching calculation to output the three-dimensional coordinate data of the urban buildings.

[0056] In this example, strong scattering pixels of the main image with amplitude greater than the first threshold can be selected. The first threshold is preferably -40dB, and can also be selected empirically based on the distribution of strong points in the image. Then, the three-dimensional coordinate estimation and image matching are calculated based on the strong scattering pixels of the main image, which can improve the efficiency of image neighborhood matching and thus improve the efficiency of three-dimensional reconstruction of urban buildings.

[0057] In one embodiment, using the three-dimensional coordinates corresponding to each strong scattering pixel point of the main image at multiple assumed heights and the three-dimensional coordinates projected on the pixel points of the secondary image, performing image neighborhood matching calculation on the main image and the secondary image, and outputting the three-dimensional coordinate data of the urban building may include:

[0058] Set the matching window;

[0059] Move the matching window to calculate the amplitude difference between the strong scattering pixels in the main image and the pixels in the secondary image;

[0060] Screening out strongly scattered pixel points in the main image and pixel points in the auxiliary image whose amplitude differences are less than a second threshold;

[0061] Based on the strong scattering pixel points in the main image and the pixel points in the auxiliary image whose amplitude difference is less than the second threshold, the matching window is moved, and the main image is calculated in sequence at the strong scattering pixel point P according to the following formula i The matching window data of (x, y) and the secondary image in P i (x′ n , y′ n ) The correlation coefficient r(x, y) of the matching window data of the pixel point is obtained to obtain multiple correlation coefficient values:

[0062]

[0063] Where E[*] represents the mathematical expectation, S1 is the main image at the strong scattering pixel point P i (x, y) matching window data, S2 is the secondary image at P i (x′ n , y′ n ) The matching window data of the pixel, i represents the i-th pixel;

[0064] Among multiple correlation coefficient values, the three-dimensional coordinate corresponding to the maximum correlation coefficient is selected as the strong scattering pixel point P i (x, y) three-dimensional coordinates.

[0065] In specific implementation, a 3×3 or 5×5 matching window can be selected. First, the amplitude difference between the two images is calculated. When the difference is less than the second threshold, the second threshold is generally preferably within 3dB, and can also be calculated according to the following formula:

[0066]

[0067] Where σ is the second threshold, S1 is the main image at the strong scattering pixel point P i (x, y) matching window data, S2 is the secondary image at P i (x′ n , y′ n ) pixel matching window data.

[0068] Then calculate the main image in P i The matching window data at position (x, y) and the secondary image at position P i (x′ n , y′ n )’s matching window data.

[0069] Finally, the three-dimensional coordinate corresponding to the maximum value of the correlation coefficient is selected as the strong scattering pixel point P i (x, y) three-dimensional coordinates.

[0070] When there are multiple sub-images, the sub-image with the most sub-image pixels whose amplitude difference is less than the second threshold can be obtained by screening through the second threshold as the best sub-image, and the correlation coefficient can be screened and calculated.

[0071] Figure 3 This is a specific embodiment of the method for three-dimensional reconstruction of urban buildings in an embodiment of the present invention. Figure 3 As shown, the overall solution process of the embodiment of the present invention is shown, including:

[0072] Step 1: acquiring data, i.e. acquiring echo signals of the array radar system at multiple rotation angles;

[0073] Step 2: two-dimensional imaging, i.e. obtaining a main image and a sub-image using the echo signal;

[0074] Step 3: Use the main image and the secondary image to perform SAR image matching;

[0075] Step 4: Based on the matching results, output the optimal height estimate and determine the three-dimensional coordinate data of the urban building.

[0076] In summary, the present invention has the following beneficial effects:

[0077] 1. High-resolution imaging: The rotating three-dimensional imaging of the millimeter-wave array radar system can provide higher-resolution target images because it can observe the target at multiple angles, thereby better distinguishing the details and shape of the target.

[0078] 2. Eliminate the problems of large amount of calculation, difficult data acquisition and high memory usage when using tomographic SAR to perform three-dimensional imaging of complex structure buildings, making the three-dimensional imaging more efficient.

[0079] The rotation of the 3 mm wave band array radar system can eliminate blind spots to a certain extent, ensure a wider coverage area, and reduce missed detections and false detections.

[0080] The present invention also provides a 3D reconstruction device for urban buildings, as described in the following embodiments. Since the principle of solving the problem by the device is similar to that of the 3D reconstruction method for urban buildings, the implementation of the device can refer to the implementation of the 3D reconstruction method for urban buildings, and the repeated parts will not be repeated.

[0081] Figure 4 FIG. 1 is a schematic diagram of a device for 3D reconstruction of urban buildings in an embodiment of the present invention. Figure 4 As shown, the device comprises:

[0082] The echo signal acquisition module 401 is used to acquire echo signals of multiple rotation angles of the array radar system; the array radar system adopts the millimeter wave frequency band;

[0083] A two-dimensional imaging module 402, used to determine a primary image and a secondary image using echo signals at multiple rotation angles;

[0084] The image matching module 403 is used to determine the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the pixel points of the sub-image projected with the three-dimensional coordinates through the range Doppler RD equation; the assumed height is obtained based on the range Doppler RD projection geometry structure, using the incident angle, multiple rotation angles, and range resolution of the array radar system; using the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the three-dimensional coordinates projected on the pixel points of the sub-image, the main image and the sub-image are matched in the image neighborhood, and the three-dimensional coordinate data of the urban building is output.

