Target site topographic mapping method and apparatus

Abstract

The present application relates to the field of surveying technology, especially to a target site topographic map measuring method and device. The target site topographic map measuring method of the present application obtains ground image data through unmanned aerial vehicle oblique photogrammetry, and uses landmark points, characteristic points and target site points in the target site positioning process and surveying data to finely correct the aerial survey coordinate elevation data, so that the aerial survey data quality meets the large scale topographic survey requirement; the whole real scene three-dimensional is established through oblique photography, which is intuitive, can query and measure local target site topographic information, meets the structure professional three-dimensional tower site structure design from the whole to the local, and through the verification and correction of the surveying data, the reliability of the aerial survey data is improved, the data quality is ensured, and the correctness of the result is ensured.

Description

Technical Field

[0001] This invention relates to the field of surveying and mapping technology, and in particular to a method and apparatus for measuring topographic maps of target locations. Background Technology

[0002] For overhead transmission line design and wind power generation design, tower site topographic maps and wind turbine site topographic maps are essential technical references for designers. The measurement scale of tower site topographic maps is 1:300, and the measurement scale of wind turbine site topographic maps is 1:500. These topographic maps are characterized by small and discontinuous measurement areas for each tower or wind turbine site, relatively few ground features, and mainly topographic data, especially for hilly and mountainous areas.

[0003] For the survey and design of 220kV and above transmission lines, electrical designers first conduct preliminary tower placement based on aerial or engineering survey plans and cross-sections provided by the surveyors. Then, during the final on-site survey and positioning, multiple professionals, including electrical, structural, geological, hydrological, and surveying specialists, collectively select tower positions on-site, level by level. After the first-level tower position is selected, the next level tower position is determined. For the selected tower position, surveyors need to measure the coordinates and elevations of the tower center, tower legs, and major risk points (which the designers need to record). For tower positions in hilly and mountainous areas, the topography and cross-section of the tower position also need to be measured. Measuring the topography and cross-section of the tower position requires a certain amount of time. In order not to affect the work of other professionals, each positioning operation group is generally equipped with a dedicated tower position measurement team. If the number of surveyors or the number of instruments and equipment cannot meet the requirements for simultaneous positioning and tower position measurement, the needs of surveyors for positioning are generally prioritized. After all tower positions are positioned and measured, the surveyors then conduct separate measurements for each tower individually using engineering surveying methods. Similar to the location selection for power transmission line projects, the micro-site selection of wind power generation involves collaboration among multiple professionals, including structural engineers, geologists, hydrologists, and surveyors. Once the wind turbine location is determined, a large-scale topographic map needs to be taken to design the wind turbine foundation and installation site. Problems in wind power generation micro-site selection surveying are similar to those in power transmission line surveying. Either sufficient surveying personnel and equipment (at least two people) should be provided, or a smaller number of personnel should be used to extend the surveying time.

[0004] Currently, for large-scale, discontinuous, small-area topographic surveying work such as tower site topographic mapping, the common practice is to use the field surveying method to complete the survey in a decentralized manner. The process is shown in the figure below. Topographic points are measured on-site using a surveying GPS receiver or total station. The category and characteristic attribute data of these points are manually recorded. The data is then converted into coordinate data in the transmission line format (such as Daoheng ORG format). Afterwards, topographic mapping software such as CASS is used to draw a topographic map of the topographic survey points for design use. Since the locations of transmission line towers in hilly and mountainous areas are mostly located at high altitudes with complex terrain conditions, making them difficult for vehicles to reach, the surveying relies on manpower to carry the instruments up the mountain. Using a total station requires at least two people to complete the survey: one to operate the total station and the other to run the prism and draw a sketch. Even using the GPS RTK method for transmission line tower site topographic surveying requires at least one person to go up the mountain to complete the tower site topographic surveying work. This work mode is inefficient, time-consuming, labor-intensive, has high field costs and low economic benefits; two surveyors are required to go to the tower site to take measurements, and most of their time and energy are wasted on non-surveying operations such as climbing mountains in difficult and complex terrain; there are high safety risks for personnel and vehicles, and poor safety; there are no obvious markers at or near the tower site, making it inconvenient for later geological surveyors to find the tower location; this method is suitable for traditional two-dimensional tower site structure design, but it is difficult to meet the requirements of modern three-dimensional tower site structure design for measurement data.

[0005] The preliminary micro-site selection of wind farms in hilly and mountainous areas requires the measurement of a 1:500 scale topographic map of the wind turbine location and its vicinity as the basis for the design of the hoisting platform and wind turbine foundation. Currently, the measurement of the wind turbine location and its vicinity in hilly and mountainous areas is generally carried out by engineering surveying, which has the same problems as the measurement of transmission line tower locations.

[0006] With the development of UAV aerial surveying technology, some companies have tried to use conventional UAV aerial surveying technology to conduct tower site topographic surveys. However, after practice, the results are quite different from those of engineering topographic maps, and the results are not good. In particular, in mountainous areas and areas with a lot of shrub vegetation, it is difficult to meet the accuracy requirements of large-scale topographic map measurement by using UAVs equipped with single-camera orthophoto technology. Summary of the Invention

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the problems of low accuracy and failure to meet requirements of the existing UAV aerial survey technology in large-scale, non-continuous, small-area terrain surveying.

