A historical building surveying method and system based on drone

Abstract

The present invention provides a method and system for surveying and mapping historical buildings based on unmanned aerial vehicles, and relates to the technical field of surveying and mapping historical buildings. The method includes: obtaining the midpoint position of the bottom edges of the four sides of the historical building; obtaining four high-definition images of the historical building; determining the historical building surface that needs to be surveyed; setting a fixed point line parallel to the bottom edge of the historical building surface that needs to be surveyed at a second preset distance from the bottom edge of the historical building surface that needs to be surveyed; determining the first measurement distance and yaw angle measured by the first laser rangefinder; determining the position information of the unmanned aerial vehicle; determining the second measurement distance measured by the second laser rangefinder; determining the position information of the surveying and mapping point to be measured; and surveying and mapping the historical building according to the position information of the surveying and mapping point to be measured. According to the present invention, the historical building surface that needs to be surveyed can be determined, and the historical building can be constructed according to the positional relationship between the fixed point line and the unmanned aerial vehicle and the surveying and mapping point to be measured, thereby improving the efficiency, accuracy and safety of surveying and mapping.

Description

Technical Field

[0001] The present invention relates to the technical field of historical building surveying and mapping, and in particular to a historical building surveying and mapping method and system based on an unmanned aerial vehicle. Background Art

[0002] In the related art, CN111457905A relates to a historical building surveying and mapping method based on drones, especially for the surveying and mapping of traditional buildings and other historical buildings with many curved components and protruding irregular shapes. The drone's own positioning technology and hovering function are used, and auxiliary equipment is carried on the drone. The drone is hovered near the points to be measured in the historical building to measure the position of the points to be measured. By reading the position data of the drone or the relative data of the fixed points that have been surveyed on the ground, the accurate data of the surveying and mapping target is calculated.

[0003] CN117848303A relates to a surveying and mapping intelligent planning method and system for construction engineering, belonging to the field of surveying and mapping technology for construction engineering. This scheme obtains abnormal surveying and mapping points and normal surveying and mapping points based on the image clarity feature data information of each surveying and mapping point under different laser scanner working parameters, and configures the optimal laser scanner working parameters for each normal surveying and mapping point, and finally obtains the geographical location information of the abnormal surveying and mapping point, and optimizes the surveying and mapping point according to the geographical location information of the abnormal surveying and mapping point. This scheme can evaluate the surveying and mapping points according to the image clarity taken under different environmental characteristics, and can make the surveying and mapping data taken meet the image clarity requirements, thereby avoiding the occurrence of events where the image data does not meet the predetermined clarity requirements, thereby avoiding repeated operations of the surveying and mapping drone, and improving the working efficiency of the surveying and mapping drone.

[0004] Therefore, in the related technology, although the location information of the surveying points can be obtained, the related technology does not take into account the historical building surfaces that need to be surveyed, and the positional relationship between the fixed point line and the drone and the surveying points to be measured. That is, it is impossible to determine the historical building surfaces that need to be surveyed, and to construct historical buildings based on the positional relationship between the fixed point line and the drone and the surveying points to be measured.

[0005] The information disclosed in the background technology section of this application is only intended to deepen the understanding of the general background technology of this application, and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art. Summary of the invention

[0006] The present invention provides a method and system for surveying and mapping historical buildings based on drones, which can solve the technical problem that related technologies cannot determine the historical building surfaces that need to be surveyed, and construct historical buildings based on the positional relationship between fixed point lines and drones and surveying and mapping points to be measured.

[0007] According to a first aspect of the present invention, a method for surveying and mapping historical buildings based on an unmanned aerial vehicle is provided, comprising: obtaining the midpoint position of the bottom edges of four sides of a historical building, wherein the four sides of the historical building include the front side of the historical building, the back side of the historical building, the left side of the historical building and the right side of the historical building, and the bottom edges of the four sides of the historical building are the parts of the historical building in contact with the ground; photographing the historical building at a first preset distance from the midpoint position and a first preset height by a high-definition camera arranged on the unmanned aerial vehicle, respectively, to obtain four high-definition images of the historical building, wherein a line connecting the high-definition camera position and the midpoint position is perpendicular to the bottom edges of the four sides of the historical building, the first preset distance is the horizontal distance between the unmanned aerial vehicle and the midpoint position when photographing, and the first preset height is the height of the unmanned aerial vehicle from the ground when photographing; determining the historical building surface to be surveyed based on the four high-definition images of the historical building; and setting a fixed point line parallel to the bottom edge of the historical building surface to be surveyed at a second preset distance from the bottom edge of the historical building surface to be surveyed, wherein, The length of the fixed point line is the maximum width of the historical building surface to be surveyed, and the line between the midpoint of the fixed point line and the midpoint of the bottom edge of the historical building surface to be surveyed is perpendicular to the fixed point line and parallel to the ground; the navigation direction of the UAV is always parallel to the fixed point line, and the laser emitted by the first laser rangefinder arranged at the bottom of the UAV is irradiated onto the fixed point line, and the first measurement distance measured by the first laser rangefinder and the yaw angle of the first laser rangefinder are determined, wherein the first laser rangefinder only rotates left and right; the position information of the UAV is determined according to the first measurement distance and the yaw angle; when the laser emitted by the first laser rangefinder is irradiated onto the fixed point line, the second laser rangefinder arranged at the bottom of the UAV emits laser to the historical building, and the second measurement distance measured by the second laser rangefinder is determined, wherein the second laser rangefinder is facing the historical building; according to the position information of the UAV and the second measurement distance, the position information of the surveying point to be measured is determined; according to the position information of the surveying point to be measured, the historical building is surveyed.

