A topographic mapping method based on oblique photography technology

Abstract

The present invention relates to the technical field of topographic surveying and mapping, and specifically relates to a topographic surveying and mapping method based on oblique photography technology, which includes the following steps: reading aerial images and flight line information, where the aerial images include aerial images captured by cameras at multiple angles; establishing a landmark model based on the aerial images and dividing the landmark points of the landmark model; obtaining the position coordinates of the camera corresponding to each aerial image from the flight line information; reading the aerial images captured by cameras at multiple angles where all the landmark points appear to obtain the three-dimensional coordinates of the landmark points; obtaining the three-dimensional coordinate information of the landmark model based on the three-dimensional coordinates of the landmark points; establishing a terrain model from the established landmark model and the three-dimensional coordinate information of the landmark model as the result of topographic surveying and mapping. The beneficial technical effects of the present invention include: based on oblique photography, images of a landmark model on the ground can be obtained at multiple angles, and the three-dimensional coordinate information of the landmark model can be obtained, thereby realizing topographic surveying and mapping, and a terrain model is formed by the established landmark model.

Description

Technical Field

[0001] The present invention relates to the technical field of terrain surveying and mapping, and in particular to a terrain surveying and mapping method based on oblique photography technology. Background Art

[0002] Topographic survey refers to the work of mapping topographic maps. That is, the projection position and elevation of the objects and terrain on the horizontal plane in a certain area are measured, and then they are reduced to a certain scale and drawn into a topographic map with symbols and annotations. Topographic survey mainly adopts aerial photogrammetry, including control measurement and detailed measurement. According to the different instruments used, detailed measurement is mainly divided into planar instrument mapping method, small planar instrument and theodolite combined mapping method, theodolite mapping method, etc. The main purpose of topographic survey is to ensure the good currentness of topographic maps and the requirements for updating basic geographic information data, so as to meet the needs of urban planning, construction, and management, and better provide surveying and mapping services and guarantees for all sectors of society.

[0003] Oblique photography is a high-tech technology developed in the field of international photogrammetry in the past decade. This technology acquires rich high-resolution textures of the top and side views of buildings by synchronously collecting images from a vertical and four oblique directions, a total of five different perspectives. It can not only truly reflect the situation of the ground objects, but also obtain the texture information of the objects with high precision. However, most of these images only have information features of the top of the ground objects, lack detailed contours and elevation information on the sides of the ground objects, which is not conducive to all-round model reconstruction and scene perception. Therefore, it is necessary to study terrain mapping technology based on oblique photography and related modeling technology.

[0004] The prior art discloses an oblique photography topographic mapping device, including an aircraft, a housing, an oblique photography module for collecting images, and a driving mechanism. The housing is provided with a containing cavity and an opening connected to the containing cavity, and the housing is arranged at the bottom of the aircraft; the housing is provided with a door body that can open or close the opening. The driving mechanism is connected to the housing or the aircraft, and the driving mechanism is used to drive the oblique photography module to extend out of the opening when the door body is opened, and to close the opening when the oblique photography module is retracted into the containing cavity. The extension or retraction of the oblique photography module is linked to the movement of the door body, which is easy to control, shortens the adjustment time, and improves efficiency. Although its technical solution realizes the acquisition of terrain images based on oblique photography, it cannot solve the problem of the current lack of terrain mapping models based on terrain images collected by oblique photography. Summary of the invention

[0005] The technical problem to be solved by the present invention is that there is currently a lack of a solution for establishing a terrain model based on oblique photography images. A terrain surveying and mapping method based on oblique photography technology is proposed, which can establish a terrain model based on the collected oblique photography images.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions: A topographic surveying method based on oblique photography technology, comprising the following steps:

[0007] Read aerial images and route information, where the aerial images include aerial images captured by multiple-angle cameras;

[0008] Establish a landmark model based on the aerial images and divide the landmark points of the landmark model;

[0009] Obtain the position coordinates of the camera corresponding to each aerial image from the route information;

[0010] Read the aerial images captured by multiple-angle cameras where all the landmark points appear to obtain the three-dimensional coordinates of the landmark points;

[0011] Obtain the three-dimensional coordinate information of the landmark model based on the three-dimensional coordinates of the landmark points;

[0012] Establish a topographic model from the established landmark model and the three-dimensional coordinate information of the landmark model as the result of topographic surveying.

