Large-scale topographic map surveying and mapping method based on oblique photography and airborne LiDAR

Abstract

The invention discloses a large-scale topographic map surveying and mapping method based on oblique photography and airborne LiDAR. The large-scale topographic map surveying and mapping method comprises the following steps: S1, data acquisition; s2, carrying out three-dimensional modeling; s3, collecting ground features and landforms; s4, carrying out LiDAR point cloud classification and contour line data production; s5, data fusion; and S6, field annotation and data editing. According to the scheme, on the basis of oblique photography and airborne LiDAR topographic map surveying and mapping, ground feature and landform data (except contour lines) collected on a three-dimensional model are fused, contour line data are produced on the basis of LiDAR point cloud, large-scale topographic map surveying and mapping can be completed in combination with field plotting, and surveying and mapping efficiency and accuracy can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of topographic mapping, and in particular to a large-scale topographic mapping method. Background Art

[0002] At present, for some topographic mapping operations, they are usually based on the collection of image data by aerial photogrammetry, and the work is carried out through the operation modes of indoor positioning and collection, outdoor qualitative analysis, etc. However, the traditional large-scale topographic mapping has high labor intensity, long field measurement time, and meticulous and tedious work. There are many links that are prone to errors, and the quality requirements of the operators are high. In addition, when collecting data in the office, it is necessary to wear stereo glasses for a long time to collect data, which also makes the labor intensity of the indoor collectors high. As mentioned above, the efficiency of topographic mapping is low.

[0003] In addition, in some areas with lush surface vegetation, aerial photogrammetry is difficult to accurately obtain data such as surface contour lines due to the obstruction of vegetation, resulting in low accuracy in surveying and mapping topographic maps. Summary of the invention

[0004] The purpose of the present invention is to provide a large-scale topographic mapping method based on oblique photography and airborne LiDAR, which can improve the mapping efficiency and accuracy.

[0005] To achieve the above purpose, a large-scale topographic mapping method based on oblique photography and airborne LiDAR is provided, which includes: S1. Data collection: Oblique photography and airborne LiDAR data acquisition are performed simultaneously on the same photography platform; S2. 3D modeling: Divide the oblique photography images into image groups; use the regional network joint adjustment without ground control to deal with the geometric deformation and occlusion between the images; import the image control points into the engineering block and measure the ground image control points on the image; perform aerial triangulation based on the bundle method regional network adjustment to obtain the exterior orientation elements of the oblique image data at the time of aerial photography, and obtain the coordinates of the encrypted points in the image in the object space coordinate system; based on the results of aerial triangulation, reconstruct the three-dimensional model based on the oblique image data; S3. Collection of landforms and features: Based on the reconstructed 3D model, collect the elevation of objects, landforms, and elevation points; S4, LiDAR point cloud classification and contour data production: Obtain DEM data based on LiDAR point cloud data, and derivate contour data based on the acquired DEM data; S5. Data fusion: The layers contained in the objects and landforms collected by S3 and the contour data obtained by S4 are merged into one data to obtain topographic map data; S6. Field survey and data editing: Through field survey and mapping, field data is obtained, topographic map data is verified and modified, and after being sorted out, topographic mapping results are formed.

[0006] According to the large-scale topographic mapping method based on oblique photography and airborne LiDAR, in S2, dividing the oblique photography images into image groups includes: dividing the images taken by the same camera and having the same internal orientation into one image group.

[0007] According to the large-scale topographic mapping method based on oblique photography and airborne LiDAR, in S2, image control points are imported into the engineering block, and in the step of measuring ground image control points on the image, the thorn points are distributed on the photos of multiple flight strips.

