A method and device for quickly generating digital orthophoto maps based on point clouds

Abstract

The present invention relates to a method and device for quickly generating a digital orthophoto map based on point cloud. The method divides point cloud data into blocks according to a preset size to obtain a plurality of digital elevation model data blocks. The camera imaging model is used to calculate the world coordinates of each pixel point in the frame image, and the weight of the world coordinate point corresponding to each pixel point on the frame image is calculated. If the world coordinate point P corresponding to the pixel point M is in the frame image I, the weight of the world coordinate point P corresponding to the pixel point M is calculated. i The weight #imgabs0# on the image is greater than P in the frame I i‑1 The weight #imgabs1# assigns the pixel value of pixel point M in the frame image to the world coordinate point P, otherwise skipping. This step is repeated until all pixels in all frames are traversed, obtaining the pixel value corresponding to any point in the point cloud data, and generating a digital orthophoto. This processing method uses less memory and improves CPU utilization. It eliminates the need for phased array and aerial triangulation, and can process areas with weak or no texture, making it more applicable than conventional software.

Description

Technical Field

[0001] The present invention relates to the technical field of image processing, and in particular to a method and device for quickly generating a digital orthophoto map based on point cloud. Background Art

[0002] Aerial photogrammetry is the primary means of acquiring basic geographic information data, and its primary task is to produce digital orthophoto maps (DOMs). Traditional aerial photogrammetry requires the deployment of ground control points, resulting in complex mapping processes and long production cycles. This process fails to meet the current requirements of DOMs, which means that geographic information data cannot be updated in a timely manner. To address these issues, POS (Position and Orientation System) positioning and attitude determination technology provides an effective solution. Its core concept is to install a POS system on an unmanned aerial vehicle (UAV) to achieve direct ground target positioning, eliminating the requirement for the deployment of ground control points. However, DOMs produced without ground control points suffer from low accuracy.

[0003] Existing point cloud-based DOM generation solutions primarily use aerial triangulation calculations from drone-captured image frames to generate a corrected point cloud with a certain degree of accuracy. The drone imagery is then back-calculated to the pixels of the resulting DOM using these corrected coordinates. Aerial triangulation can eliminate pixel errors in overlapping areas of drone imagery, but the calculation is slow. Using traditional image processing software for drone imagery processing often takes several hours to output orthophotos.

[0004] During field operations, it is often necessary to quickly preview the regional data after the drone flight, and conventional calculation methods cannot meet this requirement. Therefore, a method for rapid DOM generation based on the hardware conditions of a "lidar system equipped with an orthophoto camera" is proposed to achieve functions such as rapid preview of digital orthophoto maps (DOM) in actual operations. Summary of the Invention

[0005] In view of the technical problems existing in the prior art, the present invention provides a method and device for quickly generating digital orthophoto maps based on point clouds, so as to realize functions such as quick preview of digital orthophoto maps (DOM) in actual operations.

[0006] The technical solution of the present invention to solve the above technical problems is as follows:

[0007] In a first aspect, the present invention provides a method for rapidly generating a digital orthophoto map based on a point cloud, comprising:

[0008] S1, obtains the point cloud data collected by the radar system and the frame image taken by the orthophoto camera;

[0009] S2, dividing the point cloud data into blocks according to a preset size to obtain multiple digital elevation model data blocks;

[0010] S3, extracting the digital elevation model data blocks intersecting with the current frame image according to the point cloud coordinates and the world coordinates of the four corner vertices of the current frame image;

[0011] S4, using the camera imaging model to calculate the world coordinates of each pixel in the current frame image, and calculate the weight of the world coordinate point corresponding to each pixel in the current frame image;

[0012] S5, traverse all the pixels in the current frame image, if the world coordinate point P corresponding to the pixel point M is in the current frame image I i The weight on Greater than the world coordinate point P in the previous frame image I i-1 Weight Then assign the pixel value of pixel point M in the current frame image to the world coordinate point P, otherwise skip the assignment operation of the world coordinate point P;

[0013] S6, select the next frame image as the current frame and jump to step S3 until all frame images are traversed, obtain the pixel value corresponding to any point cloud in the point cloud data, and generate a digital orthophoto map.