[0013] Preferably, the route information includes multiple navigation points, the position coordinates of the navigation points, the timestamps of arriving at the navigation points, and the flight speeds at the navigation points. The multiple navigation points are connected in sequence to form a route.

[0014] Preferably, the aerial images are associated with shooting timestamps. The method for obtaining the position coordinates of the camera includes:

[0015] Find the two navigation points with the closest shooting timestamps of the aerial images to obtain the position coordinates of the two navigation points;

[0016] Use the position coordinates of the two navigation points and the timestamps to establish a function of the position coordinates of the navigation points with respect to the timestamps;

[0017] Substitute the shooting timestamp into the function to obtain the position coordinates of the camera.

[0018] Preferably, the method for establishing a landmark model based on the aerial images includes:

[0019] Establish landmark model elements and area templates;

[0020] Use the area templates to identify the areas in the aerial images;

[0021] Associate the areas with the area types of the corresponding area templates;

[0022] Identify the boundaries in the areas;

[0023] Use the preset landmark model elements to match with the boundaries and establish a landmark model based on the successfully matched landmark model elements.

[0024] Preferably, the area templates include a road area template, a building area template, a square area template, and a greening area template. The road area template includes a road color range and a road surface feature matching set. The road surface feature set includes a crosswalk matching template, a traffic light matching template, and a road shape matching template. Extract the color areas in the aerial image that conform to the road color range, obtain the envelope area of the color areas, and attempt to use the road surface feature matching set to match the local areas of the envelope area within the envelope area. If there is a local area that matches any of the matching templates in the road surface feature matching set, it is determined that the envelope area is a road area;

[0025] The square area template includes a square shape matching template. Extract the color blocks in the aerial image, remove the color blocks with a pixel area smaller than a preset threshold, and obtain the envelope line of the remaining color blocks. If the envelope line can match the square shape matching template after rotation and perspective transformation, it is determined that the area enclosed by the envelope line is a square area. The greening area template records the greening area color range. Extract the color areas in the aerial image that conform to the greening area color range, remove the areas with a pixel area smaller than a preset threshold, and the remaining areas are used as the greening area. The building area template includes several building contour matching templates. Extract the color block edges in the aerial image. After rotating, scaling, and perspective transforming the building contour matching templates, match them with the color block edges. If the matching is successful, it is determined that the color block edge is a building edge, and use a polygon area composed of broken lines to enclose all the building edges. The polygon area is regarded as the building area.

[0026] Preferably, the method for establishing the object model element includes:

[0027] Establish a road model element. The road model element includes a road cross-sectional shape and an extension curve. After the extension curve matches the center line of the road area in the aerial image, the road cross-section extends along the extension curve to form a road model;

[0028] Establish a columnar building model element. The columnar building model element includes several preset bottom shapes and column heights. The bottom shape matches the bottom shape of the building in the aerial image, and the column height matches the building height in the aerial image. The bottom shape extends along the vertical line to reach the column height to form a columnar building model;

[0029] Establish a special-shaped building model element. The special-shaped building model element includes several envelope curves. The envelope curves are in the vertical plane. After several envelope curves match the vertical cross-sectional shape of the special-shaped building, a special-shaped building model is formed;

[0030] Establish a square model element. The square model element includes a polygon contour. After the polygon contour matches the square area in the aerial image, it is stretched vertically by a preset thickness to form a square model.