[0008] To solve the above-mentioned technical problems, the present invention provides a method for measuring the topographic map of a target location, comprising:

[0009] Acquire ground survey data of control points, landmark points, feature points, and target locations deployed during the positioning process of multiple target locations;

[0010] Use drone oblique photography technology to acquire ground images and POS data;

[0011] Aerial triangulation is performed based on the ground imagery, POS data, ground control points, and landmark survey data. Based on the aerial triangulation results, a real-scene 3D model is created to obtain an aerial survey 3D model.

[0012] The entire terrain area of ​​the target location is divided into segments, and multiple segments of the target location base map are generated based on the survey data of landmarks, feature points and target locations.

[0013] Import the base map of each section of the engineering survey target location and the corresponding section of the aerial survey 3D model into the 3D mapping platform, and extract the landmark point and feature point aerial survey data from each section of the aerial survey 3D model;

[0014] When the error values ​​between the ground survey data and the aerial survey data of landmark points and feature points meet the accuracy requirements, the base map of each segment of the ground survey target location and the corresponding segment of the aerial survey 3D model are matched, and the aerial survey elevation values ​​of the corresponding positions on the aerial survey 3D model are extracted according to the ground survey coordinates of landmark points, feature points and target locations. If the mean square error of the difference between the aerial survey elevation value and the corresponding ground survey elevation value meets the accuracy requirements, the aerial survey data is corrected for elevation to obtain the target aerial survey data.

[0015] A topographic map of the target location is generated based on the aerial survey data of the target.

[0016] Preferably, the image control points are at least one pair of horizontal and vertical markers placed at the beginning, end, and middle of the UAV oblique photography flight path;

[0017] The landmark is located at the center or within the range of each target location and is used as a ground control point or an aerial triangulation check point.

[0018] The feature points include terrain feature points and ground feature points;

[0019] The target location includes the center point of the target location.

[0020] Preferably, the step of performing aerial triangulation based on the ground imagery, the POS data, the ground control points, and the ground landmark survey data, and then performing real-scene 3D modeling based on the aerial triangulation results to obtain the aerial survey 3D model includes:

[0021] Using oblique image processing software, image feature points are automatically extracted and matched based on the solved ground images and POS data to complete relative orientation;

[0022] Import the geodetic data of the control points and perform triangulation. Then, perform bundle constraint joint adjustment of the connection points, control points, and POS values ​​to complete the absolute orientation and obtain the aerial triangulation results.

[0023] The aerial triangulation results are checked using the aforementioned aerial triangulation checkpoints;

[0024] Based on image-based dense matching technology, digital point clouds are obtained according to the aerial triangulation results, and tile segmentation is performed according to the density of the digital point clouds. A piecewise linear model of three-dimensional space is constructed based on the dense point clouds on the tiles.

[0025] Calculate the geometric relationship between each triangular facet on the piecewise linear model in the three-dimensional space and the corresponding ground image region, perform texture registration between the triangular facet and the ground image, and map the registered ground image texture onto the corresponding triangular facet to obtain the aerial survey three-dimensional model.

[0026] Preferably, the step of dividing the entire target location terrain area into segments and generating multiple segments of the target location base map based on landmark points, feature points, and target location survey data includes:

[0027] Based on the survey data of the landmark points, feature points, and target locations, the landmark points, feature points, and target locations are plotted in segments and drawn into the drawing software;

[0028] Connect the centers of each target location with a line and draw the measurement range line of the topographic map of each target location to generate the multi-segment engineering survey target location base map.

[0029] Preferably, if the error value between the ground survey data and the aerial survey data of the landmark points and feature points does not meet the accuracy requirements, the ground survey data of the ground control points are reacquired to perform aerial triangulation and construct an aerial survey 3D model.

[0030] Preferably, matching the base map of each engineering survey target location with the corresponding aerial survey 3D model includes:

[0031] Using the aerial survey coordinates of landmarks and feature points on the 3D aerial survey model as a reference, the base map of each segment of the engineering survey target location is matched to the corresponding segment of the 3D aerial survey model by rotating and translating the engineering survey coordinates of landmarks or feature points, or vice versa.

[0032] Using the coordinates of landmarks and feature points on the ground map of the survey target location as a reference, the 3D aerial survey model of each segment is matched to the corresponding segment of the ground map of the survey target location by rotating and translating the aerial survey coordinates of landmarks or feature points.

[0033] Preferably, if the mean square error of the difference between the aerial survey elevation value and the corresponding engineering survey elevation value does not meet the accuracy requirements, then the mean square error of the difference between the aerial survey elevation value and the engineering survey elevation value is calculated. If the accuracy requirements are met, then the aerial survey data is corrected for elevation to obtain the target aerial survey data.

[0034] Preferably, the elevation correction of the aerial survey data to obtain the target aerial survey data includes:

[0035] The aerial survey 3D model, after being matched with the base map of the engineering survey target location, is vectorized to obtain the vectorized aerial survey data;

[0036] Remove erroneous points where the difference between the aerial survey elevation value and the engineering survey elevation value at the engineering survey coordinates exceeds a preset threshold;

[0037] By employing a point-by-point interpolation method, the difference between the aerial survey elevation value and the engineering survey elevation value at the engineering survey coordinates is allocated, and the vectorized aerial survey data is then corrected for elevation to obtain the target aerial survey data.