[0014] Furthermore, the digital elevation model data blocks intersecting with the current frame image are extracted according to the point cloud coordinates and the world coordinates of the four corner vertices of the current frame image, including:

[0015] Calculate the world coordinates of the four corner vertices of the current frame image and construct the plane bounding box corresponding to the current frame image;

[0016] Constructing a point cloud bounding box for each digital elevation model data block according to the XY coordinates of the point cloud contained in the digital elevation model data block;

[0017] Perform an intersection operation on the plane bounding box and any one of the point cloud bounding boxes. If the result is not empty, bind the current frame image to the digital elevation model data block that intersects with it.

[0018] Furthermore, the weight of the world coordinate point corresponding to the pixel point on the current frame image is calculated as: the cosine of the angle between the line connecting the pixel point and the camera projection center and the line connecting the camera projection center and the image bottom point.

[0019] Furthermore, step S5 further includes: if the world coordinate point P corresponding to the pixel point M is in the current frame image I i The weight on Greater than the world coordinate point P in the previous frame image I i-1 Weight It is determined whether the pixel point M of the current frame image is blocked when it is captured. If not, the pixel value of the pixel point M in the current frame image is assigned to the world coordinate point P. If occlusion exists, the assignment operation to the world coordinate point P is skipped.

[0020] Furthermore, the occlusion judgment method includes:

[0021] For the world coordinate point P corresponding to the pixel point M, the line connecting the world coordinate point P and the camera projection center is recorded as L0, and the line connecting the world coordinate point P and the image base point is recorded as L1;

[0022] Through the projection relationship, the actual distance of a single pixel on the frame image corresponding to the world coordinate system is obtained. This distance is used as the backtracking step length. Starting from the world coordinate point P, points on L1 are extracted along the L1 direction according to the backtracking step length.

[0023] For any point (x, y) on the extracted L1, obtain the elevation value Z1 corresponding to (x, y) based on the point cloud data, and calculate the elevation value Z0 corresponding to (x, y) based on the straight line L0;

[0024] If Z1 is greater than Z0, it means that the world coordinate point P corresponding to the pixel point M is blocked.

[0025] In a second aspect, the present invention provides a device for rapidly generating a digital orthophoto map based on a point cloud, comprising:

[0026] Data acquisition module, which obtains point cloud data collected by the radar system and frame images taken by the orthophoto camera;

[0027] The DEM block module divides the point cloud data into blocks according to the preset size to obtain multiple digital elevation model data blocks;

[0028] The intersection module extracts the digital elevation model data blocks that intersect with the current frame image based on the point cloud coordinates and the world coordinates of the four corner vertices of the current frame image;

[0029] The weight calculation module uses the camera imaging model to calculate the world coordinates of each pixel in the current frame image, and calculates the weight of the world coordinate point corresponding to each pixel in the current frame image;

[0030] The weight judgment and assignment module traverses all the pixels in the current frame image. If the world coordinate point P corresponding to the pixel point M is in the current frame image I i The weight on Greater than the world coordinate point P in the previous frame image I i-1 Weight Then assign the pixel value of pixel point M in the current frame image to the world coordinate point P, otherwise skip the assignment operation of the world coordinate point P;

[0031] The digital orthophoto generation module is used to generate a digital orthophoto map after traversing all frame images and obtaining the pixel value corresponding to any point cloud in the point cloud data.

[0032] Furthermore, the intersection module includes:

[0033] The first construction module calculates the world coordinates of the four corner vertices of the current frame image and constructs the plane bounding box corresponding to the current frame image;

[0034] The second construction module constructs a point cloud bounding box of each digital elevation model data block according to the XY coordinates of the point cloud contained in the digital elevation model data block;

[0035] The intersection operation and binding module performs an intersection operation on the plane bounding box and any one of the point cloud bounding boxes. If the result is not empty, the current frame image is bounded with the digital elevation model data block that intersects with it.