[0031] Preferably, the method for dividing the object points of the object model includes:

[0032] Mark the object boundary of the object model element, and set a number of preset object points on the object boundary;

[0033] According to the orientation during boundary matching in the object model element area, obtain the object boundary and preset object points in the visible state, and use the preset object points in the visible state as the selected object points on the object model;

[0034] Obtain the corresponding boundary in the aerial image of the object boundary corresponding to the object point;

[0035] Select aerial images at two angles on the flight path, so that the selected aerial images at two angles satisfy that the corresponding boundaries of the object boundary can be found in both aerial images at two angles;

[0036] The aerial images corresponding to the two angles are used as the two selected aerial images.

[0037] Preferably, the method for marking the object boundary of the object model element includes:

[0038] Mark all vertices of the object model element, and the connection lines between the vertices are used as the object boundary.

[0039] Preferably, the method for obtaining the three-dimensional coordinate information of the object model based on the three-dimensional coordinates of the object point includes:

[0040] Substitute the three-dimensional coordinates of the object point into the rotated and scaled object model to obtain the endpoint coordinate information of the object boundary of the object model, and the endpoint coordinate information of all object boundaries constitutes the three-dimensional coordinate information of the object model.

[0041] Preferably, the method for obtaining the three-dimensional coordinates of the object point includes:

[0042] Establish the visual field area of each camera on the sea level, denoted as the reference visual field area, and obtain the relative coordinates of each point in the reference visual field area relative to the camera;

[0043] Obtain the pixel position of the object point in the aerial image, and then the coordinates of the mapping point on the corresponding reference visual field area;

[0044] The object point is on the connection line between the camera coordinate and the mapping point;

[0045] Two aerial images will obtain the coordinate information of the two connection lines where the object point is located, and the intersection coordinate of the two connection lines is the three-dimensional coordinate of the object point.

[0046] The beneficial technical effects of the present invention include: based on oblique photography, images of a target model on the ground can be obtained from multiple angles. By dividing the target points and identifying the three-dimensional coordinates of the target points, the three-dimensional coordinate information of the target model can be obtained, thereby realizing topographic surveying and mapping, and a topographic model is formed by the established target model; by using a regional template to identify regions in the aerial images and then establishing a target model according to the type of the region, the creation efficiency of the target model can be accelerated and the accuracy of the target model can be improved.

[0047] Other features and advantages of the present invention will be disclosed in detail in the following specific embodiments and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention will be further described below with reference to the accompanying drawings:

[0049] Figure 1 It is a schematic flowchart of the topographic surveying and mapping method according to an embodiment of the present invention.

[0050] Figure 2 It is a schematic flowchart of the method for obtaining the position coordinates of a camera according to an embodiment of the present invention.

[0051] Figure 3 It is a schematic flowchart of the method for establishing a target model according to an embodiment of the present invention.

[0052] Figure 4 It is a schematic flowchart of the method for establishing the meta-target model according to an embodiment of the present invention.

[0053] Figure 5 It is a schematic diagram of the road area matching according to an embodiment of the present invention.

[0054] Figure 6 It is a schematic diagram of the area matching according to an embodiment of the present invention.

[0055] Figure 7 It is a schematic diagram of the columnar building model according to an embodiment of the present invention.

[0056] Figure 8 It is a schematic flowchart of the method for dividing the target points of the target model according to an embodiment of the present invention.

[0057] Figure 9 It is a schematic flowchart of the method for obtaining the three-dimensional coordinates of the target points according to an embodiment of the present invention.

[0058] Figure 10 It is a schematic diagram of the reference vision area according to an embodiment of the present invention.

[0059] Figure 11 It is a schematic flowchart of the topographic surveying and mapping method according to an embodiment of the present invention.

[0060] Wherein: 10, road area; 11, road model; 20, aerial image; 30, greening area; 40, building area; 41, boundary; 50, cylindrical building model element; 51, deformed cylindrical building model element; 60, cylindrical building model; 70, camera; 80, reference visual field area; 81, mapping point. Detailed implementation manners

[0061] The technical solutions of the embodiments of the present invention will be explained and described below with reference to the accompanying drawings of the embodiments of the present invention. However, the following embodiments are only the preferred embodiments of the present invention, not all of them. Based on the embodiments in the implementation manners, other embodiments obtained by those skilled in the art without creative efforts all fall within the protection scope of the present invention.