[0008] According to the large-scale topographic mapping method based on oblique photography and airborne LiDAR, in S2, performing aerial triangulation based on bundle block adjustment includes the following steps: Feature point extraction: extract the characteristic points in each image and mark and name them; Feature point matching: associate points with the same name in different images; Bundle method block adjustment; The adjustment equation is as follows: Where X1 is the correction number of the exterior orientation element and the encrypted point coordinates; P1 is the weight of the image point observation value; X2 is the correction number of the control point coordinates; P2 is the weight of the control point coordinate observation value; X3 is the correction number of the exterior orientation element; P3 is the weight of the exterior orientation element; X4 is the self-calibration parameter; P4 is the weight of the self-calibration parameter; A1, A2, A3, A4 are the coefficient matrices of the error equation; E1, E2, E3, E4 are the unit matrices; L1, L2, L3, L4 are the image point observation value vectors; V1, V2, V3, V4 are the error result matrices.

[0009] According to the large-scale topographic mapping method based on oblique photography and airborne LiDAR, in S2, when the same-name points cannot be accurately matched or the mirror reflections interfere with the same-name points, the three-dimensional production software Reconstruction Master is used to automatically generate a real-scene three-dimensional model; when there are deviations in the water surface material part and the small ground object part, the DPmodeler system is used to modify the local geometric model errors of the automatically generated three-dimensional model.

[0010] According to the large-scale topographic mapping method based on oblique photography and airborne LiDAR, in S3, based on the reconstructed three-dimensional model, the steps of collecting the elevations of objects, landforms, and elevation points are as follows: the surface and linear spatial objects and landforms are collected directly on the three-dimensional model; if the accuracy of the three-dimensional model cannot meet the requirements, the oblique images are combined for collection; for the collection of point-like spatial objects, the main and secondary oblique images can be retrieved and the point positions can be determined using the principle of forward intersection; the elevation of the elevation point is the spatial three-dimensional data obtained by pixel-by-pixel matching based on the oblique photography measurement software, and the elevation points are collected in open areas without trees or tall buildings.

[0011] According to the large-scale topographic mapping method based on oblique photography and airborne LiDAR, in S4, in the step of obtaining DEM data based on LiDAR point cloud data: The airborne LiDAR point cloud data is solved using the differential GNSS data and IMU data output by the inertial navigation system to obtain real-time position data; Use LiDAR 360 software to pre-process the LiDAR point cloud and filter out points that are obviously below the ground and points that are obviously above the ground; Create a new project in SCOP++ software, add data layer in Add model overlay window, input layer name, obtain ground points, interpolate to generate DEM data, and perform point cloud classification; Check and set the DSM grid size, and select Robust filtering and LiDAR Defalt Strong template strategies; In the selected LiDAR Defalt Strong template strategy, set the cell mesh size in Thinout step3, Thinoutstep7, and Thinout step11 to perform thinning; Perform filtering. After filtering, the point cloud is layered into LowPoint, Building, HighVegetationg, MediumVegetationg, LowVegetation, GroundSynthetic, and Ground layers, and the ground point Ground layer is retained; Modify the sampling grid size and bridge node distance in FillvoidAreas Step 13 to fill the DEM data grid.

[0012] According to the large-scale topographic mapping method based on oblique photography and airborne LiDAR, in S4, in the step of derivation of contour data based on the acquired DEM data: Use ArcGis software to invert contour data: open ArcToolBox 3D Analyst ToolsRasterSurface Contour, set parameters in the pop-up dialog box, output file type as *.shp, and generate preliminary contour data; Contour line smoothing: Open ArcToolbox Cartography Tools Generalization SmoothLine, set parameters according to the terrain, and smooth the contour lines; Add fields: Add fields GB and ELEV, where the data type of GB is Text (9) and ELEV is Double; enter the calculation formula GB code in the GB column, run the field operator in the ELEV column, and assign its value to the ELEV attribute item; Among them, for the inversely derived contour data, if there is distortion of contour lines after filtering in areas with dense vegetation, if the filtering is not completely based on ground points, or if the relationship between ridges and contour lines is unreasonable, modifications will be made in combination with the three-dimensional model.