[0038] Preferably, generating a target location topographic map based on the target aerial survey data includes:

[0039] The target aerial survey data is transformed by route coordinate transformation, and a triangulation network is constructed using the three-dimensional mapping platform to generate contour lines, delineate ground features, and generate a full-feature target location topographic map.

[0040] The present invention also provides a target location topographic map measuring device, comprising:

[0041] The field data acquisition module is used to acquire the survey data of control points, landmark points, feature points and target points deployed during the positioning process of multiple target locations;

[0042] The ground image data acquisition module is used to acquire ground images and POS data using UAV oblique photography technology;

[0043] The aerial survey 3D model construction module is used to perform aerial triangulation based on the ground images, the POS data, the ground control points and the ground landmark survey data, and to perform real-scene 3D modeling based on the aerial triangulation results to obtain the aerial survey 3D model.

[0044] The target location base map generation module is used to segment the entire target location terrain area and generate multiple segments of target location base maps based on landmark points, feature points, and target location survey data.

[0045] The aerial survey data extraction module is used to import the base map of each section of the engineering survey target location and the corresponding section of the aerial survey 3D model into the 3D mapping platform, and extract the landmark point and feature point aerial survey data from each section of the aerial survey 3D model;

[0046] The aerial survey data correction module is used to match the base map of each segment of the ground survey target location with the corresponding segment of the aerial survey 3D model when the error value between the ground survey data of the landmark point, feature point and target location meets the accuracy requirements. It also extracts the aerial survey elevation value of the corresponding position on the aerial survey 3D model based on the ground survey coordinates of the landmark point, feature point and target location. If the mean square error of the difference between the aerial survey elevation value and the corresponding ground survey elevation value meets the accuracy requirements, the aerial survey data is corrected for elevation to obtain the target aerial survey data.

[0047] The topographic map generation module is used to generate a topographic map of the target location based on the target aerial survey data.

[0048] The technical solution of the present invention has the following advantages compared with the prior art:

[0049] The target location topographic mapping method described in this invention acquires ground image data through UAV oblique photogrammetry. It then uses landmark points, feature points, and target location site survey data from multiple target location positioning processes to finely correct aerial survey coordinate and elevation data, ensuring the aerial survey data quality meets the requirements of large-scale topographic surveying. By establishing a realistic 3D view of the target location through oblique photogrammetry, it provides strong intuitiveness, allows for querying and measuring local tower location topographic information, and meets the structural engineering requirements for 3D tower location structural design from overall to partial. Verification and correction using survey data improves the reliability of the aerial survey data, ensuring data quality and the accuracy of the results. Attached Figure Description

[0050] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0051] Figure 1 This is a flowchart illustrating the implementation of a target location topographic map measurement method provided by the present invention;

[0052] Figure 2 This is a schematic diagram of the structure of a target location topographic map measuring device provided by the present invention. Detailed Implementation

[0053] The core of this invention is to provide a method and apparatus for measuring topographic maps of target locations, which effectively improves the reliability of aerial survey data and meets the accuracy requirements for large-scale topographic map measurement.

[0054] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0055] Please refer to Figure 1 , Figure 1 The flowchart illustrates the implementation of a target location topographic map measurement method provided by this invention; the specific operation steps are as follows:

[0056] S101: Acquire the survey data of control points, landmark points, feature points and target points deployed during the positioning process of multiple target locations;

[0057] Image control points are at least one pair of horizontal and vertical markers placed at the beginning, end, and middle of the UAV oblique photography flight path. The landmarks are located at the center or within the range of each target location and are used as image control points or aerial triangulation checkpoints. The feature points include terrain feature points and ground feature points. The target location includes the target location center point.

[0058] In one embodiment, we use RTK to measure the coordinates and elevations of control points, landmark points, feature points, and target sites to obtain engineering survey data.

[0059] S102: Acquire ground images and POS data using UAV oblique photography technology;

[0060] The UAV adopts a terrain-following flight mode with a post-differential design to perform oblique photography, acquire ground images and POS data along the flight path, and set the forward overlap between 70% and 80% according to the steepness of the terrain, and the lateral overlap between 40% and 50% (multi-flight). After the flight is completed, the images, POS data and other data are checked.

[0061] S103: Perform aerial triangulation based on the ground image, the POS data, the ground control points and the ground landmark survey data, and perform real-scene 3D modeling based on the aerial triangulation results to obtain the aerial survey 3D model;

[0062] Using oblique image processing software, image feature points are automatically extracted and matched based on the solved ground images and POS data to complete relative orientation;

[0063] Import the geodetic data of the control points and perform triangulation. Then, perform bundle constraint joint adjustment of the connection points, control points, and POS values ​​to complete the absolute orientation and obtain the aerial triangulation results.