[0085] In one embodiment, the array radar system includes a millimeter wave radar, and the millimeter wave radar includes multiple antennas, and the multiple antennas form an array;

[0086] The echo signal acquisition module 401 is specifically used for:

[0087] With the center position of the array radar system as the rotation center, the array radar system is rotated to multiple angles to obtain the echo signal at each rotation angle.

[0088] In one embodiment, the two-dimensional imaging module 402 is specifically used for:

[0089] The back-projection BP algorithm is used, with the ground as the imaging plane, to image the echo signals at multiple rotation angles separately to obtain the main image and the auxiliary image.

[0090] In one embodiment, the assumed height is expressed by the following formula:

[0091] h n =(n-1)·Δh

[0092] Δh=Δρ

[0093] In the formula, h n is the assumed height, Δh is the assumed height interval, n is the height number, and Δρ is the distance resolution.

[0094] In one embodiment, the apparatus further comprises:

[0095] A strong pixel screening module is used to screen the pixels of the main image using a first threshold value before the image matching module 403 determines the three-dimensional coordinates corresponding to each pixel of the main image at multiple assumed heights and projects the three-dimensional coordinates into the pixel in the secondary image, so as to obtain multiple strong scattered pixel points; the first threshold value is used to limit the intensity value of the pixel point;

[0096] The image matching module 403 is specifically used for:

[0097] Determine the three-dimensional coordinates corresponding to each strong scattering pixel point of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel point of the secondary image by using the range Doppler RD equation;

[0098] By using the three-dimensional coordinates corresponding to each strong scattering pixel point of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel points of the secondary image, the main image and the secondary image are subjected to image neighborhood matching calculation to output the three-dimensional coordinate data of the urban buildings.

[0099] In one embodiment, the image matching module 403 is specifically used for:

[0100] Set the matching window;

[0101] Move the matching window to calculate the amplitude difference between the strong scattering pixels in the main image and the pixels in the secondary image;

[0102] Screening out strongly scattered pixel points in the main image and pixel points in the auxiliary image whose amplitude differences are less than a second threshold;

[0103] Based on the strong scattering pixel points in the main image and the pixel points in the auxiliary image whose amplitude difference is less than the second threshold, the matching window is moved, and the main image is calculated in sequence at the strong scattering pixel point P according to the following formula i The matching window data of (x, y) and the secondary image in P i (x′ n , y′ n ) The correlation coefficient r(x, y) of the matching window data of the pixel point is obtained to obtain multiple correlation coefficient values:

[0104]

[0105] Where E[*] represents the mathematical expectation, S1 is the main image at the strong scattering pixel point P i (x, y) matching window data, S2 is the secondary image at P i (x′ n , y′ n ) The matching window data of the pixel, i represents the i-th pixel;

[0106] Among multiple correlation coefficient values, the three-dimensional coordinate corresponding to the maximum correlation coefficient is selected as the strong scattering pixel point P i (x, y) three-dimensional coordinates.

[0107] Figure 5 Schematic diagram of a computer device in an embodiment of the present invention. Figure 5 As shown, an embodiment of the present invention further provides a computer device 500, including a processor 501, a memory 502, and a computer program 503 stored in the memory 502 and executable on the processor 501, wherein the processor 501 implements the above-mentioned urban building three-dimensional reconstruction method when executing the computer program 503.

[0108] An embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the above-mentioned method for three-dimensional reconstruction of urban buildings is implemented.

[0109] An embodiment of the present invention further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the above-mentioned urban building three-dimensional reconstruction method is implemented.

[0110] In an embodiment of the present invention, a millimeter wave frequency band is used to construct an array radar system, and multiple angles are rotated to obtain echo signals. The acquisition method is simple and efficient. The millimeter wave frequency band will not be affected even on cloudy days, foggy days or even at night, and can work normally. In addition, the millimeter wave frequency band collects near-field data, and the data volume is small. At the same time, the array radar system of the millimeter wave frequency band greatly reduces the use cost compared to the laser radar. When the echo signals of multiple rotation angles of the array radar system are used for three-dimensional reconstruction, the assumed height is used to determine the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights, and the three-dimensional coordinates are projected on the pixel points of the secondary image. The assumed height is based on the range Doppler RD projection geometry, and is obtained by using the incident angle, multiple rotation angles, and range resolution of the array radar system, thereby avoiding the tomography algorithm. The three-dimensional reconstruction algorithm in the embodiment of the present invention reduces the calculation amount of three-dimensional reconstruction of urban buildings and avoids the problem of excessive computing memory.

[0111] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented 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.