[0013] According to the large-scale topographic mapping method based on oblique photography and airborne LiDAR, in S6, in the step of obtaining field data through field surveying and mapping: for linear features blocked by trees, independent features of small areas, and features that are difficult to interpret and judge in the field, information is obtained through field surveying and mapping; place names, pipeline directions, and pipeline names are obtained through field surveying and mapping.

[0014] Beneficial effects: In the above scheme, based on oblique photography and airborne LiDAR topographic mapping, the collected land features and landform data (except contour lines) on the 3D model are integrated, and contour line data is produced based on LiDAR point cloud. Combined with field surveying, large-scale topographic mapping can be completed; Compared with the traditional aerial photogrammetry collection mode that requires wearing stereo glasses, this solution reduces the labor intensity of indoor data collection personnel and improves data collection efficiency; it breaks the traditional working mode of indoor positioning and outdoor qualitative analysis, and combined with high-definition three-dimensional models, most of the attributes of land objects can be directly extracted through indoor work, reducing the workload of outdoor mapping and greatly improving the production efficiency of topographic mapping; Airborne laser LiDAR has the technical characteristics of high efficiency, precision and strong penetration. It is well suited for large-scale topographic surveying in areas with dense vegetation and can improve the accuracy of surveying and mapping. The overall efficiency of topographic mapping technology based on oblique photography and airborne LiDAR is better than traditional surveying and mapping methods.

[0015] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention is further described below in conjunction with the accompanying drawings and embodiments; Figure 1 is a flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0017] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0018] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0019] Reference Figure 1 , a large-scale topographic mapping method based on oblique photography and airborne LiDAR includes the following steps: S1. Data collection: Oblique photography and airborne LiDAR data acquisition are performed simultaneously on the same photography platform; S2. 3D modeling: Divide the oblique photography images into image groups; use the regional network joint adjustment without ground control to deal with the geometric deformation and occlusion between the images; import the image control points into the engineering block and measure the ground image control points on the image; perform aerial triangulation based on the bundle method regional network adjustment to obtain the exterior orientation elements of the oblique image data at the time of aerial photography, and obtain the coordinates of the encrypted points in the image in the object space coordinate system; based on the results of aerial triangulation, reconstruct the three-dimensional model based on the oblique image data; S3. Collection of landforms and features: Based on the reconstructed 3D model, collect the elevation of objects, landforms, and elevation points; S4, LiDAR point cloud classification and contour data production: Obtain DEM data based on LiDAR point cloud data, and derivate contour data based on the acquired DEM data; S5. Data fusion: All layers contained in the ground objects and landforms collected by S3 and the contour data obtained by S4 are merged into one data to obtain topographic map data; S6. Field survey and data editing: Through field survey and mapping, field data is obtained, topographic map data is verified and modified, and after being sorted out, topographic mapping results are formed.

[0020] Specifically, in S1, the same drone is equipped with oblique photography equipment and airborne LiDAR equipment to obtain two types of data in the same flight. Among them, oblique photography can obtain multiple perspective images and obtain all-round information on ground objects due to the increase in the number of lenses, which is an important part of the three-dimensional model data construction work; airborne LiDAR has the characteristics of penetrability, all-weather, and high precision, and can obtain three-dimensional coordinate data of ground objects, and its results are in the form of point clouds.

[0021] In S2, the oblique photography images are divided into image groups, specifically including: images taken by the same camera and having the same internal orientation (image size, sensor size, focal length, etc.) are divided into one image group. The oblique photography data is processed by regional network joint adjustment without ground control to solve the geometric deformation and occlusion problems between images.

[0022] In S2, the image control points are imported into the engineering block, and in the step of measuring the ground image control points on the image, the puncture points are generally distributed on the photos of multiple flight strips as much as possible.