[0008] Further, according to the four high-definition images of the historical buildings, the historical building faces that need to be mapped are determined, including: using a trained image recognition neural network model to identify the historical buildings in the four high-definition images of the historical buildings, and performing feature extraction processing to obtain architectural feature vectors of the four faces of the historical buildings, wherein the architectural feature vectors of the four faces of the historical buildings include the architectural feature vectors of the front faces of the historical buildings. , the architectural feature vector behind the historical building , the architectural feature vector to the left of the historical building and the architectural feature vector to the right of the historical building ; Determine similar historical building surfaces based on the architectural feature vectors of the four sides of the historical building; and determine the historical building surfaces that need to be surveyed based on the similar historical building surfaces.

[0009] Further, according to the architectural feature vectors of the four sides of the historical building, similar historical building faces are determined, including: according to the formula Obtained a similar historical building score of A, among which, is the i-th building feature vector, is the j-th building feature vector, for The transposed vector of is the preset similarity threshold, i and j are positive integers, and i≠j, if is the conditional function; if the similar historical building score A=0, there is no similar historical building face; if the similar historical building score A=3, the similar historical building faces are determined as the front of the historical building and the back of the historical building are similar; if the similar historical building score A=7, the similar historical building faces are determined as the left side of the historical building and the right side of the historical building are similar; if the similar historical building score A=10, the similar historical building faces are determined as the front of the historical building and the back of the historical building are similar, and the left side of the historical building and the right side of the historical building are similar; if the similar historical building score A=18, the similar historical building faces are determined as the back of the historical building, the left side of the historical building and the right side of the historical building are similar; if the similar historical building score A=30, the similar historical building faces are determined as the front of the historical building, the back of the historical building, the left side of the historical building and the right side of the historical building are all similar.

[0010] Further, according to the first measurement distance and the yaw angle, the position information of the UAV is determined, including: taking the left end point of the fixed point line as the origin, the extension direction of the fixed point line from left to right as the X-axis, the direction of the laser emitted by the second laser rangefinder as the Y-axis, and the vertical direction as the Z-axis, to establish a surveying and mapping coordinate system; obtaining the position of the point on the fixed point line irradiated by the laser emitted by the first laser rangefinder, and the horizontal distance to the left end point of the fixed point line; making the yaw angle of the first laser rangefinder 0°, and determining the irradiation point; according to the irradiation point, determining the yaw direction of the first laser rangefinder, wherein the yaw direction includes deviating inward from the fixed point line and deviating outward from the fixed point line, if the irradiation point is between the fixed point line and the bottom edges of the four sides of the historical building, then the yaw direction is deviating inward from the fixed point line, otherwise, the yaw direction is deviating outward from the fixed point line; according to the horizontal distance, the yaw direction, the first measurement distance and the yaw angle, the position information of the UAV is determined.

[0011] Further, according to the horizontal distance, the yaw direction, the first measured distance and the yaw angle, determining the position information of the UAV includes: if the yaw direction deviates inward from the fixed point line, then according to the formula Determine the drone’s location information ,in, is the horizontal distance, is the first measurement distance, is the yaw angle of the first laser rangefinder; if the yaw direction is outward from the fixed point line, then according to the formula Determine the drone’s location information .

[0012] Further, according to the position information of the drone and the second measurement distance, the position information of the surveying point to be measured is determined, including: if the yaw direction deviates inward from the fixed point line, then according to the formula Determine the location information of the surveying point to be measured ,in, is the second measured distance; if the yaw direction deviates from the fixed point line outward, then according to the formula Determine the location information of the surveying point to be measured .

[0013] Furthermore, based on the position information of the surveying and mapping points to be measured, the historical building is surveyed and mapped, including: corresponding the positions of four fixed-point lines on the ground to corresponding positions on a three-dimensional coordinate system, wherein the XOY plane of the three-dimensional coordinate system is the ground where the historical building is located; causing a drone to fly back and forth in a horizontal direction at different heights between the two ends of the fixed-point lines to obtain the position information of multiple surveying and mapping points to be measured; and constructing a three-dimensional model of the historical building based on the position information of the multiple surveying and mapping points to be measured and the corresponding positions of the four fixed-point lines on a three-dimensional coordinate system.