[0064] The aerial triangulation results are checked using the aforementioned aerial triangulation checkpoints;

[0065] Based on image-based dense matching technology, digital point clouds are obtained according to the aerial triangulation results, and tile segmentation is performed according to the density of the digital point clouds. A piecewise linear model of three-dimensional space is constructed based on the dense point clouds on the tiles.

[0066] Calculate the geometric relationship between each triangular facet on the piecewise linear model in the three-dimensional space and the corresponding ground image region, perform texture registration between the triangular facet and the ground image, and map the registered ground image texture onto the corresponding triangular facet to obtain the aerial survey three-dimensional model.

[0067] S104: Divide the entire target location terrain area into segments, and generate multiple segments of the target location base map based on the landmark points, feature points, and target location survey data;

[0068] Based on the survey data of the landmark points, feature points, and target locations, the landmark points, feature points, and target locations are plotted in segments and drawn into the drawing software;

[0069] Connect the centers of each target location with a line and draw the measurement range line of the topographic map of each target location to generate the multi-segment engineering survey target location base map.

[0070] S105: Import the base map of each section of the engineering survey target location and the corresponding section of the aerial survey 3D model into the 3D mapping platform, and extract the landmark point and feature point aerial survey data from each section of the aerial survey 3D model;

[0071] S106: When the error values ​​between the ground survey data and the aerial survey data of the local landmarks and feature points meet the accuracy requirements, the base map of each segment of the ground survey target location is matched with the corresponding segment of the aerial survey 3D model, and the aerial survey elevation values ​​of the corresponding positions on the aerial survey 3D model are extracted according to the ground survey coordinates of the local landmarks, feature points and target locations. If the mean square error of the difference between the aerial survey elevation value and the corresponding ground survey elevation value meets the accuracy requirements, the aerial survey data is corrected for elevation to obtain the target aerial survey data.

[0072] The process of matching the base map of each section of the engineering survey target location with the corresponding section of the aerial survey 3D model includes:

[0073] Using the aerial survey coordinates of landmarks and feature points on the 3D aerial survey model as a reference, the base map of each segment of the engineering survey target location is matched to the corresponding segment of the 3D aerial survey model by rotating and translating the engineering survey coordinates of landmarks or feature points, or vice versa.

[0074] Using the coordinates of landmarks and feature points on the ground map of the survey target location as a reference, the 3D aerial survey model of each segment is matched to the corresponding segment of the ground map of the survey target location by rotating and translating the aerial survey coordinates of landmarks or feature points.

[0075] The elevation correction of the aerial survey data to obtain the target aerial survey data includes:

[0076] The aerial survey 3D model, after being matched with the base map of the engineering survey target location, is vectorized to obtain the vectorized aerial survey data;

[0077] Remove erroneous points where the difference between the aerial survey elevation value and the engineering survey elevation value at the engineering survey coordinates exceeds a preset threshold;

[0078] In one embodiment, a point-by-point interpolation method is used. By allocating the difference between the aerial survey elevation value and the engineering survey elevation value at the engineering coordinates, the vectorized aerial survey data is corrected for elevation to obtain the target aerial survey data. Aerial survey elevation data correction can employ different methods such as point-by-point interpolation, moving surface fitting, and finite element method.

[0079] S107: Generate a topographic map of the target location based on the aerial survey data of the target.

[0080] In terms of topographic mapping methods, contour lines are generated using the corrected elevation data after elevation correction of aerial survey data, instead of the traditional method of generating contour lines using aerial survey DEM data. The specifics are as follows:

[0081] The target aerial survey data is transformed by route coordinate transformation, and a triangulation network is constructed using the three-dimensional mapping platform to generate contour lines, delineate ground features, and generate a full-feature target location topographic map.

[0082] The target location topographic mapping method described in this invention acquires ground image data through UAV oblique photogrammetry. It then uses landmark points, feature points, and target location site survey data from multiple target location positioning processes to finely correct aerial survey coordinate and elevation data, ensuring the aerial survey data quality meets the requirements of large-scale topographic surveying. By establishing a realistic 3D model of the tower location through oblique photogrammetry, it provides strong intuitiveness, allows for querying and measuring local tower location topographic information, and satisfies the structural engineering requirements for 3D tower location structural design from overall to partial dimensions. Verification and correction using survey data improves the reliability of the aerial survey data, ensuring data quality and the accuracy of the results.

[0083] Based on the above embodiments, if the error value between the ground survey data and the aerial survey data of the landmark points and feature points does not meet the accuracy requirements, the process returns to step S103 to reacquire the ground survey data of the control points for aerial triangulation and construct the aerial survey 3D model.

[0084] Based on the above embodiments, if the mean square error of the difference between the aerial survey elevation value and the corresponding engineering survey elevation value does not meet the accuracy requirements, then the mean square error of the difference between the aerial survey elevation value and the engineering survey elevation value is calculated. If the accuracy requirements are met, then the aerial survey data is corrected for elevation to obtain the target aerial survey data.

