A drone shooting and reconstruction method and device for fine modeling of building facades

Abstract

The present invention discloses a drone shooting and reconstruction method and device for fine modeling of building facades, the method comprising: step S1, using a camera carried by a drone to shoot a building image vertically downward from the air, obtaining the plane and elevation information of the building after photogrammetric processing, selecting the outer contour range of the building, and constructing a rough three-dimensional framework model of the building in combination with the elevation information; step S2, extracting the floor plan of the building according to the rough model of the building, establishing the outer contour line of the building by the outer expansion boundary of the floor plan, generating a horizontal or vertical drone flight path of the building facade according to the outer contour line of the building, and obtaining the facade shooting image collected according to the drone flight path; step S3, fusing the vertically shot image data and the image data shot on the building facade for aerial triangulation, and constructing a three-dimensional model with a complete top and facade of the building.

Description

Technical Field

[0001] The present invention relates to the technical field of unmanned aerial vehicle applications, and in particular to a method and device for unmanned aerial vehicle photography and reconstruction for fine modeling of building facades. Background Art

[0002] With the rapid development of science and technology in my country, the deep integration of informatization and urbanization, and the transformation of digital cities to smart city construction, various industries have a strong demand for real-life 3D data. With its intuitive and efficient advantages, real-life 3D technology has gradually become an important means of expressing urban geographic information data. The combination of 3D model data and 2D attribute data has gradually been applied in the process of smart city construction, making up for the three-dimensional needs of digital city smart planning. At the same time, real-life 3D models are widely used in smart cities, urban planning, traffic management, digital public security, emergency security, earthquake prevention and disaster reduction, land resources, and cultural relics protection.

[0003] The traditional method of building modeling generally uses modeling software such as 3dsMax, Google Sketchup, Solidworks, and CATIA, and estimates the outline and height information of the building for manual modeling based on CAD two-dimensional vector graphics, image data, or manually taken photos.

[0004] Models made by traditional methods have beautiful appearance, but low precision, and require a lot of manual participation in the production process, with a long production cycle, which is suitable for modeling relatively regular buildings. For reverse reconstruction of irregular facades of existing buildings, the size and shape must be obtained first, and then modeling is done using software, which is labor-intensive, inefficient, and has poor feasibility.

[0005] The 3D modeling technology of oblique photography by unmanned aerial vehicles is a high-tech technology developed in recent years in the field of international geographic information, integrating traditional aerial photography technology and digital ground acquisition technology. It overcomes the limitation that traditional aerial photography technology can only shoot from a vertical angle. By carrying one or more sensors on the same flight platform, it collects images from 1 vertical angle and 4 oblique angles, which more realistically reflects the actual situation of the ground objects, makes up for the shortcomings of orthophotos, and can also perform various measurements based on images. The emergence of oblique photogrammetry technology has driven the rapid development of 3D modeling technology and its applications. In order to meet the needs of efficient and accurate 3D geographic information of buildings required by the rapid development of smart cities. Using the oblique photography technology of unmanned aerial vehicles to shoot buildings from multiple angles and quickly establish a 3D real-life model of buildings has become one of the important ways to solve this problem.

[0006] At present, the use of drone oblique photography 3D modeling technology for building modeling mainly adopts multi-lens oblique photography 3D modeling. By taking advantage of drones and oblique photography technology, real-scene modeling of an area can be quickly and accurately performed. That is, by carrying multi-angle cameras on the same flying platform and collecting images from different angles such as vertical and oblique, more complete and accurate information about ground objects can be obtained. These oblique images can be processed by software to generate a 3D model.

[0007] However, the current technology still has the following shortcomings: oblique photography generally shoots buildings from an aerial perspective, and the top modeling effect is better. However, for the facades and bottoms of buildings, the ground images captured are incomplete due to obstacles near the ground during the data collection process, resulting in serious streaking, blurring, holes, and low precision on the facades along the streets and the eaves and corners of the real-life 3D models. As a result, the model can be viewed from a distance but not up close, and can be browsed but not queried. These problems directly affect and restrict the wider application of oblique 3D real-life models. Summary of the invention

[0008] In order to overcome the deficiencies of the above-mentioned prior art, one of the objects of the present invention is to provide a drone photography and reconstruction method and device for fine modeling of building facades, so as to achieve the purpose of fine modeling of building facades.