[0014] According to a second aspect of the present invention, a historical building surveying and mapping system based on an unmanned aerial vehicle is provided, comprising: a midpoint position module, used to obtain the midpoint position of the bottom edges of four sides of a historical building, wherein the four sides of the historical building include the front side of the historical building, the back side of the historical building, the left side of the historical building and the right side of the historical building, and the bottom edges of the four sides of the historical building are the parts of the historical building in contact with the ground; a historical building high-definition image module, used to photograph the historical building at a first preset distance from the midpoint position and a first preset height through a high-definition camera provided on the unmanned aerial vehicle, to obtain four high-definition images of the historical building, wherein: The line connecting the high-definition camera position and the midpoint position is perpendicular to the bottom edges of the four sides of the historical building; the first preset distance is the horizontal distance between the drone and the midpoint position when shooting; the first preset height is the height of the drone from the ground when shooting; the historical building surface module that needs to be surveyed is used to determine the historical building surface that needs to be surveyed based on the four high-definition images of the historical buildings; the fixed-point line module is used to set a fixed-point line parallel to the bottom edge of the historical building surface that needs to be surveyed at a second preset distance from the bottom edge of the historical building surface that needs to be surveyed, wherein the length of the fixed-point line is The maximum width of the historical building surface to be surveyed and mapped, the line between the midpoint of the fixed point line and the midpoint of the bottom edge of the historical building surface to be surveyed and mapped is perpendicular to the fixed point line and parallel to the ground; a first laser rangefinder module, used for the navigation direction of the UAV to always be parallel to the fixed point line, and to make the laser emitted by the first laser rangefinder arranged at the bottom of the UAV irradiate the fixed point line, and determine the first measurement distance measured by the first laser rangefinder and the yaw angle of the first laser rangefinder, wherein the first laser rangefinder only rotates left and right; a position information module of the UAV, used for obtaining a first measurement distance and a yaw angle of the first laser rangefinder according to the first measurement distance and the yaw angle of the first laser rangefinder A heading angle is used to determine the position information of the UAV; a second laser rangefinder module is used to cause the second laser rangefinder arranged at the bottom of the UAV to emit laser to the historical building when the laser emitted by the first laser rangefinder irradiates the fixed point line, and determine the second measurement distance measured by the second laser rangefinder, wherein the second laser rangefinder is facing the historical building; a position information module of the surveying point to be measured is used to determine the position information of the surveying point to be measured according to the position information of the UAV and the second measurement distance; a surveying module of the historical building is used to survey the historical building according to the position information of the surveying point to be measured.

[0015] Technical effect: According to the present invention, by taking high-definition images of historical buildings from four directions by drones, the historical building faces that need to be surveyed can be determined, which can reduce surveying points and improve surveying efficiency. According to the positional relationship between the fixed point line and the drone and the surveying points to be measured, that is, without contacting the historical building, the location information of the drone and the location information of the surveying points to be measured can be obtained to construct the historical building, thereby improving the accuracy and safety of surveying. When determining similar historical building faces, similar historical building faces can be determined by comparing the architectural feature vectors of the four sides of the historical building. Through different values ​​of the similar historical building score A, it can be identified which historical building faces are similar, thereby determining the historical building faces that need to be surveyed, optimizing resource allocation, reducing unnecessary duplication of work, and improving the efficiency of surveying. When determining the location information of the drone, the location information of the drone can be determined by the horizontal distance, yaw direction, first measurement distance and yaw angle. Considering the wind conditions, the location information of the drone in three-dimensional space can be determined from the two yaw direction possibilities of deviating from the fixed point line inward and deviating from the fixed point line outward, respectively, thereby improving the comprehensiveness, reliability and accuracy of the drone's location information. When determining the position information of the surveying and mapping point to be measured, the position information of the surveying and mapping point to be measured can be determined through the position information of the UAV and the second measurement distance. The position information of the surveying and mapping point to be measured in three-dimensional space can be determined based on the position information of the UAV in two yaw directions, that is, deviating inward from the fixed point line and deviating outward from the fixed point line, thereby improving the objectivity, reliability and accuracy of the position information of the surveying and mapping point to be measured.

[0016] It should be understood that the above general description and the following detailed description are exemplary and explanatory only and do not limit the present invention. Other features and aspects of the present invention will become more apparent from the following detailed description of exemplary embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other embodiments can be obtained based on these drawings without creative work.

[0018] Figure 1 A schematic diagram of a process flow of a method for surveying and mapping historical buildings based on a drone according to an embodiment of the present invention is exemplarily shown;