[0085] The formula for calculating the mean square error of the difference between the above-mentioned aerial survey elevation values ​​and the corresponding engineering survey elevation values ​​is as follows:

[0086]

[0087] Where, Δ i This represents the difference between the aerial survey elevation value and the engineering survey elevation value at each engineering survey coordinate point, where n represents the total number of engineering survey coordinate points;

[0088] The formula for calculating the mean square error of the difference between the aerial survey elevation value and the engineering survey elevation value is as follows:

[0089]

[0090]

[0091] Where, σ i This represents the difference between the aerial survey elevation value and the engineering survey elevation value at each engineering survey coordinate point.

[0092] like Figure 2 The present invention also provides a target location topographic map measuring device, comprising:

[0093] The field data acquisition module is used to generate the base map of the target location in the engineering survey module. It is used to divide the entire target location terrain area into segments and generate multiple segments of the base map of the target location based on the engineering survey data of landmarks, feature points and target locations.

[0094] The ground image data acquisition module is used to acquire ground images and POS data using UAV oblique photography technology;

[0095] The aerial survey 3D model construction module is used to perform aerial triangulation based on the ground images, the POS data, the ground control points and the ground landmark survey data, and to perform real-scene 3D modeling based on the aerial triangulation results to obtain the aerial survey 3D model.

[0096] The target location base map generation module is used to segment the entire target location terrain area and generate multiple segments of target location base maps based on landmark points, feature points, and target location survey data.

[0097] The aerial survey data extraction module is used to import the base map of each section of the engineering survey target location and the corresponding section of the aerial survey 3D model into the 3D mapping platform, and extract the landmark point and feature point aerial survey data from each section of the aerial survey 3D model;

[0098] The aerial survey data correction module is used to match the base map of each segment of the ground survey target location with the corresponding segment of the aerial survey 3D model when the error value between the ground survey data of the landmark point, feature point and target location meets the accuracy requirements. It also extracts the aerial survey elevation value of the corresponding position on the aerial survey 3D model based on the ground survey coordinates of the landmark point, feature point and target location. If the mean square error of the difference between the aerial survey elevation value and the corresponding ground survey elevation value meets the accuracy requirements, the aerial survey data is corrected for elevation to obtain the target aerial survey data.

[0099] The topographic map generation module is used to generate a topographic map of the target location based on the target aerial survey data.

[0100] The aforementioned target location topographic mapping device can be applied to large-scale, non-continuous, small-area topographic mapping, such as topographic mapping of transmission line tower locations and wind turbine locations.

[0101] Based on the above embodiments, this embodiment provides a specific application of topographic map measurement for transmission line tower locations:

[0102] S201: First, the flight path and flight altitude are designed. The UAV oblique photography flight path adopts a single flight path design along the center line of the route. By analyzing the horizontal cross section, the flight altitude is designed according to the tower elevation along the route. If the tower elevation fluctuates greatly, a variable altitude flight design is adopted to ensure that the ground resolution of 70% of the tower positions is not less than 3cm, and the relative flight altitude is within the range of 100-150m.

[0103] S202: During the final survey and positioning of the route, 1-2 landmark points are set up at the center of the tower or within the tower location. The landmark points are used as image control points or checkpoints. Before the oblique photogrammetry operation, 2 level and elevation markers are set up at each end of the route. At least one pair of level and elevation markers are set up in the middle of the route according to the length of the route as image control points. RTK is used to measure the coordinates and elevations of the image control points and landmark points.

[0104] S203: The UAV adopts a post-differential flight mode to perform oblique photography. Under clear weather conditions with wind force not exceeding level 4, ground images are acquired along the designed flight path, with the flight path overlap set at 80%. For areas with large differences in tower elevation, a variable altitude flight mode is adopted, and the flight altitude is adjusted according to the ground elevation. Variable altitude flight can ensure that the resolution and overlap of the acquired oblique images remain consistent. After the flight is completed, the acquired images, POS data, etc. are processed as necessary, and their quality is checked.

[0105] S204: Aerial triangulation is performed using professional oblique image processing software (such as Context Capture, hereinafter referred to as CC). The calculated POS data, images, and camera files are imported into the software for automatic extraction and matching of image feature points to complete relative orientation. Then, the image control point results are imported for adjustment. Bundle method constraint joint adjustment of tie points, control points, and POS values ​​is completed to achieve absolute orientation. Finally, high-precision tie points and interior and exterior orientation elements of the images are obtained. Landmarks near the tower measured during the positioning process can be used partly as image control points and partly as aerial triangulation quality check points.

[0106] S205: Based on aerial triangulation results, realistic 3D modeling is performed using professional processing software such as CC. First, high-precision digital point clouds are obtained using dense matching techniques on the images. The point cloud is then segmented into tiles according to its density, and TIN models of varying fineness are constructed using the dense point clouds on the tiles. After constructing the TIN model, the geometric relationship between each triangular facet and its corresponding image region is calculated to register the irregular triangular mesh and the texture image. The registered texture is then mapped onto the triangular facets to complete the texturing, finally generating a realistic 3D model.

[0107] S206: Divide the entire line into several segments based on information such as flight count, tension section, and tower elevation. Plot the tower locations (i.e., tower center and center points of each tower leg), terrain feature points, and landmark points measured during the positioning process into professional drawing software. Connect the centers of each tower location and draw the measurement range of the topographic map of each tower location, generating the engineering survey base map of each tower location segment by segment.