[0009] To achieve the above-mentioned purpose, the present invention proposes a drone photography and reconstruction method for fine modeling of building facades, comprising the following steps:

[0010] Step S1, using a camera carried by a drone to shoot an image of a building vertically downward from the air, obtaining the plane and elevation information of the building after photogrammetry processing, selecting the outer contour range of the building, and constructing a rough three-dimensional framework model of the building in combination with the elevation information;

[0011] Step S2, extracting the floor plan of the building according to the rough model of the building, establishing the outer boundary of the floor plan to obtain the outer contour of the building, generating the horizontal or vertical UAV flight path of the building facade according to the outer contour of the building, and obtaining the facade shooting image collected by navigating according to the UAV flight path;

[0012] Step S3, the vertically shot image data and the building facade image data are fused for aerial triangulation to construct a complete three-dimensional model of the top and facade of the building.

[0013] Preferably, step S1 further comprises:

[0014] Step S100, planning the route of the drone according to the plane range and height of the building and combining the parameters of the drone, and taking aerial photos when the drone is flying along the planned route;

[0015] Step S101, performing photogrammetry processing on the image data taken vertically by the drone to obtain the plane image and elevation information of the building and its surrounding environment;

[0016] Step S102, selecting the outer contour range of the building according to the planar image of the building and its surrounding environment, and constructing a rough three-dimensional framework model of the building in combination with the elevation information.

[0017] Preferably, during the shooting process, the drone uses the real-time RTK on board to record the spatial coordinate information of each image data when shooting images, and the rough three-dimensional framework model has the spatial coordinate information of each image data.

[0018] Preferably, in step S100, the plane range and height of the building to be modeled are obtained, and the route planning is performed based on the obtained plane range and height, combined with the focal length of the camera carried by the drone, the image resolution of the roof, the heading overlap of adjacent photos, the lateral overlap of adjacent routes, etc. When the drone navigates according to the planned route, the carried camera is used to perform aerial photography to obtain vertically shot image data.

[0019] Preferably, step S2 further comprises:

[0020] Step S2 further comprises:

[0021] Step S200, extracting the floor plan of the building according to the rough 3D framework model, and taking the floor plan of the building according to the camera shooting distance (H q ) to establish a building buffer zone, treat the corners as arcs, and determine the shooting distance and flight interval of the drone during flight according to the overlap requirements;

[0022] Step S201, generating a shooting route around the building facade according to the outer expansion boundary of the building plan, the shooting distance, the route interval, and the minimum safe flight altitude and the maximum flight altitude known from the rough three-dimensional framework model;

[0023] Step S202: after the shooting route is generated, set to shoot the vertical image at equal distance or equal time.

[0024] Preferably, the camera shooting distance (H q ), which is determined by the focal length, image resolution and pixel size of the camera carried by the UAV.

[0025] Preferably, in step S201, a horizontal shooting route is generated along the outer boundary of the building plan, and the camera angle is 0°, and / or a vertical shooting route is generated along the outer boundary of the building plan, and the camera angle is 0°.

[0026] Preferably, during the vertical shooting process, the camera shooting vertical angle is also adjusted to 30° to 60° for supplementary shooting.

[0027] Preferably, in step S202, when navigating to a right-angle turn area, three photos are taken for transition: a straight line turning into an arc, the middle of an arc, and an arc turning into a straight line.

[0028] To achieve the above-mentioned purpose, the present invention further provides a drone shooting and reconstruction device for fine modeling of building facades, comprising:

[0029] The initial model building unit is used to use the camera carried by the drone to shoot the building image vertically downward from the air, obtain the plane and elevation information of the building after photogrammetry processing, select the outer contour range of the building, and build a rough three-dimensional framework model of the building in combination with the elevation information;

[0030] A building facade route planning unit is used to extract a floor plan of the building according to a rough model of the building, establish an outer boundary of the building floor plan to obtain an outer contour line of the building, generate a horizontal or vertical drone flight path of the building facade according to the outer contour line of the building, and obtain a facade shooting image collected by navigating according to the drone flight path;

[0031] The fusion processing unit is used to fuse the vertically shot images and the image data shot on the building facade to perform aerial triangulation and construct a complete three-dimensional model of the top and facade of the building.