[0062] In the following description, terms such as "inside", "outside", "above", "below", "left", "right", etc. indicating orientations or positional relationships are only for convenience of describing the embodiments and simplifying the description, rather than indicating or implying that the devices or elements referred to must have specific orientations, be constructed and operated in specific orientations, and therefore cannot be construed as limitations of the present invention.

[0063] Before introducing the technical solutions of this embodiment, the relevant application background of this embodiment will be introduced.

[0064] The main purpose of topographic surveying work is to ensure the good currency of topographic maps and the requirements for updating basic geographic information data, so as to meet the needs of urban planning, construction, and management, and better provide surveying and mapping services and guarantees for all sectors of society. With the development of big data technology, applications based on big data have been taken seriously in all walks of life. For example, in the fields of power grid planning, road construction planning, fire fighting dispatch, etc. And a large number of big data applications among them need to obtain topographic data within the region as a support. However, the current topographic surveying and mapping technologies are not only inefficient, but also difficult to obtain topographic models, which limits the development and application of these technologies.

[0065] Oblique photography technology is a high-tech developed in the international photogrammetry field in the past ten years. This technology synchronously collects images from one vertical and four oblique directions, a total of five different perspectives, and obtains rich high-resolution textures of the top and side views of buildings. It can not only truly reflect the situation of ground objects and accurately obtain object-side texture information. However, most of these images only have the information characteristics of the top of the ground objects, lacking detailed contour and elevation information on the sides of the ground objects, which is not conducive to all-round model reconstruction and scene perception. Therefore, it is necessary to study topographic surveying and mapping technologies based on oblique photography and related modeling technologies.

[0066] For this reason, this embodiment provides a topographic surveying and mapping method based on oblique photography technology. Please refer to the attached Figure 1 , including the following steps:

[0067] Step A01) Read the aerial images 20 and the route information. The aerial images 20 include the aerial images 20 captured by multiple-angle cameras 70;

[0068] Step A02) Establish a landmark model based on the aerial images 20 and divide the landmark points of the landmark model;

[0069] Step A03) Obtain the position coordinates of the camera 70 corresponding to each aerial image 20 from the route information;

[0070] Step A04) Read the aerial images 20 captured by multiple-angle cameras 70 where all the landmark points appear to obtain the three-dimensional coordinates of the landmark points;

[0071] Step A05) Obtain the three-dimensional coordinate information of the landmark model based on the three-dimensional coordinates of the landmark points;

[0072] Step A06) Establish a terrain model from the established landmark model and the three-dimensional coordinate information of the landmark model as the terrain mapping result.

[0073] The route information includes multiple navigation points, the position coordinates of the navigation points, the timestamps of arriving at the navigation points, and the flight speeds at the navigation points. The multiple navigation points are connected in sequence to form a route. The route information is obtained by the aircraft recording during flight. After obtaining the aerial images 20, a landmark model is established based on the aerial images 20, and the shape and orientation of the landmark model are obtained from the landmark points of the landmark model. After all the landmark models are established, the un-covered surface area by the landmark models is supplemented with a preset surface model to complete the modeling of all terrains. Select any point on the blank surface and calculate the three-dimensional coordinates to obtain the altitude of the ground. The surface model has a preset thickness. After adapting the upper surface of the surface model to the altitude, a surface model matching the aerial images 20 can be obtained.

[0074] The aerial images 20 are associated with the shooting timestamps. Please refer to the appendix Figure 2 , and the method for obtaining the position coordinates of the camera 70 includes:

[0075] Step B01) Find the two navigation points whose shooting timestamps of the aerial images 20 are the closest and obtain the position coordinates of the two navigation points;

[0076] Step B02) Use the position coordinates of the two navigation points and the timestamps to establish a function of the position coordinates of the navigation points against the timestamps;

[0077] Step B03) Substitute the shooting timestamp into the function to obtain the position coordinates of the camera 70. By finding the two navigation points whose shooting timestamps of the aerial images 20 are the closest, and according to the timestamp of the aerial images 20, the corresponding position coordinates of the aerial images 20 are calculated. This position coordinate is the position coordinate of the aircraft positioning point. The aircraft positioning point is usually the positioning point of the GPS module.