[0023] In S2, the aerial triangulation based on bundle block adjustment specifically includes the following steps: Feature point extraction: extract the characteristic points in each image and mark and name them; Feature point matching: associate points with the same name in different images; The bundle method is used for block adjustment; The adjustment equation is as follows: Where X1 is the correction number of the exterior orientation element and the encrypted point coordinates; P1 is the weight of the image point observation value; X2 is the correction number of the control point coordinates; P2 is the weight of the control point coordinate observation value; X3 is the correction number of the exterior orientation element; P3 is the weight of the exterior orientation element; X4 is the self-calibration parameter; P4 is the weight of the self-calibration parameter; A1, A2, A3, A4 are the coefficient matrices of the error equation; E1, E2, E3, E4 are the unit matrices; L1, L2, L3, L4 are the image point observation value vectors; V1, V2, V3, V4 are the error result matrices.

[0024] After aerial triangulation, the exterior orientation elements of the oblique image data at the time of aerial photography can be obtained, and the coordinates of the encrypted points in the image in the object space coordinate system can be obtained. Based on the results of aerial triangulation, a three-dimensional model based on oblique image data can be reconstructed (specifically, the reconstruction master software can be used to automatically map the real scene texture to complete the automatic construction of the three-dimensional model).

[0025] In S2, when the same-name points cannot be accurately matched or the mirror reflection interferes with the same-name points, the 3D production software Reconstruction Master is used to automatically generate a real-scene 3D model; when there are deviations in the water surface material part and the small ground object part, the DPmodeler system is used to modify the local geometric model errors of the automatically generated 3D model.

[0026] In S3, in the step of "collecting the elevation of objects, landforms, and elevation points based on the reconstructed 3D model", the topographic map data collection based on the real-life 3D model of oblique photography can be directly measured on the 3D model, or the image can be automatically selected from multiple perspectives, and oblique images can be used for forward intersection mapping to meet the requirements of large-scale high-precision mapping. Specifically: The 3D model is very accurate. The collection of surface and linear spatial features, such as houses, balconies, eaves, walls, fences, ridges, steep slopes, etc., can be directly collected on the 3D model. If the accuracy of the 3D model cannot meet the needs, it can be collected in combination with oblique images. For the collection of point-like spatial features such as power lines, street lights, road signs, etc., the main and secondary oblique images can be retrieved and the point positions can be accurately determined using the principle of forward intersection. The elevation of the elevation point is the spatial 3D data obtained by pixel-by-pixel matching based on the oblique photogrammetry software. The collection of elevation points should be collected as much as possible in open areas without trees or tall buildings.

[0027] In S4, in the step of "obtaining DEM data based on LiDAR point cloud data": The airborne LiDAR point cloud data is solved using the differential GNSS data and IMU data output by the inertial navigation system to obtain real-time position data; Use LiDAR 360 software to pre-process the LiDAR point cloud and filter out points that are obviously below the ground and points that are obviously above the ground; Create a new project in SCOP++ software, add data layer in Add model overlay window, input layer name, obtain ground points, interpolate to generate DEM data, and perform point cloud classification; Check and set the DSM grid size, and select Robust filtering and LiDAR Defalt Strong template strategies; In the selected LiDAR Defalt Strong template strategy, set the cell grid size in Thinout step3, Thinoutstep7, and Thinout step11 to perform thinning. The smaller the grid size, the lighter the filtering effect. The larger the grid size, the stronger the filtering effect, but there may be feature loss. Perform filtering. After filtering, the point cloud is divided into LowPoint, Building, HighVegetationg, MediumVegetationg, LowVegetation, GroundSynthetic, and Ground layers. Only the Ground layer of ground points needs to be retained. Modify the sampling grid size and bridge node distance in FillvoidAreas Step 13 to fill the DEM data grid.