[0032] Compared with the prior art, the drone shooting and reconstruction method and device for fine modeling of building facades of the present invention first uses a camera carried by a drone to vertically shoot an image of a building from the air downward, obtains the plane and elevation information of the building after photogrammetric processing, selects the outer contour range of the building, and constructs a rough three-dimensional framework model of the building in combination with the elevation information, then extracts the floor plan of the building according to the rough model of the building, establishes the outer contour line of the building by the outer expansion boundary of the floor plan, generates a horizontal or vertical drone flight path of the building facade according to the outer contour line of the building, obtains the facade shooting image collected according to the drone flight path, and finally fuses the vertically shot image data and the image data shot on the building facade for aerial triangulation, constructs a three-dimensional model with a complete top and facade of the building, and achieves the purpose of fine modeling of the building facade. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flowchart of the steps of a drone photography and reconstruction method for fine building facade modeling according to the present invention;

[0034] Figure 2a and Figure 2bThis is a schematic diagram of vertical photography by a drone in a specific embodiment of the present invention;

[0035] Figure 3 It is a typical building plan in a specific embodiment of the present invention;

[0036] Figure 4 This is a typical building facade shooting route (top view) in a specific embodiment of the present invention;

[0037] Figure 5 This is a typical horizontal shooting route of a building facade in a specific embodiment of the present invention (side view, 0° angle);

[0038] Figure 6 This is a typical vertical shooting route of a building facade in a specific embodiment of the present invention (side view, 0° angle);

[0039] Figure 7 This is a typical vertical shooting route of a building facade in a specific embodiment of the present invention (side view, 45° angle);

[0040] Figure 8 This is a structural diagram of an unmanned aerial vehicle photographing and reconstruction device for fine modeling of building facades according to the present invention. DETAILED DESCRIPTION

[0041] The following describes the implementation of the present invention through specific examples and in conjunction with the accompanying drawings. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific examples, and the details in this specification can also be modified and changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0042] Figure 1 The following is a flowchart of the steps of a drone photography and reconstruction method for fine modeling of building facades according to the present invention. Figure 1 As shown, the present invention provides a drone shooting and reconstruction method for fine modeling of building facades, comprising the following steps:

[0043] Step S1, use the camera carried by the drone to shoot the image of the building vertically downward from the air, obtain the plane and elevation information of the building after photogrammetry processing, select the outer contour range of the building, and combine the elevation information (minimum safe elevation and maximum elevation) to construct a rough three-dimensional framework model of the building.

[0044] Specifically, step S1 further includes:

[0045] Step S100, planning the route of the drone according to the plane range and height of the building in combination with the drone parameters, and taking aerial photos when the drone is navigating along the planned route.

[0046] Specifically, the plane range and height of the building to be modeled are obtained, and the route is planned based on the obtained plane range and height, combined with the focal length of the drone's camera, the image resolution of the roof, the heading overlap of adjacent photos, the lateral overlap of adjacent routes, etc., and the route planning file is imported into the drone, so that the drone can navigate according to the planned route and take aerial photos, such as Figure 2a and Figure 2b As shown in the figure, since the route planning of UAV is already a mature technology, the specific method of route planning does not belong to the protection scope of the present invention and will not be described in detail here.

[0047] Step S101, performing photogrammetry processing on the image data taken vertically by the drone to obtain the plane and elevation information of the building.

[0048] In a specific embodiment of the present invention, photogrammetric data processing is performed on the image data taken vertically by the drone, and the plane and elevation information of the building and the surrounding environment can be obtained according to the processing results through photogrammetric processing software, such as Pix4d, Contextcapture, Photoscan and other software.

[0049] Step S102: According to the planar image of the building and its surroundings, the accurate outer contour range of the building is selected, and combined with the elevation information (minimum safe elevation and maximum elevation), a rough three-dimensional framework model of the building is constructed.

[0050] During the shooting process, the drone also uses the real-time RTK on board to record the GPS information (latitude and longitude coordinates, geodetic height) of each photo when taking images. Therefore, the rough three-dimensional framework model also has relatively accurate spatial coordinate information.

[0051] Step S2, extracting the floor plan of the building according to the rough three-dimensional framework model of the building, and establishing the outer boundary of the building floor plan to obtain the outer boundary line of the building, and generating the horizontal or vertical drone flight path of the building facade according to the outer boundary line of the building, and obtaining the facade photos collected by navigating according to the drone flight path.

[0052] Specifically, step S2 further includes:

[0053] Step S200: extract the outer contour line (or plan view) of the building according to the rough 3D framework model, and use the outer contour line of the building to obtain the outer contour line of the building according to the camera shooting distance H. q A building buffer zone is established by expanding the outside of the building, and the corners are treated as arcs. The shooting distance and flight path interval of the drone are determined according to the overlap requirements.