[0078] Please refer to the appendix Figure 3 , the method for establishing a landmark model based on the aerial image 20 includes:

[0079] Step C01) Establish landmark model elements and area templates;

[0080] Step C02) Use the area template to identify the areas in the aerial image 20;

[0081] Step C03) Associate the area with the area type of the corresponding area template;

[0082] Step C04) Identify the boundary 41 in the area;

[0083] Step C05) Use the preset landmark model elements to match with the boundary 41, and establish a landmark model according to the successfully matched landmark model elements. By establishing an area template, after using the area template to match the areas in the aerial image 20, a landmark model is established within the area, which can improve the efficiency and accuracy of establishing the landmark model.

[0084] The area templates used in this embodiment include a road area 10 template, a building area template, a square area template, and a greening area 30 template. The road area 10 template includes a road color range and a pavement feature matching set. The pavement feature set includes a crosswalk matching template, a traffic light matching template, and a road shape matching template. Extract the color areas in the aerial image 20 that meet the road color range, obtain the envelope area of the color areas, and try to use the pavement feature matching set to match the local areas in the envelope area. If there is a local area that matches any of the matching templates in the pavement feature matching set, it is determined that the envelope area is the road area 10; the square area template includes a square shape matching template. Extract the color blocks in the aerial image 20, remove the color blocks with a pixel area smaller than a preset threshold, obtain the envelope line of the remaining color blocks. If the envelope line can match the square shape matching template after rotation and perspective transformation, it is determined that the area enclosed by the envelope line is the square area. The greening area 30 template records the greening area 30 color range. Extract the color areas in the aerial image 20 that meet the greening area 30 color range, remove the areas with a pixel area smaller than a preset threshold, and the remaining area is used as the greening area 30. The building area template includes several building contour matching templates. Extract the color block boundaries in the aerial image 20, and after rotating, scaling, and perspective transforming the building contour matching templates, match them with the color block boundaries. If the match is successful, it is determined that the color block boundary is the building boundary, and a polygon area composed of broken lines is used to enclose all the building boundaries, and the polygon area is regarded as the building area.

[0085] Please refer to the appendix Figure 4 , the method for establishing landmark model elements includes:

[0086] Step D01) Establish an 11 - element road model. The 11 - element road model includes the cross - sectional shape of the road and the extension curve. After the extension curve is matched with the center line of the road area 10 in the aerial image 20, the road cross - section extends along the extension curve to form the road model 11;

[0087] Step D02) Establish a cylindrical building model element 50. The cylindrical building model element 50 includes several preset bottom shapes and column heights. The bottom shape is matched with the bottom shape of the building in the aerial image 20, and the column height is matched with the building height in the aerial image 20. The bottom shape extends along the vertical line to reach the column height, constituting the cylindrical building model 60;

[0088] Step D03) Establish a special - shaped building model element. The special - shaped building model element includes several envelope curves. The envelope curves are on the vertical plane. After several envelope curves match the vertical cross - sectional shape of the special - shaped building, they constitute the special - shaped building model;

[0089] Step D04) Establish a square model element. The square model element includes a polygonal contour. After the polygonal contour is matched with the square area in the aerial image 20, it is stretched vertically by a preset thickness to constitute the square model. For different areas, corresponding object model elements are established.

[0090] Please refer to Appendix Figure 5 , in the aerial image 20, extract the preset road color range, the shape of the road can be obtained, and then stretch it along the preset extension thickness, and the three - dimensional road model 11 can be obtained. The preset extension thickness is a constant value, which is selected according to the local road construction specifications or the average value of the road thickness in the area.