[0108] S207: Load a section of the aerial survey 3D model OSGB and the corresponding section of the tower location survey base map into professional 3D mapping platforms such as ESP and Mapmatrix, and use the functions of the 3D mapping platform to query, measure, collect, and extract the terrain feature information on the aerial survey 3D model.

[0109] S208: Using the 3D mapping platform, collect and extract the coordinates and elevations of landmark points and prominent feature points within the base map area on the aerial survey 3D model, and generate data files. Using the 3D mapping platform, measure the differences between the aerial and ground survey positions of landmark points and feature points on the 3D model, or compare the ground survey data and aerial survey data of landmark points and feature points, and calculate the differences in coordinates and elevations. If the mean square error of the coordinate difference is no greater than ±0.3m, and the mean square error of the elevation difference is no greater than ±0.3m, proceed to the next step. If this accuracy requirement is not met, return to step S204 to reacquire ground survey data of the control points and perform aerial triangulation.

[0110] S209: Using the locations of landmarks or feature points on the aerial survey 3D model as a reference, the engineering survey base map of each tower location is matched to the aerial survey 3D model through rotation and translation using landmarks or feature points. Utilizing the 2D / 3D synchronization function of the mapping platform, the elevation values ​​of the tower center, tower leg centers, feature points, checkpoints, and other engineering survey locations on the positioning base map are manually extracted from the aerial survey 3D model. After collection, the corresponding elevation data files are output. The aerial survey elevation values ​​at the tower center, the centers of each tower leg, feature points, checkpoints, and other survey locations are compared with the surveyed elevation values. The mean square error of the elevation difference is calculated, and it is determined whether the mean square error is no greater than ±0.3m. If the mean square error meets the requirement, it indicates that the aerial survey data is relatively reliable, and the aerial survey elevation data can be used to produce a tower location topographic map after correction. If the mean square error does not meet the requirement, further analysis of the difference between the aerial survey and the surveyed data is conducted. The analysis of the difference between the aerial survey and the surveyed data is as follows: Based on the high relative accuracy of elevation in oblique photogrammetry, the mean square error of the difference between the oblique photogrammetry elevation and the surveyed elevation at the survey location is analyzed. If the mean square error of the difference is within ±0.3m, it indicates that the oblique photogrammetry data may have systematic errors, and after correction, it can be used as elevation data for the topographic map. If the mean square error of the difference exceeds ±0.3m, it indicates that the aerial survey results at that location are unreliable, and this method is not used to produce a tower location topographic map.

[0111] S210: In a 3D mapping platform (such as ESP, Mapmatrix, and other professional processing software), based on the aerial survey 3D model matched with the engineering survey base map, the platform's 2D and 3D synchronization function is used to collect terrain data in a 2D and 3D linkage mode. Real terrain and landform features are acquired in real time and output as data files to obtain vectorized aerial survey data within the tower location area. Elevation correction is performed on the vectorized aerial survey data. Based on the difference between the aerial survey elevation and the engineering survey elevation at the engineering survey location, obvious error points with large differences are eliminated. Aerial survey elevation data correction can be achieved using different methods such as point-by-point interpolation, moving surface fitting, and finite element method. By allocating the difference between the engineering survey elevation and the aerial survey elevation, elevation correction of the vectorized aerial survey data is realized.

[0112] S211: After elevation correction, the aerial survey vector data undergoes a line coordinate transformation using coordinate transformation software to convert the grid coordinate data into line coordinate data. The transformed aerial survey data is then imported into a mapping platform. The platform's functions are used to construct a triangulation network, generate contour lines, and delineate the features within the tower location area. Alternatively, the topographic map of features in the grid coordinate system can be transformed to the current line coordinate system to generate a full-feature tower location topographic map. The topographic map features are then refined according to specifications, with annotations, legends, and map frame icons added, resulting in a final deliverable submitted for structural engineering use.

[0113] The steps for applying this method to topographic surveying of wind turbines and hoisting platforms are basically the same as those for topographic mapping of tower sites in overhead transmission line projects. The difference lies in that the flight path is designed based on the layout and elevation of the wind turbine sites. According to the flight path design, all wind turbine sites in the wind farm are divided into several groups, and a base map of each group is generated. The topographic maps of wind turbine sites and hoisting platforms do not require line coordinate transformation of the aerial survey vector data. Furthermore, since the required scale for wind turbine site mapping is 1:500, there is no elevation error requirement like for tower site topographic maps. The difference between the elevation of the ground survey and the aerial survey can be relaxed to no more than ±0.3–±0.7m depending on the terrain conditions. This technical method is more widely used in topographic mapping of wind turbine sites. The specific steps are as follows:

[0114] S301: First, the flight path and altitude are designed. Based on the wind turbine locations initially selected in the feasibility study stage, a single-line or multi-line flight design is adopted to ensure that the ground resolution of 70% of the area is not less than 5cm and the relative flight altitude is within the range of 130-180m.