[0054] In a specific embodiment of the present invention, the outer contour of the building is extracted according to the rough three-dimensional frame model of the building, which can generally be divided into a circle, a regular polygon, a rectangle and an irregular polygon, etc. Figure 3 As shown, the building buffer is the distance H from the outer contour line to the outer layer in the figure. q area.

[0055] In the present invention, the distance between the drone and the building facade, i.e., the camera shooting distance (H q ), which is determined by the focal length, image resolution, and pixel size of the camera. Specifically, the camera shooting distance (H q ) and the camera image resolution (GSD), focal length (f), and pixel size (p) are related as shown in (Equation 1):

[0056]

[0057] Assume that the camera's field of view is (fov x , fov y ), the photo covers the building facade area G i , when i is x, y, it represents the coverage range G in the horizontal and vertical directions respectively x , G y ,, the formula is as follows:

[0058]

[0059] Since the photos taken must meet certain overlap requirements, during the route planning process, the heading overlap is set to o. x , the lateral overlap is o y , corresponding to the heading overlap length O x , the lateral overlap length is O y The interval between two adjacent exposure points in the heading direction (horizontal direction) is Δs, and the height difference between adjacent routes in the lateral direction (vertical direction) is Δh. The calculation formula is:

[0060]

[0061]

[0062] That is, the shooting distance during the flight of the UAV can be determined according to Δs, and Δh can be used to determine the interval between two routes.

[0063] Step S201, generating a shooting route around the building facade according to the outer expansion boundary of the building plan, the shooting distance, the route interval, and the minimum safe flight altitude and the maximum flight altitude known from the rough three-dimensional framework model.

[0064] Case 1: Horizontal flight path along the building facade

[0065] Specifically, a horizontal shooting route is generated along the outer boundary of the building outline, such as Figure 4 During the shooting process, the camera angle was 0° because it was facing the facade.

[0066] Case 2: Longitudinal flight path of the building facade

[0067] Specifically, a longitudinal shooting route is generated along the outer boundary of the building plan, such as Figure 5 During the shooting process, the camera angle was 0 degrees because it was facing the facade.

[0068] For building facades with uneven surfaces, such as eaves and balconies, there may still be blind spots after the previous two shooting methods, and additional shooting is required. That is, during the vertical shooting process, adjust the camera's shooting angle of the facade to 30°~60° for additional shooting. Figure 6 shown.

[0069] Step S202, after the shooting route is generated, setting to shoot the vertical image at equal distance or equal time.

[0070] Specifically, when isochronous shooting is set, the flight speed v and the overlap distance (i.e., the course overlap length is 0) are set. x ) to calculate the shooting time interval Δt, that is: Δt = O x / v

[0071] When setting equal distance shooting, the overlap distance (i.e. the heading overlap length is 0) is used. x ) as the shooting distance interval Δd.

[0072] For the right-angle turning area, the success rate of subsequent aerial triangulation needs to be considered. Regardless of whether the photos are taken at equal times or at equal distances, the present invention needs to take three photos at the corner for transition, namely, the straight line turns to the arc, the middle of the arc, and the arc turns to the straight line. Figure 7 shown.

[0073] Step S3, the vertically shot images and the image data shot on the building facade are fused for aerial triangulation to construct a relatively complete three-dimensional model of the top and facade of the building.

[0074] Specifically, the vertically shot images and the image data of the building facades are imported into the oblique photography 3D modeling software, such as Contextcapture center, Smart3d, etc., and the camera parameters (focal length, etc.) of each group of photos are set; the image data are used for free network adjustment (i.e., feature point extraction and image matching), which mainly includes feature point extraction, image matching, etc., and the relative position relationship between the images is calculated; if there are photo control points, the control points are imported into the software and punctured on the photos; the photo control point constraint adjustment calculation is performed again to obtain the precise exterior orientation elements of each photo, that is, the aerial triangulation process is completed; the model is constructed, that is, dense matching is first performed to generate dense point cloud data, and then triangulation network construction, texture mapping and other processes are performed to generate a real-life 3D model. At the same time, the real-life 3D model adopts an LOD level of detail model and is output in blocks according to a certain grid interval, including commonly used 3D model formats such as OSGB, OBJ, and DAE. Since the above processes are all completed by existing oblique photography 3D modeling software, they will not be repeated here.