[0028] In S4, in the step of "deriving contour data from acquired DEM data", the contour data production is derived from the DEM data obtained based on point cloud classification in the ArcGis software. Specifically: Use ArcGis software to invert contour data: open ArcToolBox 3D Analyst ToolsRasterSurface Contour, set the corresponding parameters in the pop-up dialog box, output file type as *.shp, and generate preliminary contour data; Contour line smoothing: Open ArcToolbox Cartography Tools Generalization SmoothLine, set the corresponding parameters according to the terrain, and smooth the contour lines; Add fields: Add fields GB and ELEV, where the data type of GB is Text (9) and ELEV is Double; enter the calculation formula GB code in the GB column, run the field operator in the ELEV column, and assign its value to the ELEV attribute item; Among them, for the inversely derived contour data, such as the distortion of contour lines after filtering in dense vegetation areas, the failure to filter completely according to ground points, and the unreasonable relationship between ridges and contour lines, modifications are made in combination with the three-dimensional model.

[0029] In S5, the objects, landforms (except contour lines) and all layers included in the contour line data obtained in the above steps are merged into one data to obtain complete topographic map data.

[0030] In S6, in the step of "obtaining field data through field survey and mapping": For linear features blocked by trees, small independent features, and features that are difficult to interpret and judge in-house, information (including the location, attributes, and other information of the feature elements) is obtained through field mapping; place names, pipeline directions, and pipeline names are obtained through field mapping.

[0031] In the step of "forming topographic map surveying and mapping results after sorting", based on the field survey and mapping results, the linear features blocked by trees, small-area independent features, features that are difficult to interpret and judge internally, place names, pipeline directions, pipeline names, etc. involved in the topographic map data are verified and modified, and the results are edited according to the project requirements, and the topographic map surveying and mapping results are formed after sorting.

[0032] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. A large-scale topographic mapping method based on oblique photography and airborne LiDAR, characterized in that: include: S1. Data collection: Oblique photography and airborne LiDAR data acquisition are performed simultaneously on the same photography platform; S2. 3D modeling: Divide the oblique photography images into image groups; use the regional network joint adjustment without ground control to deal with the geometric deformation and occlusion between the images; import the image control points into the engineering block and measure the ground image control points on the image; perform aerial triangulation based on the bundle method regional network adjustment to obtain the exterior orientation elements of the oblique image data at the time of aerial photography, and obtain the coordinates of the encrypted points in the image in the object space coordinate system; based on the results of aerial triangulation, reconstruct the three-dimensional model based on the oblique image data; S3. Collection of landforms and features: Based on the reconstructed 3D model, collect the elevation of objects, landforms, and elevation points; S4, LiDAR point cloud classification and contour data production: Obtain DEM data based on LiDAR point cloud data, and derivate contour data based on the acquired DEM data; S5. Data fusion: The layers contained in the objects and landforms collected by S3 and the contour data obtained by S4 are merged into one data to obtain topographic map data; S6. Field survey and data editing: Through field survey and mapping, field data is obtained, topographic map data is verified and modified, and after being sorted out, topographic mapping results are formed.

2. The large-scale topographic mapping method based on oblique photography and airborne LiDAR according to claim 1, characterized in that: In S2, dividing the oblique photography images into image groups includes: dividing the images taken by the same camera and having the same internal orientation into one image group.

3. The large-scale topographic mapping method based on oblique photography and airborne LiDAR according to claim 2, characterized in that: In S2, the image control points are imported into the engineering block, and in the step of measuring the ground image control points on the image, the thorn points are distributed on the photos of multiple flight strips.

4. The large-scale topographic mapping method based on oblique photography and airborne LiDAR according to claim 3, characterized in that: In S2, the aerial triangulation based on bundle block adjustment includes the following steps: Feature point extraction: extract the characteristic points in each image and mark and name them; Feature point matching: associate points with the same name in different images; Bundle method block adjustment; The adjustment equation is as follows: Where X1 is the correction number of the exterior orientation element and the encrypted point coordinates; P1 is the weight of the image point observation value; X2 is the correction number of the control point coordinates; P2 is the weight of the control point coordinate observation value; X3 is the correction number of the exterior orientation element; P3 is the weight of the exterior orientation element; X4 is the self-calibration parameter; P4 is the weight of the self-calibration parameter; A1, A2, A3, A4 are the coefficient matrices of the error equation; E1, E2, E3, E4 are the unit matrices; L1, L2, L3, L4 are the image point observation value vectors; V1, V2, V3, V4 are the error result matrices.