[0115] S302: During the micro-site selection of wind turbine locations, 1-2 landmark points are set up in the vicinity of the center of the wind turbine location. The landmark points are used as image control points or checkpoints. Before the oblique photogrammetry operation, the image control points are set up first. For single-line design, 2 level and elevation markers are set up at each end of the line. In the middle of the line, no less than 1 pair of level and elevation markers are set up according to the length of the line. For multi-line design, the image control points are set up according to the requirements of the regulations. RTK is used to measure the coordinates and elevations of the image control points and landmark points.

[0116] S303: The UAV adopts a post-differential flight mode to perform oblique photography. Under clear weather conditions with wind force not exceeding level 4, it acquires ground images along the designed flight path with a forward overlap of 80%. For areas with large differences in wind turbine elevation, a variable altitude flight mode is adopted to adjust the flight altitude according to the ground elevation. Variable altitude flight can ensure that the resolution and overlap of the acquired oblique images remain consistent. After the flight is completed, the acquired images and POS data are processed as necessary and checked for compliance.

[0117] S304: Same as S204.

[0118] S305: Same as S205.

[0119] S306: Based on the number of flights or the local concentrated area of ​​wind turbines, the measurement points such as landmarks, wind turbine locations, and control points measured on-site during the micro-site selection process are plotted in professional drawing software such as CASS. The centers of each wind turbine location are connected, and the measurement range of the topographic map of each wind turbine location is drawn, generating the base map of the wind turbine location segment by segment.

[0120] S307: Same as S207.

[0121] S308: Utilize the 3D mapping platform to collect and extract the coordinates and elevations of landmark points and prominent feature points within the base map area on the aerial survey 3D model, and generate data files. Using the 3D mapping platform, measure the differences in the aerial and field survey positions of landmark points and feature points on the 3D model, or compare the field survey data and aerial survey data of landmark points and feature points, calculating the differences in coordinates and elevations. The mean square error of the difference in plane and elevation between aerial and field surveys for landmark points and feature points should not exceed ±0.3m in flat areas and not exceed ±0.7m in mountainous areas. If the mean square error meets this requirement, proceed to the next step; otherwise, return to step S204 to remeasure the external control points and perform aerial triangulation.

[0122] S309: Based on the locations of landmarks or feature points on the wind turbine site survey base map, the landmarks or feature points on the aerial survey 3D model are rotated and translated to their corresponding positions on the survey base map. Using the 2D / 3D synchronization function of the mapping platform, the elevation values ​​of the feature points, landmarks, etc., measured during micro-site selection are manually extracted from the real-world model. After data collection, the corresponding elevation data files are output. The aerial survey elevation values ​​and the survey elevation values ​​at the feature points, landmarks, etc., are then compared, and the mean square error of the elevation difference is calculated. The difference is then assessed to determine if it meets the following requirements: in flat areas, the mean square error of the horizontal and vertical elevation difference is no greater than ±0.3m; in mountainous areas, the mean square error of the horizontal and vertical elevation difference is no greater than ±0.7m. If the mean square error of the difference meets the requirements, it indicates that the aerial survey data is relatively reliable. After correction, the aerial survey elevation data can be used to produce wind turbine site topographic maps. If the mean square error of the difference does not meet the requirements, further analysis of the difference patterns between the aerial and engineering survey data is conducted. This analysis is based on the high relative accuracy of elevation data obtained through oblique photogrammetry. The mean square error of the difference between the aerial and engineering elevations at the engineering survey location is analyzed. If the mean square error of the difference meets the following criteria: no more than ±0.3m in flat areas and no more than ±0.7m in mountainous areas, it indicates that the aerial survey data may have systematic errors. After correction, the aerial survey data can be used as elevation data for topographic maps. If the mean square error of the difference does not meet the above requirements, it indicates that the aerial survey results at that location are unreliable, and this method should not be used to produce wind turbine site topographic maps.

[0123] S310: Same as S210.

[0124] S311: Import the corrected aerial survey data into the mapping platform, use the mapping platform's functions to construct a triangulation network, generate contour lines, delineate the ground features within the wind turbine location area, generate a full-feature tower location topographic map, then refine the topographic map features according to specifications, add annotations, legends, map frame icons, and other elements, and generate a formal result for submission to the design profession.