[0075] Figure 8 This is a schematic diagram of the structure of a drone photography and reconstruction device for fine building facade modeling according to the present invention. Figure 8 As shown, the present invention provides an unmanned aerial vehicle shooting and reconstruction device for fine modeling of building facades, comprising:

[0076] The initial model building unit 801 is used to use the camera carried by the drone to vertically shoot the image of the building from the air, obtain the plane and elevation information of the building after photogrammetry processing, select the outer contour range of the building, and combine the elevation information (minimum safe elevation and maximum elevation) to build a rough three-dimensional framework model of the building.

[0077] Specifically, the initial model building unit 801 further includes:

[0078] The route planning module 801a plans the route of the drone according to the plane range and height of the building and the parameters of the drone, and performs aerial photography when the drone flies along the planned route.

[0079] Specifically, the plane range and height of the building to be modeled are obtained, and the route is planned based on the obtained plane range and height, combined with the focal length of the drone's camera, the image resolution of the roof, the heading overlap of adjacent photos, the lateral overlap of adjacent routes, etc., and the route planning file is imported into the drone, so that the drone can navigate according to the planned route and take aerial photos.

[0080] The photogrammetry processing module 801b is used to perform photogrammetry processing on the image data taken vertically by the drone to obtain the plane and elevation information of the building.

[0081] In a specific embodiment of the present invention, photogrammetric processing is performed on the image data taken vertically by the drone, and the plane and elevation information of the building can be obtained according to the processing results through photogrammetric processing software, such as Pix4d, Contextcapture, Photoscan and other software.

[0082] Modeling module 801c, for selecting the outer contour range of the building according to the plane information of the building, and combining the elevation information (minimum safe elevation and maximum elevation) to construct a rough three-dimensional framework model of the building

[0083] Preferably, during the shooting process, the drone also uses the real-time RTK on board to record the GPS information (latitude and longitude coordinates, geodetic height) of each photo when shooting images. Therefore, the rough three-dimensional framework model also has relatively accurate spatial coordinate information.

[0084] The building facade route planning unit 802 is used to extract the floor plan of the building according to the rough model of the building, and establish the outer boundary of the building floor plan to obtain the outer contour line of the building, and generate the horizontal or vertical drone flight path of the building facade according to the outer contour line of the building, and obtain the facade photos collected according to the drone flight path.

[0085] Specifically, the building facade route planning unit 802 further includes:

[0086] The outer contour line establishment module 802a is used to extract the outer contour line (or plane map) of the building according to the rough 3D framework model, and to obtain the outer contour line (or plane map) of the building according to the camera shooting distance H. q Expand outward to establish a buffer zone, treat the corners as arcs, and determine the shooting distance and route interval during the UAV flight based on the overlap requirements.

[0087] In a specific embodiment of the present invention, the floor plan of the building is extracted based on the rough three-dimensional framework model of the building, which can generally be divided into a circle, a regular polygon, a rectangle, an irregular polygon, and the like.

[0088] In the present invention, the distance between the drone and the building facade, i.e., the camera shooting distance (H q ), which is determined by the focal length, image resolution, and pixel size of the camera. Specifically, the camera shooting distance (H q ) and the camera image resolution (GSD), focal length (f), and pixel size (p) are related as shown in (Equation 1):

[0089]

[0090] Assume that the camera's field of view is (fov x , fov y), the photo covers the building facade area G i , when i is x, y, it represents the coverage range G in the horizontal and vertical directions respectively x , G y , the formula is as follows:

[0091]

[0092] Since the photos taken must meet certain overlap requirements, during the route planning process, the heading (vertical direction) overlap is set to o y , the lateral (horizontal) overlap is o x , corresponding to the heading overlap length O y , the lateral overlap length is O x The interval between two adjacent exposure points in the heading direction (vertical direction) is Δs, and the height difference between adjacent routes in the lateral direction (horizontal direction) is Δh, that is:

[0093]

[0094]

[0095] That is, the shooting distance during the flight of the UAV can be determined according to Δs, and Δh can be used to determine the interval between two routes.

[0096] The shooting route generating module 802b is used to generate a shooting route around the building facade according to the outer extension boundary of the building plan, the shooting distance, the route interval, and the minimum safe flight altitude and the maximum flight altitude obtained from the rough 3D framework model.