[0036] Furthermore, the weight judgment and assignment module further includes an occlusion judgment module;

[0037] The occlusion judgment module is used to judge the world coordinate point P corresponding to the pixel point M in the current frame image I i The weight on Greater than the world coordinate point P in the previous frame image I i-1 Weight Then, determine whether the pixel point M of the current frame image is blocked when shooting. If not, assign the pixel value of the pixel point M in the current frame image to the world coordinate point P. If occlusion exists, skip the assignment operation of the world coordinate point P.

[0038] In a third aspect, the present invention provides an electronic device, comprising:

[0039] Memory for storing computer software programs;

[0040] The processor is used to read and execute the computer software program, thereby realizing the method for quickly generating a digital orthophoto map based on a point cloud as described in the first aspect of the present invention.

[0041] In a fourth aspect, the present invention provides a non-transitory computer-readable storage medium, wherein the storage medium stores a computer software program for implementing a method for rapidly generating a digital orthophoto map based on a point cloud as described in the first aspect of the present invention.

[0042] The beneficial effects of the present invention are:

[0043] This solution can reduce DOM generation time by four times compared to conventional image processing software, while also reducing memory usage and increasing CPU utilization. It eliminates the need for phased image processing and aerial triangulation, and can process weakly textured or non-textured areas, making it more applicable than conventional software. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of the hardware system structure provided by an embodiment of the present invention;

[0045] Figure 2 A schematic flow chart of a method for rapidly generating a digital orthophoto map based on a point cloud according to an embodiment of the present invention;

[0046] Figure 3 A schematic structural diagram of a device for rapidly generating digital orthophoto images based on point clouds provided by an embodiment of the present invention;

[0047] Figure 4 A schematic diagram of an electronic device according to an embodiment of the present invention;

[0048] Figure 5 A schematic diagram of an embodiment of a computer-readable storage medium provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0050] The present invention is based on the hardware system of a lidar system equipped with an orthophoto camera. It can directly obtain the camera's internal and external azimuth element data required for DOM generation. When the accuracy is sufficient, aerial triangulation calculations can be eliminated, thereby greatly improving the efficiency of DOM generation.

[0051] Since there is no aerial triangulation, problems caused by aerial triangulation failure are avoided.

[0052] In areas with weak texture or no texture, image processing cannot find feature points and is therefore ineffective. However, this solution does not have this problem because it uses pixel projection for direct calculation.

[0053] In terms of hardware, the system uses an ARM core board as the central processing unit, and includes GNSS board, IMU, lidar, orthophoto camera, data and photo storage units, etc. The system structure is as follows Figure 1 shown.

[0054] The system collects GNSS observation data (supporting all four constellations, including GPS, GLONASS, BeiDou, and Galileo) through the GNSS board. The GNSS board's PPS synchronization pulse signals and GPRMC timing data provide a unified time tag for the entire system, synchronizing time information across all units. The core board stores MEMS and ephemeris data from the GNSS board onto a data storage card for later processing.

[0055] The inertial navigation module (IMU) sends real-time attitude information to the core board at a set frequency. The core board adds a unified time tag (GNSS timing) to each frame of data. The core board then stores the IMU data including the time tag on the data storage card for later use in data processing.

[0056] The lidar directly reads the PPS synchronization pulse signal and GPRMC timing data of the GNSS board. The lidar adds a time tag to the point cloud data and sends the data to the core board via Ethernet. The core board then stores the lidar data on the data storage card for use in later data processing.

[0057] The orthophoto camera takes a photo after receiving a trigger signal from the core board. Simultaneously, it sends a pulse signal back to the core board, which records the precise time of the feedback signal and stores it on a data storage card. The photo is then stored on a dedicated photo storage card. Later, during data processing, a matching algorithm can be used to establish a one-to-one match between the photo capture time and the photo itself.

[0058] Through a unified time tag mechanism, the time tag accuracy of laser point cloud and IMU data is better than 1μs, and the time tag accuracy of image data is better than 1ms.

[0059] Based on the above hardware system, the embodiment of the present invention provides a method for quickly generating digital orthophoto maps based on point clouds, such as Figure 2 As shown, including:

[0060] S1, obtains the point cloud data collected by the radar system and the frame images taken by the orthophoto camera and performs preprocessing.