[0091] Please refer to Appendix Figure 6 , which is a schematic diagram of the area division result. By dividing the aerial image 20 into multiple areas, the types of ground appendages in each area become fewer. Thus, the object model can be established quickly and the accuracy of establishing the object model can be improved.

[0092] Please refer to Appendix Figure 7 , which is the process of matching the object model element with the aerial image 20. Extract the boundary 41 of the color block from the aerial image 20. The extraction of the boundary 41 of the color block belongs to the prior art in this field and will not be elaborated here. After obtaining the boundary 41, select the corresponding object model element, Figure 7 select the cylindrical building model element 50 in. Modify the bottom shape of the cylindrical building model element 50 to match the boundary 41, and then scale and rotate the cylindrical building model element 50 to obtain the deformed cylindrical building model element 51. Then align the deformed cylindrical building model element 51 with the position of the boundary 41 in the aerial image 20, and the cylindrical building model 60 is obtained.

[0093] Please refer to Appendix Figure 8, the method of dividing the object points of the object model includes:

[0094] Step E01) marking the object boundary 41 of the object model element, and setting a number of preset object points on the object boundary 41;

[0095] Step E02) obtaining the object boundary 41 and the preset object point in a visible state according to the orientation of the boundary 41 in the object model element region when matched, and using the preset object point in the visible state as the selected object point on the object model;

[0096] Step E03) obtaining the boundary 41 corresponding to the object boundary 41 of the object point in the aerial image 20;

[0097] Step E04) selecting two aerial images 20 at two angles on the route, so that the aerial images 20 at two angles are selected to satisfy the requirement that the boundary 41 corresponding to the object boundary 41 can be found in the aerial images 20 at the two angles;

[0098] Step E05 ) The aerial images 20 corresponding to the two angles are selected as two aerial images 20 .

[0099] By taking oblique photos at the same position, images of at least two perspectives of the same object can be obtained. The three-dimensional coordinates of the visible points on the object can be calculated through the images of these two perspectives. By selecting aerial images 20 at two angles on the route, so that the aerial images 20 at two angles can find the boundary 41 corresponding to the object boundary 41, the aerial images 20 that can calculate the three-dimensional coordinates of the visible points can be found.

[0100] The method of marking the object boundary 41 of the object model element includes: marking all vertices of the object model element, and the lines between the vertices are used as the boundary 41 of the object model.

[0101] The method of obtaining the three-dimensional coordinate information of the object model according to the three-dimensional coordinates of the object point includes:

[0102] Substitute the three-dimensional coordinates of the object point into the rotated and scaled object model to obtain the endpoint coordinate information of the object boundary 41 of the object model. The endpoint coordinate information of all object boundaries 41 constitutes the three-dimensional coordinate information of the object model.

[0103] Please see attached Figure 9 , the method of obtaining the three-dimensional coordinates of the object point includes:

[0104] Step F01) establishing the field of view of each camera 70 at sea level, recorded as reference field of view 80, and obtaining the relative coordinates of each point in the reference field of view 80 relative to the camera 70;

[0105] Step F02) Obtain the pixel position of the object point in the aerial image 20, and then the coordinates of the mapping point 81 on the corresponding reference vision area 80;

[0106] Step F03) The object point is on the line connecting the coordinates of the camera 70 and the mapping point 81;

[0107] Step F04) Two aerial images 20 will obtain the coordinate information of the two lines where the object point is located, and the intersection coordinates of the two lines are the three-dimensional coordinates of the object point.

[0108] Please refer to the attached Figure 10 , which is a schematic diagram of the aerial image 20 taken in this embodiment. When the camera 70 takes a straight-down shot at the altitude H, the position of the vision area on the horizontal plane is only related to the position of the camera 70. By determining the three-dimensional coordinates of the camera 70 and combining the viewing angle range of the camera 70, the three-dimensional coordinate information of the reference vision area 80 can be determined. The camera 70 takes a ground image as the aerial image 20, and the aerial image 20 has a certain altitude. For any pixel point on the aerial image 20, the extension line of the connection with the camera 70 intersects with the reference vision area 80, and the intersection point is denoted as the mapping point 81. The coordinates of the mapping point 81 can be uniquely determined by the pixel position of the corresponding pixel point in the aerial image 20. From the mapping point 81 and the position where the camera 70 is located, the analytical formula of a straight line can be established in the geodetic coordinate system. The object point is on this straight line.