[0097] Case 1: Horizontal flight path along the building facade

[0098] Specifically, a horizontal shooting route is generated along the outer boundary of the building plan, such as Figure 4 During the shooting process, the camera angle was 0° because it was facing the facade.

[0099] Case 2: Longitudinal flight path of the building facade

[0100] Specifically, a longitudinal shooting route is generated along the outer boundary of the building plan, such as Figure 5 During the shooting process, the camera angle was 0 degrees because it was facing the facade.

[0101] For building facades with uneven surfaces, such as eaves and balconies, there may still be blind spots after the previous two shooting methods, and additional shooting is required. That is, during the vertical shooting process, adjust the camera's shooting angle of the facade to 30°~60° for additional shooting. Figure 6 shown.

[0102] The elevation photograph acquisition module 802c is used to set the elevation photographing images to be performed at equal distances or at equal times after the photographing route is generated.

[0103] When isochronous shooting is set, the shooting interval is calculated based on the set flight speed and overlap. When isochronous shooting is set, the shooting distance interval is calculated based on the set flight speed and overlap.

[0104] For the right-angle turning area, the success rate of subsequent aerial triangulation needs to be considered. Regardless of whether the photos are taken at equal times or at equal distances, the present invention needs to take three photos at the corner for transition, namely, the straight line turns to the arc, the middle of the arc, and the arc turns to the straight line. Figure 7 As shown:

[0105] The fusion processing unit 803 is used to fuse the vertically shot images and the image data shot on the building facade to perform aerial triangulation, so as to construct a relatively complete three-dimensional model of the top and facade of the building.

[0106] Specifically, the fusion processing unit 803 imports the image data of the vertical shooting and the image data of the building facade shooting into the oblique photography 3D modeling software, such as Contextcapture center, Smart3d, etc., and sets the camera parameters (focal length, etc.) of each group of photos; uses these image data to perform free network adjustment, mainly including feature point extraction, image matching, etc., and calculates the mutual position relationship between the images; if there are control points, the control points are imported into the software and punctured on the photos; the control point constraint adjustment calculation is performed again to obtain the accurate exterior orientation elements of each photo, that is, the aerial triangulation process is completed; model construction, first dense matching is performed to generate dense point cloud data, and then triangulation network construction, texture mapping and other processes are performed to generate a real-life 3D model. At the same time, the real-life 3D model adopts an LOD level of detail model and is output in blocks at a certain grid interval, including commonly used 3D model formats such as OSGB, OBJ, and DAE.

[0107] In summary, the present invention provides a drone shooting and reconstruction method and device for fine modeling of building facades. The method first uses a camera carried by a drone to shoot a building image vertically downward from the air, obtains the plane and elevation information of the building after photogrammetry processing, selects the outer contour range of the building, and constructs a rough three-dimensional framework model of the building in combination with the elevation information. Then, the floor plan of the building is extracted according to the rough model of the building, and the outer contour line of the building is obtained by establishing the outer boundary of the building floor plan. According to the outer contour line of the building, a horizontal or vertical drone flight path of the building facade is generated, and the facade shooting image collected according to the drone flight path is obtained. Finally, the vertically shot image data and the image data shot on the building facade are fused for aerial triangulation to construct a complete three-dimensional model of the top and facade of the building, thereby achieving the purpose of fine modeling of the building facade.

[0108] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person skilled in the art may modify and change the above embodiments without violating the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be as set forth in the claims.

Claims

1. A drone photography and reconstruction method for fine modeling of building facades, comprising the following steps: Step S1, using a camera carried by a drone to shoot an image of a building vertically downward from the air, obtaining the plane and elevation information of the building after photogrammetry processing, selecting the outer contour range of the building, and constructing a rough three-dimensional framework model of the building in combination with the elevation information; in, Step S1 further comprises: Step S100, planning the route of the drone according to the plane range and height of the building and combining the parameters of the drone, and taking aerial photos when the drone is flying along the planned route; Step S101, performing photogrammetry processing on the image data taken vertically by the drone to obtain the plane image and elevation information of the building and its surrounding environment; Step S102, selecting the outer contour range of the building according to the planar image of the building and its surrounding environment, and constructing a rough three-dimensional framework model of the building in combination with elevation information; Step S2, extracting the floor plan of the building according to the rough model of the building, establishing the outer boundary of the floor plan to obtain the outer contour of the building, generating the horizontal or vertical UAV flight path of the building facade according to the outer contour of the building, and obtaining the facade shooting image collected by navigating according to the UAV flight path; Wherein, step S2 further comprises: Step S200: extracting the floor plan of the building according to the rough 3D framework model, and taking the floor plan of the building according to the camera shooting distance H. q The building buffer zone is established by expanding the distance outward, and the corners are treated as arcs. The shooting distance and flight interval of the drone during flight are determined according to the overlap requirements; Step S201, generating a shooting route around the building facade according to the outer expansion boundary of the building plan, the shooting distance, the route interval, and the minimum safe flight altitude and the maximum flight altitude known from the rough three-dimensional framework model; Step S202, after the shooting route is generated, set to shoot the vertical image at equal distance or equal time; Step S3, the vertically shot image data and the building facade image data are fused for aerial triangulation to construct a complete three-dimensional model of the top and facade of the building.