[0061] S2, the point cloud data is divided into blocks according to the preset size, resulting in multiple digital elevation model data blocks. When the data volume is too large, the memory cannot accommodate it. Therefore, the data is divided into blocks to reduce memory usage and enable parallel processing.

[0062] S3, extracting the digital elevation model data blocks intersecting with the current frame image according to the point cloud coordinates and the world coordinates of the four corner vertices of the current frame image.

[0063] First, calculate the world coordinates of the four corner vertices of the current frame image and construct the plane bounding box corresponding to the current frame image;

[0064] Secondly, construct the point cloud bounding box of each digital elevation model data block according to the XY coordinates of the point cloud contained in the digital elevation model data block;

[0065] Then, an intersection operation is performed on the plane bounding box and any one of the point cloud bounding boxes. If the result is not empty, the current frame image is bound to the digital elevation model data block that intersects with it.

[0066] S4, using the camera imaging model to calculate the world coordinates of each pixel in the current frame image, and calculate the weight of the world coordinate point corresponding to each pixel in the current frame image.

[0067] When processing drone images, we traverse the pixels of the current image and use a calculation equation to obtain the world coordinates of each pixel. At this point, the world coordinates only have X and Y values. Using the DEM, we can then obtain the Z value of the point, and thus the world coordinates. Since the point corresponds to a pixel in the drone image, we can also obtain the color value of the world coordinate point. The calculation equation (camera imaging model) is as follows:

[0068] sp=A[R|t]P ω

[0069] Where p is the pixel coordinate, P ω is the world coordinate system, A is the camera intrinsic matrix, R and t are used to describe the rotation and translation matrices between the world coordinate system and the camera coordinate system, and s is the scaling factor of the projection transformation.

[0070] The weight of the world coordinate point corresponding to the pixel point on the current frame image is calculated as: the cosine of the angle between the line connecting the pixel point and the camera projection center and the line connecting the camera projection center and the image bottom point.

[0071] S5, traverse all the pixels in the current frame image, if the world coordinate point P corresponding to the pixel point M is in the current frame image I i The weight on Greater than the world coordinate point P in the previous frame image I i-1 Weight The pixel value of the pixel point M in the current frame image is assigned to the world coordinate point P, otherwise the assignment operation to the world coordinate point P is skipped.

[0072] Since drone images have overlapping areas, the same world coordinate point has different weights in different images. Therefore, the size of the weight can be used to preliminarily determine whether there is image overlap.

[0073] S6, select the next frame image as the current frame and jump to step S3 until all frame images are traversed, obtain the pixel value corresponding to any point cloud in the point cloud data, and generate a digital orthophoto map.

[0074] On the basis of the above embodiment, step S5 further includes: if the world coordinate point P corresponding to the pixel point M is in the current frame image I i The weight on Greater than the world coordinate point P in the previous frame image I i-1 Weight The algorithm then determines whether pixel point M in the current frame image was obstructed during capture. If not, the pixel value of pixel point M in the current frame image is assigned to world coordinate point P. If occlusion is present, the assignment to world coordinate point P is skipped. Occlusion determination is used to further address the issue of overlapping pixel projections. Calculating world coordinates from pixel coordinates can result in calculation errors for images taken at different angles. This error can cause pixels at higher elevations to be calculated for pixels at lower elevations.

[0075] Preferably, the occlusion determination method includes:

[0076] For the world coordinate point P corresponding to the pixel point M, the line connecting the world coordinate point P and the camera projection center is recorded as L0, and the line connecting the world coordinate point P and the image base point is recorded as L1;

[0077] Through the projection relationship, the actual distance of a single pixel on the frame image corresponding to the world coordinate system is obtained. This distance is used as the backtracking step length. Starting from the world coordinate point P, points on L1 are extracted along the L1 direction according to the backtracking step length.

[0078] For any point (x, y) on the extracted L1, obtain the elevation value Z1 corresponding to (x, y) based on the point cloud data, and calculate the elevation value Z0 corresponding to (x, y) based on the straight line L0;

[0079] If Z1 is greater than Z0, it means that the world coordinate point P corresponding to the pixel point M is blocked.