5. The large-scale topographic mapping method based on oblique photography and airborne LiDAR according to claim 3, characterized in that: In S2, when the same-name points cannot be accurately matched or the mirror reflection interferes with the same-name points, the 3D production software Reconstruction Master is used to automatically generate a real-scene 3D model; when there are deviations in the water surface material part and the small ground object part, the DPmodeler system is used to modify the local geometric model errors of the automatically generated 3D model.

6. The large-scale topographic mapping method based on oblique photography and airborne LiDAR according to claim 5, characterized in that: In S3, based on the reconstructed 3D model, the steps of collecting the elevations of objects, landforms, and elevation points are as follows: The acquisition of planar and linear spatial features is carried out directly on the 3D model. If the accuracy of the 3D model cannot meet the requirements, it can be collected in combination with oblique images. For the collection of point-shaped spatial objects, the primary and secondary oblique images can be retrieved to determine the point position using the principle of forward intersection; The elevation of the elevation point is the spatial three-dimensional data obtained by pixel-by-pixel matching based on the oblique photogrammetry software. The elevation points are collected in open areas without trees or tall buildings.

7. The large-scale topographic mapping method based on oblique photography and airborne LiDAR according to any one of claims 1 to 6, characterized in that: In S4, in the step of obtaining DEM data based on LiDAR point cloud data: The airborne LiDAR point cloud data is solved using the differential GNSS data and IMU data output by the inertial navigation system to obtain real-time position data; Use LiDAR 360 software to pre-process the LiDAR point cloud and filter out points that are obviously below the ground and points that are obviously above the ground; Create a new project in SCOP++ software, add data layer in Add model overlay window, input layer name, obtain ground points, interpolate to generate DEM data, and perform point cloud classification; Check and set the DSM grid size, and select Robust filtering and LiDAR Defalt Strong template strategies; In the selected LiDAR Defalt Strong template strategy, set the cell mesh size in Thinout step3, Thinout step7, and Thinout step11 to perform thinning; Perform filtering. After filtering, the point cloud is layered into LowPoint, Building, HighVegetationg, MediumVegetationg, LowVegetation, GroundSynthetic, and Ground layers, and the ground point Ground layer is retained; Modify the sampling grid size and bridge node distance in FillvoidAreas Step 13 to fill the DEM data grid.

8. The large-scale topographic mapping method based on oblique photography and airborne LiDAR according to claim 7, characterized in that: In S4, in the step of derivation from the acquired DEM data into contour data: Use ArcGis software to invert contour data: open ArcToolBox 3D Analyst Tools RasterSurfaceContour, set parameters in the pop-up dialog box, output file type as *.shp, and generate preliminary contour data; Contour line smoothing: Open ArcToolbox Cartography Tools Generalization SmoothLine, set parameters according to the terrain, and smooth the contour lines; Add fields: Add fields GB and ELEV, where the data type of GB is Text (9) and ELEV is Double; enter the calculation formula GB code in the GB column, run the field operator in the ELEV column, and assign its value to the ELEV attribute item; Among them, for the inversely derived contour data, if there is distortion of contour lines after filtering in areas with dense vegetation, if the filtering is not completely based on ground points, or if the relationship between ridges and contour lines is unreasonable, modifications will be made in combination with the three-dimensional model.

9. The large-scale topographic mapping method based on oblique photography and airborne LiDAR according to claim 1, characterized in that: In S6, in the step of obtaining field data through field survey and mapping: For linear features blocked by trees, small independent features, and features that are difficult to interpret in-house, information is obtained through mapping in the field; Place names, pipeline directions, and pipeline names are obtained through field mapping.

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