[0019] Figure 2 A block diagram of a historical building surveying and mapping system based on a drone according to an embodiment of the present invention is exemplarily shown. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The technical solution of the present invention is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0022] Figure 1The flowchart of the method for surveying and mapping historical buildings based on a drone according to an embodiment of the present invention is exemplarily shown, and the method comprises: step S101, obtaining the midpoint position of the bottom edges of the four sides of the historical building, wherein the four sides of the historical building include the front side of the historical building, the back side of the historical building, the left side of the historical building and the right side of the historical building, and the bottom edges of the four sides of the historical building are the parts of the historical building in contact with the ground; step S102, photographing the historical building at a first preset distance from the midpoint position and a first preset height by a high-definition camera arranged on the drone, respectively, to obtain four high-definition images of the historical building, wherein the line connecting the high-definition camera position and the midpoint position is perpendicular to the bottom edges of the four sides of the historical building, the first preset distance is the horizontal distance between the drone and the midpoint position when photographing, and the first preset height is the height of the drone from the ground when photographing; step S103, determining the historical building surface to be surveyed based on the four high-definition images of the historical building; step S104, setting a fixed point line parallel to the bottom edge of the historical building surface to be surveyed at a second preset distance from the bottom edge of the historical building surface to be surveyed, wherein , the length of the fixed-point line is the maximum width of the historical building surface to be surveyed, and the line between the midpoint of the fixed-point line and the midpoint of the bottom edge of the historical building surface to be surveyed is perpendicular to the fixed-point line and parallel to the ground; step S105, the navigation direction of the UAV is always parallel to the fixed-point line, and the laser emitted by the first laser rangefinder set at the bottom of the UAV is irradiated onto the fixed-point line, and the first measurement distance measured by the first laser rangefinder and the yaw angle of the first laser rangefinder are determined, wherein the first laser rangefinder only rotates left and right; step S106, according to the first The method comprises the following steps: firstly measuring the distance and the yaw angle to determine the position information of the UAV; step S107, when the laser emitted by the first laser rangefinder irradiates the fixed point line, the second laser rangefinder arranged at the bottom of the UAV emits a laser to the historical building, and determines the second measuring distance measured by the second laser rangefinder, wherein the second laser rangefinder is facing the historical building; step S108, determining the position information of the surveying and mapping point to be measured according to the position information of the UAV and the second measuring distance; step S109, surveying and mapping the historical building according to the position information of the surveying and mapping point to be measured.

[0023] According to the drone-based historical building surveying method of an embodiment of the present invention, high-definition images of historical buildings are taken by drones from four directions to determine the historical building surfaces that need to be surveyed, which can reduce surveying points and improve surveying efficiency. According to the positional relationship between the fixed point line and the drone and the surveying points to be measured, that is, without contacting the historical buildings, the position information of the drone and the position information of the surveying points to be measured can be obtained, the historical buildings can be constructed, and the surveying accuracy and safety can be improved.

[0024] According to one embodiment of the present invention, in step S101, the parts of the four sides of the historical building that are in contact with the ground are the bottom edges, which are the basic parts of the historical building, the lower edge of the facade of the historical building, and are in contact with the ground. The midpoint position refers to the center position between the two ends of the bottom edge, that is, the position of the point obtained by dividing the length of the bottom edge into two.

[0025] According to one embodiment of the present invention, in step S102, shooting is performed by a high-definition camera carried by a drone. During the shooting process, the flight position and height of the drone need to be accurately controlled, that is, the drone hovers at a first preset distance from the midpoint position of the bottom edges of the four sides of the historical building, and its hovering height reaches the first preset height. The line connecting the high-definition camera position and the midpoint position is perpendicular to the bottom edges of the four sides of the historical building. The first preset distance is the straight-line distance between the horizontal position and the center position of the drone when shooting, that is, the first preset distance is the horizontal distance between the drone and the midpoint position when shooting. The first preset height is the height of the drone from the ground when shooting. After the drone reaches the position, the high-definition camera is used to shoot the four sides of the historical building (the front of the historical building, the back of the historical building, the left side of the historical building, and the right side of the historical building). By shooting at the corresponding positions, high-definition images of the historical building from four different angles are obtained.

[0026] According to an embodiment of the present invention, in step S103, the historical building surfaces that need to be surveyed are determined based on the four high-definition images of the historical buildings.

[0027] According to an embodiment of the present invention, step S103 includes: using a trained image recognition neural network model to identify the historical building in the four high-definition images of the historical building, and performing feature extraction processing to obtain the architectural feature vectors of the four sides of the historical building, wherein the architectural feature vectors of the four sides of the historical building include the architectural feature vectors of the front of the historical building. , the architectural feature vector behind the historical building , the architectural feature vector to the left of the historical building and the architectural feature vector to the right of the historical building ; Determine similar historical building surfaces based on the architectural feature vectors of the four sides of the historical building; and determine the historical building surfaces that need to be surveyed based on the similar historical building surfaces.

[0028] According to one embodiment of the present invention, the image recognition neural network model can be a convolutional neural network model. The four high-definition images of historical buildings are processed by the trained image recognition neural network model, that is, the historical buildings are identified, the features of the historical buildings are extracted therefrom, and the architectural feature vectors of the four sides of the historical buildings are obtained. By comparing the architectural feature vectors of the four sides of the historical buildings, the similarities between the faces of the historical buildings can be determined. Based on the similar historical building faces, the historical building faces that need to be surveyed are determined. For example, the architectural features of the front of the historical building are the same as those of the back, left and right of the historical building. Only the surveying points of the front of the historical building need to be measured, and the other three sides are surveyed according to the style of the front of the historical building, thereby saving a lot of measurement work.