[0080] In addition to the occlusion judgment method used in this embodiment, the occlusion judgment method can be determined by determining whether the pixel values ​​of the same world coordinate point in different frame images are the same. The specific judgment method will not be described in detail here.

[0081] This solution can reduce DOM generation time by four times compared to conventional image processing software, while also reducing memory usage and increasing CPU utilization. It eliminates the need for phased image processing and aerial triangulation, and can process weakly textured or non-textured areas, making it more applicable than conventional software.

[0082] like Figure 3As shown, an embodiment of the present invention further provides a device for quickly generating a digital orthophoto map based on a point cloud, comprising:

[0083] Data acquisition module, which obtains point cloud data collected by the radar system and frame images taken by the orthophoto camera;

[0084] The DEM block module divides the point cloud data into blocks according to the preset size to obtain multiple digital elevation model data blocks;

[0085] The intersection module extracts the digital elevation model data blocks that intersect with the current frame image based on the point cloud coordinates and the world coordinates of the four corner vertices of the current frame image;

[0086] The weight calculation module uses the camera imaging model to calculate the world coordinates of each pixel in the current frame image, and calculates the weight of the world coordinate point corresponding to each pixel in the current frame image;

[0087] The weight judgment and assignment module traverses all the pixels in the current frame image. If the world coordinate point P corresponding to the pixel point M is in the current frame image I i The weight on Greater than the world coordinate point P in the previous frame image I i-1 Weight Then assign the pixel value of pixel point M in the current frame image to the world coordinate point P, otherwise skip the assignment operation of the world coordinate point P;

[0088] The digital orthophoto generation module is used to generate a digital orthophoto map after traversing all frame images and obtaining the pixel value corresponding to any point cloud in the point cloud data.

[0089] Furthermore, the intersection module includes:

[0090] The first construction module calculates the world coordinates of the four corner vertices of the current frame image and constructs the plane bounding box corresponding to the current frame image;

[0091] The second construction module constructs a point cloud bounding box of each digital elevation model data block according to the XY coordinates of the point cloud contained in the digital elevation model data block;

[0092] The intersection operation and binding module performs an intersection operation on the plane bounding box and any one of the point cloud bounding boxes. If the result is not empty, the current frame image is bounded with the digital elevation model data block that intersects with it.

[0093] Furthermore, the weight judgment and assignment module further includes an occlusion judgment module;

[0094] The occlusion judgment module is used to judge the world coordinate point P corresponding to the pixel point M in the current frame image I iThe weight on Greater than the world coordinate point P in the previous frame image I i-1 Weight Then, determine whether the pixel point M of the current frame image is blocked when shooting. If not, assign the pixel value of the pixel point M in the current frame image to the world coordinate point P. If occlusion exists, skip the assignment operation of the world coordinate point P.

[0095] See also Figure 4 , Figure 4 Schematic diagram of an embodiment of an electronic device provided by an embodiment of the present invention. Figure 4 As shown, an embodiment of the present invention provides an electronic device 500, including a memory 510, a processor 520, and a computer program 511 stored in the memory 520 and executable on the processor 520. When the processor 520 executes the computer program 511, the following steps are implemented:

[0096] S1, obtains the point cloud data collected by the radar system and the frame image taken by the orthophoto camera and performs preprocessing;

[0097] S2, dividing the point cloud data into blocks according to a preset size to obtain multiple digital elevation model data blocks;

[0098] S3, extracting the digital elevation model data blocks intersecting with the current frame image according to the point cloud coordinates and the world coordinates of the four corner vertices of the current frame image;

[0099] S4, using the camera imaging model to calculate the world coordinates of each pixel in the current frame image, and calculate the weight of the world coordinate point corresponding to each pixel in the current frame image;

[0100] S5, traverse all the pixels in the current frame image, if the world coordinate point P corresponding to the pixel point M is in the current frame image I i The weight on Greater than the world coordinate point P in the previous frame image I i-1 Weight Then assign the pixel value of pixel point M in the current frame image to the world coordinate point P, otherwise skip the assignment operation of the world coordinate point P;

[0101] S6, select the next frame image as the current frame and jump to step S3 until all frame images are traversed, obtain the pixel value corresponding to any point cloud in the point cloud data, and generate a digital orthophoto map.