[0109] Please refer to the attached Figure 11 , then read the aerial image 20 at another angle, and the analytical formula of another straight line can also be obtained, and the object point is also on this straight line. Solve the intersection coordinates of the two straight lines to obtain the three-dimensional coordinates of the object point. Select several preset object points on the object model. After obtaining the three-dimensional coordinates of the object points, the three-dimensional coordinate information of the object model can be obtained, and the object model can be completely established, and then the topographic surveying can be completed.

[0110] Specifically, the method for establishing the topographic surveying result according to the boundary 41 coordinates includes: merging the object models with a volume coincidence degree exceeding the preset threshold according to the coordinate information of the object model; all the merged object models form a terrain model, and the terrain model is used as the topographic surveying result.

[0111] The beneficial technical effects of this embodiment include: based on oblique photography, images of the object model on the ground at multiple angles can be obtained. By dividing the object points and identifying the three-dimensional coordinates of the object points, the three-dimensional coordinate information of the object model can be obtained, so as to realize topographic surveying, and the terrain model is formed by the established object model; by using the area template to identify the area in the aerial image 20 and then establishing the object model according to the type of the area, the creation efficiency of the object model can be accelerated and the accuracy of the object model can be improved.

[0112] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the content described in the drawings and the above specific implementation manner. Any modification that does not deviate from the functional and structural principles of the present invention will be included in the scope of the claims.

Claims

1. A topographic surveying method based on oblique photography technology, characterized in that it includes the following steps: Read aerial images and flight path information, where the aerial images include aerial images captured by cameras at multiple angles; Establish a landmark model based on the aerial images and divide the landmark points of the landmark model; Obtain the position coordinates of the camera corresponding to each aerial image from the flight path information; Read the aerial images captured by cameras at multiple angles where the landmark points all appear to obtain the three-dimensional coordinates of the landmark points; Obtain the three-dimensional coordinate information of the landmark model based on the three-dimensional coordinates of the landmark points; Establish a topographic model from the established landmark model and the three-dimensional coordinate information of the landmark model as the result of topographic surveying; The method for establishing a landmark model based on the aerial images includes: Establish landmark model elements and region templates; Use the region templates to identify regions in the aerial images; Associate the regions with the region types of the corresponding region templates; Identify the boundaries in the regions; Use the preset landmark model elements to match the boundaries, and establish a landmark model according to the successfully matched landmark model elements; The method for dividing the landmark points of the landmark model includes: Mark the landmark boundaries of the landmark model elements and set a number of preset landmark points on the landmark boundaries; According to the azimuth during boundary matching in the region of the landmark model element, obtain the landmark boundaries and preset landmark points in the visible state, and use the preset landmark points in the visible state as the selected landmark points on the landmark model; Obtain the boundaries corresponding to the landmark boundaries of the landmark points in the aerial images; Select aerial images at two angles on the flight path, so that the selected aerial images at two angles satisfy that the boundaries corresponding to the landmark boundaries can be found in both aerial images at two angles; The aerial images corresponding to the two angles are used as the two selected aerial images.

2. The topographic surveying method based on oblique photography technology according to claim 1, characterized in that the flight path information includes multiple navigation points, the position coordinates of the navigation points, the timestamps for reaching the navigation points, and the flight speeds at the navigation points, and the multiple navigation points are connected in sequence to form a flight path.