2. The drone photography and reconstruction method for fine building facade modeling according to claim 1, characterized in that: During the shooting process, the drone uses the real-time RTK on board to record the spatial coordinate information of each image data when shooting images, and the rough three-dimensional framework model has the spatial coordinate information of each image data.

3. The drone photography and reconstruction method for fine building facade modeling according to claim 2, characterized in that: In step S100, the plane range and height of the building to be modeled are obtained, and the route is planned based on the obtained plane range and height, combined with the focal length of the camera carried by the drone, the image resolution of the roof, the heading overlap of adjacent photos, and the lateral overlap of adjacent routes. When the drone navigates according to the planned route, the carried camera is used to perform aerial photography to obtain vertical image data.

4. The drone photography and reconstruction method for fine building facade modeling according to claim 1, characterized in that: The camera shooting distance (H q ), which is determined by the focal length, image resolution and pixel size of the camera carried by the UAV.

5. The drone photography and reconstruction method for fine building facade modeling according to claim 4, characterized in that: In step S201 , a horizontal shooting route is generated along the outer boundary of the building plan, with the camera angle being 0°, and / or a vertical shooting route is generated along the outer boundary of the building plan, with the camera angle being 0°.

6. The drone photography and reconstruction method for fine building facade modeling according to claim 4, characterized in that: During the vertical shooting process, adjust the camera shooting angle of the vertical surface to 30°~60° for supplementary shooting.

7. The drone photography and reconstruction method for fine building facade modeling according to claim 4, characterized in that: In step S202, when the vehicle reaches a right-angle turn area, three photos are taken for transition: a straight line turning into an arc, the middle of an arc, and an arc turning into a straight line.

8. A drone shooting and reconstruction device for fine modeling of building facades, comprising: The initial model building unit is used to use the camera carried by the drone to shoot the building image vertically downward from the air, obtain the plane and elevation information of the building after photogrammetry processing, select the outer contour range of the building, and build a rough three-dimensional framework model of the building in combination with the elevation information; The initial model building unit further includes: The route planning module is used to plan the route of the drone according to the plane range and height of the building and the parameters of the drone, and to take aerial photos when the drone flies along the planned route; A photogrammetry processing module is used to perform photogrammetry processing on the image data taken vertically by the drone to obtain the planar image and elevation information of the building and its surrounding environment; A modeling module, for selecting the outer contour range of the building according to the plane image of the building and the surrounding environment, and building a rough three-dimensional framework model of the building in combination with the elevation information; A building facade route planning unit is used to extract a floor plan of the building according to a rough model of the building, establish an outer boundary of the building floor plan to obtain an outer contour line of the building, generate a horizontal or vertical drone flight path of the building facade according to the outer contour line of the building, and obtain a facade shooting image collected by navigating according to the drone flight path; Among them, the building facade route planning unit further includes: The outer contour line establishment module is used to extract the floor plan of the building according to the rough three-dimensional framework model, and to obtain the floor plan of the building according to the camera shooting distance H. q The building buffer zone is established by expanding the distance outward, and the corners are treated as arcs. The shooting distance and flight interval of the drone during flight are determined according to the overlap requirements; A shooting route generation module is used to generate a shooting route around the building facade according to the outer extension boundary of the building plan, the shooting interval, the route interval, and the minimum safe flight altitude and the maximum flight altitude known from the rough three-dimensional framework model; The elevation photo acquisition module is used to set the elevation image shooting at equal distance or equal time after the shooting route is generated; The fusion processing unit is used to fuse the vertically shot images and the image data shot on the building facade to perform aerial triangulation and construct a complete three-dimensional model of the top and facade of the building.

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