[0125] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for measuring the topographic location of a target, characterized in that, include: The method acquires ground survey data of image control points, landmark points, feature points, and target locations deployed during the positioning of multiple target locations. The image control points are at least one pair of horizontal and vertical markers deployed at the beginning, end, and middle of the UAV oblique photography flight path. The landmark points are located at the center or within the range of each target location and are used as image control points or aerial triangulation checkpoints. The feature points include terrain feature points and ground feature points. The target location includes the center point of the target location. Ground imagery and POS data were acquired using drone oblique photography technology, including: Oblique photography was performed using a post-differential UAV ground-following flight mode to acquire ground images and POS data along the flight path; Aerial triangulation is performed based on the ground imagery, POS data, ground control points, and landmark survey data. Based on the aerial triangulation results, a real-scene 3D model is created to obtain an aerial survey 3D model. The entire terrain area of ​​the target location is divided into segments, and multiple base maps of the target location are generated based on landmark points, feature points, and target location survey data, including: Based on the survey data of the landmark points, feature points, and target locations, the landmark points, feature points, and target locations are plotted in segments and drawn into the drawing software; Connect the centers of each target location with a line and draw the measurement range line of the topographic map of each target location to generate the multi-segment engineering survey target location base map; Import the base map of each section of the engineering survey target location and the corresponding section of the aerial survey 3D model into the 3D mapping platform, and extract the landmark point and feature point aerial survey data from each section of the aerial survey 3D model; If the error values ​​between the ground survey data and the aerial survey data for landmark points and feature points meet the accuracy requirements, then the base map of each segment of the ground survey target location and the corresponding segment of the aerial survey 3D model will be matched, including: Using the aerial survey coordinates of landmarks and feature points on the 3D aerial survey model as a reference, the base map of each segment of the engineering survey target location is matched to the corresponding segment of the 3D aerial survey model by rotating and translating the engineering survey coordinates of landmarks or feature points, or vice versa. Based on the coordinates of landmarks and feature points on the base map of the engineering survey target location, each segment of the aerial survey 3D model is matched to the corresponding segment of the base map of the engineering survey target location by rotating and translating the aerial survey coordinates of landmarks or feature points. Based on the coordinates of landmarks, feature points, and target locations, the aerial survey elevation values ​​on the 3D aerial survey model are extracted. If the mean square error of the difference between the aerial survey elevation value and the corresponding engineering survey elevation value meets the accuracy requirements, or if the mean square error of the difference between the aerial survey elevation value and the engineering survey elevation value meets the accuracy requirements, then the aerial survey data is subjected to elevation correction to obtain the target aerial survey data, including: The aerial survey 3D model, after being matched with the base map of the engineering survey target location, is vectorized to obtain the vectorized aerial survey data; Remove erroneous points where the difference between the aerial survey elevation value and the engineering survey elevation value at the engineering survey coordinates exceeds a preset threshold; By employing a point-by-point interpolation method, the difference between the aerial survey elevation value and the engineering survey elevation value at the engineering survey coordinate is allocated, and the vectorized aerial survey data is then corrected for elevation to obtain the target aerial survey data. Generate a topographic map of the target location based on the aerial survey data, including: The target aerial survey data is transformed by route coordinate transformation, and a triangulation network is constructed using the three-dimensional mapping platform to generate contour lines, delineate ground features, and generate a full-feature target location topographic map.

2. The target location topographic map measurement method according to claim 1, characterized in that, The aerial triangulation based on the ground imagery, POS data, ground control points, and landmark survey data, followed by the creation of a real-scene 3D model based on the aerial triangulation results, yields the following aerial survey 3D model: Using oblique image processing software, image feature points are automatically extracted and matched based on the solved ground images and POS data to complete relative orientation; Import the geodetic data of the control points and perform triangulation. Then, perform bundle constraint joint adjustment of the connection points, control points, and POS values ​​to complete the absolute orientation and obtain the aerial triangulation results. The aerial triangulation results are checked using the aforementioned aerial triangulation checkpoints; Based on image-based dense matching technology, digital point clouds are obtained according to the aerial triangulation results, and tile segmentation is performed according to the density of the digital point clouds. A piecewise linear model of three-dimensional space is constructed based on the dense point clouds on the tiles. Calculate the geometric relationship between each triangular facet on the piecewise linear model in the three-dimensional space and the corresponding ground image region, perform texture registration between the triangular facet and the ground image, and map the registered ground image texture onto the corresponding triangular facet to obtain the aerial survey three-dimensional model.

3. The target location topographic map measurement method according to claim 1, characterized in that, If the error value between the ground survey data and the aerial survey data of the landmark points and feature points does not meet the accuracy requirements, the ground survey data of the ground control points will be reacquired to perform aerial triangulation and construct the aerial survey 3D model.

4. A target location topographic map measuring device, characterized in that, The apparatus implements the method as described in claim 1, the apparatus comprising: The field data acquisition module is used to acquire the survey data of control points, landmark points, feature points and target points deployed during the positioning process of multiple target locations; The ground image data acquisition module is used to acquire ground images and POS data using UAV oblique photography technology; The aerial survey 3D model construction module is used to perform aerial triangulation based on the ground images, the POS data, the ground control points and the ground landmark survey data, and to perform real-scene 3D modeling based on the aerial triangulation results to obtain the aerial survey 3D model. The target location base map generation module is used to segment the entire target location terrain area and generate multiple segments of target location base maps based on landmark points, feature points, and target location survey data. The aerial survey data extraction module is used to import the base map of each section of the engineering survey target location and the corresponding section of the aerial survey 3D model into the 3D mapping platform, and extract the landmark point and feature point aerial survey data from each section of the aerial survey 3D model; The aerial survey data correction module is used to match the base map of each segment of the ground survey target location with the corresponding segment of the aerial survey 3D model when the error value between the ground survey data of the landmark point, feature point and target location meets the accuracy requirements. It also extracts the aerial survey elevation value of the corresponding position on the aerial survey 3D model based on the ground survey coordinates of the landmark point, feature point and target location. If the mean square error of the difference between the aerial survey elevation value and the corresponding ground survey elevation value meets the accuracy requirements, the aerial survey data is corrected for elevation to obtain the target aerial survey data. The topographic map generation module is used to generate a topographic map of the target location based on the target aerial survey data.

Images