[0029] According to an embodiment of the present invention, determining similar historical building faces according to the architectural feature vectors of the four faces of the historical building includes: obtaining a similar historical building score A according to formula (1);

[0030] (1),

[0031] in, is the i-th building feature vector, is the j-th building feature vector, for The transposed vector of is the preset similarity threshold, i and j are positive integers, and i≠j, if is the conditional function; if the similar historical building score A=0, there is no similar historical building face; if the similar historical building score A=3, the similar historical building faces are determined as the front of the historical building and the back of the historical building are similar; if the similar historical building score A=7, the similar historical building faces are determined as the left side of the historical building and the right side of the historical building are similar; if the similar historical building score A=10, the similar historical building faces are determined as the front of the historical building and the back of the historical building are similar, and the left side of the historical building and the right side of the historical building are similar; if the similar historical building score A=18, the similar historical building faces are determined as the back of the historical building, the left side of the historical building and the right side of the historical building are similar; if the similar historical building score A=30, the similar historical building faces are determined as the front of the historical building, the back of the historical building, the left side of the historical building and the right side of the historical building are all similar.

[0032] According to one embodiment of the present invention, in formula (1), is the similarity between the i-th building feature vector and the j-th building feature vector. The greater the similarity, the more similar the i-th building feature vector and the j-th building feature vector are. For example, when i=1 and j=2, the greater the similarity, the more similar the front of the historical building is to the back of the historical building. It indicates that when the similarity between the i-th building feature vector and the j-th building feature vector is greater than or equal to the preset similarity threshold, the conditional function value is i, otherwise, the conditional function value is 0. By summing the conditional functions corresponding to each pair of building feature vectors, the score of similar historical buildings can be obtained.

[0033] According to one embodiment of the present invention, different similar historical building scoring A values ​​can be used to determine which building faces are similar. For example, A=0 means that there are no similar historical building faces, and the historical building faces that need to be surveyed are the four sides of the historical building; A=3 means that the front and back of the historical building are similar, and the historical building faces that need to be surveyed are the front (back) side of the historical building, the left side of the historical building, and the right side of the historical building; A=7 means that the left side of the historical building is similar to the right side of the historical building, and the historical building faces that need to be surveyed are the front, back, and right side of the historical building. The left (right) side of the historical building; A=10, indicating that the front of the historical building is similar to the back of the historical building, and the left side of the historical building is similar to the right side of the historical building, so the historical building sides that need to be surveyed are the front (back) side of the historical building and the left (right) side of the historical building; A=18, indicating that the back, left side and right side of the historical building are similar, so the historical building sides that need to be surveyed are the front of the historical building and the back (left, right) side of the historical building; A=30, indicating that all four sides of the historical building are similar, so the historical building sides that need to be surveyed are the front (back, left, right) side of the historical building. The above are common similarities of the four sides of the historical building. As for special cases, for example, the front of the historical building is similar to the right side of the historical building, and the left side of the historical building is similar to the back of the historical building, it is difficult to find examples, so they are not described.

[0034] In this way, similar historical building faces can be determined by comparing the architectural feature vectors of the four sides of the historical buildings. Through different values ​​of the similar historical building score A, it is possible to identify which historical building faces are similar, thereby determining the historical building faces that need to be surveyed, optimizing resource allocation, reducing unnecessary duplication of work, and improving the efficiency of surveying.

[0035] According to one embodiment of the present invention, in step S104, the line between the midpoint of the fixed point line and the midpoint of the bottom edge of the historical building surface to be surveyed is perpendicular to the fixed point line and parallel to the ground, that is, the fixed point line and the bottom edge of the historical building surface to be surveyed are on the same horizontal plane (ground). The length of the fixed point line is the maximum width of the historical building surface to be surveyed, which means that the length of the fixed point line will not be less than the width of the historical building surface to be surveyed on the horizontal plane, and can cover the historical building surface to be surveyed.

[0036] According to one embodiment of the present invention, in step S105, in the absence of external force intervention, the flight trajectory of the drone is along the direction of the fixed point line, but when hovering for measurement, it is possible that wind will arise and the drone will deviate from the fixed point line, but the navigation direction of the drone is always parallel to the fixed point line. A first laser rangefinder is installed at the bottom of the drone for emitting laser for distance measurement. When the drone is hovering for measurement, the first laser rangefinder rotates left and right relative to the navigation direction so that the emitted laser is accurately irradiated onto the fixed point line, and the first measurement distance and yaw angle of the first laser rangefinder are determined at this time. The yaw angle is used to describe the angle at which the first laser rangefinder rotates left or right.

[0037] According to an embodiment of the present invention, in step S106, the position information of the UAV is determined according to the first measured distance and the yaw angle.

[0038] According to one embodiment of the present invention, step S106 includes: establishing a surveying and mapping coordinate system with the left end point of the fixed-point line as the origin, the extension direction of the fixed-point line from left to right as the X-axis, the direction of the laser emitted by the second laser rangefinder as the Y-axis, and the vertical direction as the Z-axis; obtaining the position of the point on the fixed-point line irradiated by the laser emitted by the first laser rangefinder, and the horizontal distance to the left end point of the fixed-point line; making the yaw angle of the first laser rangefinder 0°, and determining the irradiation point; determining the yaw direction of the first laser rangefinder according to the irradiation point, wherein the yaw direction includes deviating inward from the fixed-point line and deviating outward from the fixed-point line, if the irradiation point is between the fixed-point line and the bottom edges of the four sides of the historical building, then the yaw direction is deviating inward from the fixed-point line, otherwise, the yaw direction is deviating outward from the fixed-point line; determining the position information of the drone according to the horizontal distance, the yaw direction, the first measured distance and the yaw angle.