[0112] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0113] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0114] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0115] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for three-dimensional reconstruction of urban buildings, characterized in that: include: Acquiring echo signals of multiple rotation angles of an array radar system; the array radar system adopts a millimeter wave frequency band; Determine the main image and the auxiliary image by using echo signals at multiple rotation angles; Determine the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel point of the secondary image through the range Doppler RD equation; the assumed height is based on the range Doppler RD projection geometry structure, and is obtained using the array radar system incident angle, multiple rotation angles, and range resolution; Using the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the three-dimensional coordinates projected on the pixel points of the secondary image, the main image and the secondary image are matched in the image neighborhood to output the three-dimensional coordinate data of the urban buildings; The assumed height is expressed by the following formula: h n =(n-1)·Δh Δh=Δρ In the formula, h n is the assumed height of any pixel of the main image, Δh is the assumed height interval, n is the height sequence number, and Δρ is the distance resolution.

2. The method according to claim 1, characterized in that The array radar system includes a millimeter wave radar, and the millimeter wave radar includes multiple antennas, and the multiple antennas form an array; Acquire echo signals of array radar systems at multiple rotation angles, including: With the center position of the array radar system as the rotation center, the array radar system is rotated to multiple angles to obtain the echo signal at each rotation angle.

3. The method according to claim 1, characterized in that The main image and the auxiliary image are determined by using echo signals at multiple rotation angles, including: The back-projection BP algorithm is used, with the ground as the imaging plane, to image the echo signals at multiple rotation angles separately to obtain the main image and the auxiliary image.

4. The method according to claim 1, characterized in that Before determining the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and projecting the three-dimensional coordinates onto the pixel point in the secondary image, the method further includes: Using a first threshold, the pixels of the main image are screened to obtain a plurality of strong scattering pixels; the first threshold is used to limit the intensity value of the pixel; Determine the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel point of the secondary image by using the range Doppler RD equation, including: Determine the three-dimensional coordinates corresponding to each strong scattering pixel point of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel point of the secondary image by using the range Doppler RD equation; Using the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the three-dimensional coordinates projected on the pixel points of the secondary image, the main image and the secondary image are subjected to image neighborhood matching calculation, and the three-dimensional coordinate data of the urban building is output, including: By using the three-dimensional coordinates corresponding to each strong scattering pixel point of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel points of the secondary image, the main image and the secondary image are subjected to image neighborhood matching calculation to output the three-dimensional coordinate data of the urban buildings.

5. The method according to claim 4, characterized in that Using the three-dimensional coordinates corresponding to each strong scattering pixel point of the main image at multiple assumed heights and the three-dimensional coordinates projected on the pixel points of the secondary image, the main image and the secondary image are subjected to image neighborhood matching calculation, and the three-dimensional coordinate data of the urban building is output, including: Set the matching window; Move the matching window to calculate the amplitude difference between the strong scattering pixels in the main image and the pixels in the secondary image; Screening out strongly scattered pixel points in the main image and pixel points in the auxiliary image whose amplitude differences are less than a second threshold; Based on the strong scattering pixel points in the main image and the pixel points in the auxiliary image whose amplitude difference is less than the second threshold, the matching window is moved, and the main image is calculated in sequence at the strong scattering pixel point P according to the following formula i The matching window data of (x, y) and the secondary image are in P i (x′ n , y′ n )The correlation coefficient r(x,y) of the matching window data of the pixel point is obtained, and multiple correlation coefficient values ​​are obtained: Where E[*] represents the mathematical expectation, S1 is the main image at the strong scattering pixel point P i (x, y) matching window data, S2 is the secondary image at P i (x′ n , y′ n ) The matching window data of the pixel, i represents the i-th pixel; Among multiple correlation coefficient values, the three-dimensional coordinate corresponding to the maximum correlation coefficient is selected as the strong scattering pixel point P i The three-dimensional coordinates of (x,y).

6. A three-dimensional reconstruction device for urban buildings, characterized in that: include: An echo signal acquisition module, used to acquire echo signals of multiple rotation angles of an array radar system; the array radar system adopts a millimeter wave frequency band; A two-dimensional imaging module, used to determine a primary image and a secondary image using echo signals at multiple rotation angles; An image matching module is used to determine the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the projection of the three-dimensional coordinates on the pixel point of the secondary image through the RD equation; the assumed height is based on the RD projection geometry structure, and is obtained by using the incident angle, multiple rotation angles, and range resolution of the array radar system; Using the three-dimensional coordinates corresponding to each pixel point of the main image at multiple assumed heights and the three-dimensional coordinates projected on the pixel points of the secondary image, the main image and the secondary image are matched in the image neighborhood to output the three-dimensional coordinate data of the urban buildings; The assumed height is expressed by the following formula: h n =(n-1)·Δh Δh=Δρ In the formula, h n is the assumed height of any pixel of the main image, Δh is the assumed height interval, n is the height sequence number, and Δρ is the distance resolution.

7. A computer 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, the method according to any one of claims 1 to 5 is implemented.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

9. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

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