[0102] See also Figure 5 , Figure 5 Schematic diagram of an embodiment of a computer-readable storage medium provided in an embodiment of the present invention. Figure 5As shown, this embodiment provides a computer-readable storage medium 600 on which a computer program 611 is stored. When the computer program 611 is executed by a processor, the following steps are implemented:

[0103] S1, obtains the point cloud data collected by the radar system and the frame images taken by the orthophoto camera and performs preprocessing;

[0104] S2, dividing the point cloud data into blocks according to a preset size to obtain multiple digital elevation model data blocks;

[0105] S3, extracting the digital elevation model data blocks intersecting with the current frame image according to the point cloud coordinates and the world coordinates of the four corner vertices of the current frame image;

[0106] S4, using the camera imaging model to calculate the world coordinates of each pixel in the current frame image, and calculate the weight of the world coordinate point corresponding to each pixel in the current frame image;

[0107] S5, traverse all the pixels in the current frame image, if the world coordinate point P corresponding to the pixel point M is in the current frame image I i The weight on Greater than the world coordinate point P in the previous frame image I i-1 Weight Then assign the pixel value of pixel point M in the current frame image to the world coordinate point P, otherwise skip the assignment operation of the world coordinate point P;

[0108] S6, select the next frame image as the current frame and jump to step S3 until all frame images are traversed, obtain the pixel value corresponding to any point cloud in the point cloud data, and generate a digital orthophoto map.

[0109] It should be noted that, in the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0110] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, 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 magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0111] 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 flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts 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, a special-purpose computer, an embedded computer, 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 flowcharts and / or block diagrams. 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.

[0112] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0113] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0114] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0115] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications of the present invention fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for rapidly generating digital orthophotos based on point clouds, characterized in that: include: S1, obtains the point cloud data collected by the radar system and the frame image taken by the orthophoto camera; S2, dividing the point cloud data into blocks according to a preset size to obtain multiple digital elevation model data blocks; S3, extracting the digital elevation model data blocks intersecting with the current frame image according to the point cloud coordinates and the world coordinates of the four corner vertices of the current frame image; S4, using the camera imaging model to calculate the world coordinates of each pixel in the current frame image, and calculate the weight of the world coordinate point corresponding to each pixel in the current frame image; S5, traverse all the pixels in the current frame image, if the pixel M Corresponding world coordinate point P In the current frame image I i The weight on Greater than the world coordinate point P In the previous frame I i-1 Weight , then the pixel points in the current frame image M The pixel value is assigned to the world coordinate point P Otherwise, skip the world coordinate point P The assignment operation; S6, select the next frame image as the current frame and jump to step S3 until all frame images are traversed to obtain the pixel value corresponding to any point cloud in the point cloud data and generate a digital orthophoto map; Step S5 also includes: if the pixel point M Corresponding world coordinate point P In the current frame image I i The weight on Greater than the world coordinate point P In the previous frame I i-1 Weight , then determine whether there is occlusion at the pixel point M in the current frame image when shooting. If there is no occlusion, then change the pixel point M in the current frame image to M The pixel value is assigned to the world coordinate point P If there is occlusion, skip the world coordinate point P The assignment operation; Occlusion judgment method, including: For pixels M Corresponding world coordinate point P , the world coordinate point P The line connecting the camera projection center is recorded as L0, and the world coordinate point P The line connecting the image nadir is recorded as L1; Through the projection relationship, the actual distance of a single pixel on the frame image corresponding to the world coordinate system is obtained. This distance is used as the backtracking step length. Starting from the world coordinate point P, points on L1 are extracted along the L1 direction according to the backtracking step length. For any point (x, y) on the extracted L1, obtain the elevation value Z1 corresponding to (x, y) based on the point cloud data, and calculate the elevation value Z0 corresponding to (x, y) based on the straight line L0; If Z1 is greater than Z0, it means that the world coordinate point P corresponding to the pixel point M is blocked.