[0039] According to one embodiment of the present invention, the position of the point on the fixed point line irradiated by the laser emitted by the first laser rangefinder, and the horizontal distance to the left end point of the fixed point line can be measured by a distance measuring instrument (for example, a radar rangefinder). The horizontal distance is the coordinate value of the drone on the X-axis, reflecting the position of the drone on the horizontal plane. When the yaw angle of the first laser rangefinder is 0° (that is, the laser of the first laser rangefinder is perpendicular to the ground), the irradiation point is determined. If the irradiation point is between the fixed point line and the bottom edge of the four sides of the historical building, the yaw direction of the first laser rangefinder is deviated from the fixed point line inward (that is, deviated toward the historical building), otherwise, the yaw direction of the first laser rangefinder is deviated from the fixed point line outward. According to the horizontal distance, yaw direction, first measured distance and yaw angle, the position information of the drone is determined.

[0040] According to an embodiment of the present invention, determining the position information of the drone according to the horizontal distance, the yaw direction, the first measured distance and the yaw angle includes: if the yaw direction deviates inward from the fixed point line, determining the position information of the drone according to formula (2) ,

[0041] (2),

[0042] in, is the horizontal distance, is the first measurement distance, is the yaw angle of the first laser rangefinder; if the yaw direction is outward from the fixed point line, the position information of the UAV is determined according to formula (3): ,

[0043] (3);

[0044] According to one embodiment of the present invention, in formula (2), the horizontal distance from the position of the point on the fixed point line irradiated by the laser emitted by the first laser rangefinder to the left end point of the fixed point line is is the projection length of the drone's position in the X-axis direction in the surveying coordinate system, that is, the coordinate value of the drone on the X-axis, reflecting the drone's position on the horizontal plane. The distance from the drone to the point on the fixed point line where the laser emitted by the first laser rangefinder irradiates is the first measured distance measured by the first laser rangefinder. The yaw direction is inward from the fixed point line, so the drone is between the fixed point line and the bottom edge of the four sides of the historical building, that is, the drone is in the positive half area of ​​the Y axis, so, It is the projection length of the UAV's position in the Y-axis direction in the surveying coordinate system, that is, the coordinate value of the UAV on the Y-axis. is the projection length of the drone's position in the Z-axis direction in the surveying coordinate system, that is, the coordinate value of the drone on the Z-axis. From the above three coordinate values, we can get the drone's position information when the yaw direction is inward from the fixed point line. In formula (3), the yaw direction is outward from the fixed point line, so the drone is not between the fixed point line and the bottom edge of the four sides of the historical building, but on the other side of the fixed point line (X axis), that is, the negative half area of ​​the Y axis. Therefore, is the coordinate value of the drone on the Y axis. The coordinate value of the drone on the X and Z axes when the yaw direction is inward from the fixed point line is the same as the coordinate value of the drone on the X and Z axes when the yaw direction is outward from the fixed point line.

[0045] In this way, the position information of the UAV can be determined through the horizontal distance, yaw direction, the first measured distance and the yaw angle. Taking into account the wind conditions, the position information of the UAV in three-dimensional space can be determined from the two possible yaw directions of deviating inward from the fixed point line and deviating outward from the fixed point line, thereby improving the comprehensiveness, reliability and accuracy of the UAV's position information.

[0046] According to one embodiment of the present invention, in step S107, after the laser emitted by the first laser rangefinder successfully irradiates the fixed point line, the second laser rangefinder at the bottom of the drone is activated and starts to emit laser toward the historical building. The second laser rangefinder is aimed at the historical building, which can improve the accuracy of the second measurement distance measurement.

[0047] According to an embodiment of the present invention, in step S108, the position information of the surveying point to be measured is determined according to the position information of the drone and the second measurement distance.

[0048] According to an embodiment of the present invention, the position information of the surveying point to be measured is determined according to the position information of the drone and the second measurement distance, including: if the yaw direction is inward from the fixed point line, the position information of the surveying point to be measured is determined according to formula (4): ,

[0049] (4),

[0050] in, is the second measurement distance; if the yaw direction is outward from the fixed point line, the position information of the surveying point to be measured is determined according to formula (5): ,

[0051] (5);