3. The topographic surveying method based on oblique photography technology according to claim 2, characterized in that the aerial images are associated with shooting timestamps, and the method for obtaining the position coordinates of the camera includes: Find the two navigation points with the closest shooting timestamps of the aerial images to obtain the position coordinates of the two navigation points; Use the position coordinates of the two navigation points and the timestamps to establish a function of the position coordinates of the navigation points with respect to the timestamps; Substitute the shooting timestamp into the function to obtain the position coordinates of the camera.

4. The topographic surveying method based on oblique photography technology according to claim 1, characterized in that The area templates include a road area template, a building area template, a square area template, and a greening area template. The road area template includes a road color range and a road surface feature matching set. The road surface feature set includes a crosswalk matching template, a traffic light matching template, and a road shape matching template. Color areas that meet the road color range in the aerial image are extracted, and the envelope area of the color areas is obtained. In the envelope area, the local areas of the envelope area are tried to be matched with the road surface feature matching set. If there is a local area that matches any of the matching templates in the road surface feature matching set, it is determined that the envelope area is a road area; The square area template includes a square shape matching template. Color blocks in the aerial image are extracted, and color blocks with a pixel area smaller than a preset threshold are removed to obtain the envelope line of the remaining color blocks. If the envelope line can be matched with the square shape matching template after rotation and perspective transformation, it is determined that the area enclosed by the envelope line is a square area. The greening area template records the greening area color range. Color areas that meet the greening area color range in the aerial image are extracted, and areas with a pixel area smaller than a preset threshold are removed. The remaining areas are used as the greening area. The building area template includes several building contour matching templates. The color block edges in the aerial image are extracted. After the building contour matching templates are rotated, scaled, and perspective-transformed, they are matched with the color block edges. If the matching is successful, it is determined that the color block edges are building edges. A polygon area formed by broken lines is used to enclose all the building edges, and the polygon area is regarded as the building area.

5. The topographic surveying method based on the oblique photography technology according to claim 4, characterized in that, The method for establishing the object model element includes: Establishing a road model element, where the road model element includes a road shape and an extension thickness. After the road shape is matched with the center line of the road area in the aerial image, the road shape extends along the extension thickness to form a road model; Establishing a columnar building model element, where the columnar building model element includes several preset bottom surface shapes and a column height. The bottom surface shape is matched with the bottom surface shape of the building in the aerial image, and the column height is matched with the building height in the aerial image. The bottom surface shape extends along the vertical line to reach the column height to form a columnar building model; Establishing a special-shaped building model element, where the special-shaped building model element includes several envelope curves. The envelope curves are in the vertical plane. After several of the envelope curves are matched with the vertical cross-section shape of the special-shaped building, a special-shaped building model is formed; Establishing a square model element, where the square model element includes a polygon contour. After the polygon contour is matched with the square area in the aerial image, it is stretched vertically by a preset thickness to form a square model.

6. The topographic surveying method based on the oblique photography technology according to claim 1, characterized in that, The method for marking the object boundaries of the object model element includes: Marking all the vertices of the object model element, and the connection lines between the vertices are used as the boundaries of the object model.

7. The topographic surveying method based on the oblique photography technology according to claim 6, characterized in that, The method of obtaining the three-dimensional coordinate information of the object model according to the three-dimensional coordinates of the object point includes: Substitute the three-dimensional coordinates of the object point into the rotated and scaled object model to obtain the endpoint coordinate information of the object boundary of the object model. The endpoint coordinate information of all object boundaries constitutes the three-dimensional coordinate information of the object model.

8. A terrain surveying and mapping method based on oblique photography technology according to any one of claims 1 to 3, characterized in that: The method of obtaining the three-dimensional coordinates of the object point includes: Establish the field of view of each camera at sea level, record it as the reference field of view, and obtain the relative coordinates of each point in the reference field of view relative to the camera; Obtain the pixel position of the object point in the aerial image, and then the coordinates of the corresponding mapping point on the reference field of view; The object point is on the line connecting the camera coordinates and the mapping point; The two aerial images will obtain the coordinate information of the two connecting lines where the object points are located, and the coordinates of the intersection of the two connecting lines are the three-dimensional coordinates of the object points.

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