2. The method according to claim 1, characterized in that Extract the digital elevation model data blocks that intersect with the current frame image based on the point cloud coordinates and the world coordinates of the four corner vertices of the current frame image, including: Calculate the world coordinates of the four corner vertices of the current frame image and construct the plane bounding box corresponding to the current frame image; Constructing a point cloud bounding box for each digital elevation model data block according to the XY coordinates of the point cloud contained in the digital elevation model data block; Perform an intersection operation on the plane bounding box and any one of the point cloud bounding boxes. If the result is not empty, bind the current frame image to the digital elevation model data block that intersects with it.

3. The method according to claim 1, characterized in that The weight of the world coordinate point corresponding to the pixel point on the current frame image is calculated as: the cosine of the angle between the line connecting the pixel point and the camera projection center and the line connecting the camera projection center and the image bottom point.

4. A device for rapidly generating digital orthophotos based on point clouds, characterized in that: include: Data acquisition module, which obtains point cloud data collected by the radar system and frame images taken by the orthophoto camera; The DEM block module divides the point cloud data into blocks according to the preset size to obtain multiple digital elevation model data blocks; The intersection module extracts the digital elevation model data blocks that intersect with the current frame image based on the point cloud coordinates and the world coordinates of the four corner vertices of the current frame image; The weight calculation module uses the camera imaging model to calculate the world coordinates of each pixel in the current frame image, and calculates the weight of the world coordinate point corresponding to each pixel in the current frame image; The weight judgment and assignment module traverses all the pixels in the current frame image. If the pixel M Corresponding world coordinate point P In the current frame image I i The weight on Greater than the world coordinate point P In the previous frame I i-1 Weight , then the pixel points in the current frame image M The pixel value is assigned to the world coordinate point P Otherwise, skip the world coordinate point P The assignment operation; The digital orthophoto generation module is used to generate a digital orthophoto map after traversing all frame images and obtaining the pixel value corresponding to any point cloud in the point cloud data; The weight judgment and assignment module also includes an occlusion judgment module; The occlusion judgment module is used to judge the pixel point M Corresponding world coordinate point P In the current frame image I i The weight on Greater than the world coordinate point P In the previous frame I i-1 Weight After that, it is determined whether there is any occlusion at the pixel point M in the current frame image when it is shot. If there is no occlusion, the pixel point M in the current frame image is M The pixel value is assigned to the world coordinate point P If there is occlusion, skip the world coordinate point P The assignment operation; The occlusion judgment method of the occlusion judgment module includes: For pixels M Corresponding world coordinate point P , the world coordinate point P The line connecting the camera projection center is recorded as L0, and the world coordinate point P The line connecting the image nadir is recorded as L1; Through the projection relationship, the actual distance of a single pixel on the frame image corresponding to the world coordinate system is obtained. This distance is used as the backtracking step length. Starting from the world coordinate point P, points on L1 are extracted along the L1 direction according to the backtracking step length. For any point (x, y) on the extracted L1, obtain the elevation value Z1 corresponding to (x, y) based on the point cloud data, and calculate the elevation value Z0 corresponding to (x, y) based on the straight line L0; If Z1 is greater than Z0, it means that the world coordinate point P corresponding to the pixel point M is blocked.

5. The device according to claim 4, characterized in that The intersection module includes: The first construction module calculates the world coordinates of the four corner vertices of the current frame image and constructs the plane bounding box corresponding to the current frame image; The second construction module constructs a point cloud bounding box of each digital elevation model data block according to the XY coordinates of the point cloud contained in the digital elevation model data block; The intersection operation and binding module performs an intersection operation on the plane bounding box and any one of the point cloud bounding boxes. If the result is not empty, the current frame image is bounded with the digital elevation model data block that intersects with it.

6. An electronic device, characterized in that: include: Memory for storing computer software programs; A processor is used to read and execute the computer software program, thereby implementing the method for quickly generating a digital orthophoto map based on a point cloud as described in any one of claims 1 to 3.

7. A non-transitory computer-readable storage medium, characterized in that The storage medium stores a computer software program for implementing the method for quickly generating a digital orthophoto map based on a point cloud as described in any one of claims 1 to 3.

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