[0052] According to one embodiment of the present invention, in formula (4), the distance from the drone to the surveying point to be measured on the historical building is the second measurement distance measured by the second laser rangefinder, that is, the second measurement distance is the relative distance between the surveying point to be measured and the drone in the Y-axis direction in the surveying coordinate system. The yaw direction is inward from the fixed point line, and the drone is between the fixed point line and the bottom edges of the four sides of the historical building, that is, the drone is in the positive half area of ​​the Y-axis. Therefore, is the coordinate value of the surveying point to be measured on the Y axis. The surveying point to be measured and the drone are at the same height and the same horizontal line. Therefore, the coordinate values ​​of the surveying point to be measured on the X and Z axes are the same as the coordinate values ​​of the drone on the X and Z axes. Therefore, the position information of the surveying point to be measured can be obtained when the yaw direction deviates from the fixed point line inward. In formula (5), the yaw direction deviates from the fixed point line outward, so the drone is not between the fixed point line and the bottom edge of the four sides of the historical building, but in the negative half area of ​​the Y axis. Therefore, is the difference between the second measured distance and the coordinate value of the drone on the Y axis, which is the projection length of the position of the surveying point to be measured in the Y axis direction in the surveying coordinate system, that is, the coordinate value of the surveying point to be measured on the Y axis. Similarly, the position information of the surveying point to be measured can be obtained when the yaw direction deviates from the fixed point line outward.

[0053] In this way, the position information of the surveying and mapping point to be measured can be determined through the position information of the UAV and the second measurement distance. The position information of the surveying and mapping point to be measured in three-dimensional space can be determined by the position information of the UAV in two yaw directions, that is, deviating inward from the fixed point line and deviating outward from the fixed point line, thereby improving the objectivity, reliability and accuracy of the position information of the surveying and mapping point to be measured.

[0054] According to an embodiment of the present invention, in step S109, the historical building is surveyed and mapped based on the position information of the surveying and mapping points to be surveyed.

[0055] According to one embodiment of the present invention, step S109 includes: corresponding the positions of the four fixed-point lines on the ground to corresponding positions on a three-dimensional coordinate system, wherein the XOY plane of the three-dimensional coordinate system is the ground where the historical building is located; causing the drone to fly back and forth in a horizontal direction at different heights between the two ends of the fixed-point lines to obtain position information of multiple surveying and mapping points to be measured; and constructing a three-dimensional model of the historical building based on the position information of the multiple surveying and mapping points to be measured and the corresponding positions of the four fixed-point lines in a three-dimensional coordinate system.

[0056] According to one embodiment of the present invention, a new three-dimensional coordinate system is established on the ground where the historical building is located, and the positions of the four fixed-point lines on the ground are corresponded to the corresponding positions on the new three-dimensional coordinate system. Then, the XOY plane of the new three-dimensional coordinate system is the ground where the historical building is located. The UAV flies back and forth at different heights along the horizontal direction between the two ends of the four fixed-point lines, and can cover all areas of the historical building. During the flight of the UAV, a laser rangefinder is used to obtain the position information of multiple surveying and mapping points to be measured. The position information of the surveying and mapping points to be measured is all relative to the fixed-point lines. Therefore, these relative position information can be combined with the corresponding positions of the four fixed-point lines in the new three-dimensional coordinate system to perform data processing, which involves the organization of point cloud data and the construction of building models, thereby completing the reconstruction of the three-dimensional model of the historical building.

[0057] According to the historical building surveying method based on drones of the embodiment of the present invention, the drones take high-definition images of historical buildings from four directions to determine the historical building faces that need to be surveyed, which can reduce surveying points and improve surveying efficiency. According to the positional relationship between the fixed point line and the drone and the surveying points to be measured, that is, without contacting the historical buildings, the position information of the drone and the position information of the surveying points to be measured can be obtained to construct the historical buildings, thereby improving the surveying accuracy and safety. When determining similar historical building faces, similar historical building faces can be determined by comparing the architectural feature vectors of the four sides of the historical buildings. Through different values ​​of the similar historical building score A, it can be identified which historical building faces are similar, thereby determining the historical building faces that need to be surveyed, optimizing resource allocation, reducing unnecessary duplication of work, and improving the surveying efficiency. When determining the position information of the drone, the position information of the drone can be determined by the horizontal distance, yaw direction, first measurement distance and yaw angle. Considering the wind conditions, the position information of the drone in three-dimensional space can be determined from the two yaw direction possibilities of deviating from the fixed point line inward and deviating from the fixed point line outward, respectively, thereby improving the comprehensiveness, reliability and accuracy of the drone's position information. When determining the position information of the surveying and mapping point to be measured, the position information of the surveying and mapping point to be measured can be determined through the position information of the UAV and the second measurement distance. The position information of the surveying and mapping point to be measured in three-dimensional space can be determined based on the position information of the UAV in two yaw directions, that is, deviating inward from the fixed point line and deviating outward from the fixed point line, thereby improving the objectivity, reliability and accuracy of the position information of the surveying and mapping point to be measured.

[0058] Figure 2A block diagram of a historical building surveying and mapping system based on a drone according to an embodiment of the present invention is exemplarily shown, wherein the system comprises: a midpoint position module, used to obtain the midpoint position of the bottom edges of four sides of a historical building, wherein the four sides of the historical building include the front side of the historical building, the back side of the historical building, the left side of the historical building and the right side of the historical building, and the bottom edges of the four sides of the historical building are the parts of the historical building in contact with the ground; a historical building high-definition image module, used to photograph the historical building at a first preset distance from the midpoint position and at a first preset height through a high-definition camera provided on the drone, to obtain four high-definition images of the historical building. The image is as follows: the line connecting the high-definition camera position and the midpoint position is perpendicular to the bottom edges of the four sides of the historical building; the first preset distance is the horizontal distance between the drone and the midpoint position when shooting; and the first preset height is the height of the drone from the ground when shooting; the historical building surface module to be surveyed is used to determine the historical building surface to be surveyed based on the four high-definition images of the historical buildings; the fixed point line module is used to set a fixed point line parallel to the bottom edge of the historical building surface to be surveyed at a second preset distance from the bottom edge of the historical building surface to be surveyed, wherein the fixed point line The length is the maximum width of the historical building surface to be surveyed and mapped, and the line between the midpoint of the fixed-point line and the midpoint of the bottom edge of the historical building surface to be surveyed and mapped is perpendicular to the fixed-point line and parallel to the ground; a first laser rangefinder module is used to ensure that the navigation direction of the UAV is always parallel to the fixed-point line, and to make the laser emitted by the first laser rangefinder set at the bottom of the UAV irradiate the fixed-point line, and determine the first measurement distance measured by the first laser rangefinder and the yaw angle of the first laser rangefinder, wherein the first laser rangefinder only rotates left and right; a position information module of the UAV is used to obtain the first measurement distance and the yaw angle of the first laser rangefinder according to the first measurement distance and the The yaw angle is used to determine the position information of the UAV; a second laser rangefinder module is used for, when the laser emitted by the first laser rangefinder is irradiated onto the fixed point line, the second laser rangefinder arranged at the bottom of the UAV emits laser to the historical building, and determines the second measurement distance measured by the second laser rangefinder, wherein the second laser rangefinder is facing the historical building; a position information module of the surveying and mapping point to be measured is used to determine the position information of the surveying and mapping point to be measured according to the position information of the UAV and the second measurement distance; a surveying and mapping module of the historical building is used to survey and map the historical building according to the position information of the surveying and mapping point to be measured.

[0059] It should be understood by those skilled in the art that the embodiments of the present invention described above and shown in the accompanying drawings are only examples and do not limit the present invention. The purpose of the present invention has been fully and effectively achieved. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments, and the embodiments of the present invention may be deformed or modified in any way without departing from the principles.

Claims

1. A method for surveying and mapping historical buildings based on drones, characterized in that: include: Obtain the midpoint position of the bottom edges of the four sides of the historical building, wherein the four sides of the historical building include the front side of the historical building, the back side of the historical building, the left side of the historical building and the right side of the historical building, and the bottom edges of the four sides of the historical building are the parts of the historical building that are in contact with the ground; photograph the historical building at a first preset distance from the midpoint position and a first preset height through a high-definition camera set on a drone, respectively, to obtain four high-definition images of the historical building, wherein a line connecting the high-definition camera position and the midpoint position is perpendicular to the bottom edges of the four sides of the historical building, the first preset distance is the horizontal distance between the drone and the midpoint position when shooting, and the first preset height is the height of the drone from the ground when shooting; determine the historical building surface that needs to be surveyed based on the four high-definition images of the historical building; set a fixed-point line parallel to the bottom edge of the historical building surface that needs to be surveyed at a second preset distance from the bottom edge of the historical building surface that needs to be surveyed, wherein the length of the fixed-point line is the length of the historical building surface that needs to be surveyed. the maximum width of the historical building surface, the line between the midpoint of the fixed point line and the midpoint of the bottom edge of the historical building surface to be surveyed is perpendicular to the fixed point line and parallel to the ground; the navigation direction of the UAV is always parallel to the fixed point line, and the laser emitted by the first laser rangefinder arranged at the bottom of the UAV is irradiated on the fixed point line, and the first measurement distance measured by the first laser rangefinder and the yaw angle of the first laser rangefinder are determined, wherein the first laser rangefinder only rotates left and right; the position information of the UAV is determined according to the first measurement distance and the yaw angle; when the laser emitted by the first laser rangefinder is irradiated on the fixed point line, the second laser rangefinder arranged at the bottom of the UAV emits laser to the historical building, and the second measurement distance measured by the second laser rangefinder is determined, wherein the second laser rangefinder is facing the historical building; according to the position information of the UAV and the second measurement distance, the position information of the surveying point to be measured is determined; according to the position information of the surveying point to be measured, the historical building is surveyed and mapped.

2. The method for surveying and mapping historical buildings based on drones according to claim 1 is characterized in that: Determining the historical building faces that need to be mapped based on the four high-definition images of the historical buildings, including: identifying the historical buildings in the four high-definition images of the historical buildings through a trained image recognition neural network model, and performing feature extraction processing to obtain architectural feature vectors of the four faces of the historical buildings, wherein the architectural feature vectors of the four faces of the historical buildings include the architectural feature vectors of the front faces of the historical buildings , the architectural feature vector behind the historical building , the architectural feature vector to the left of the historical building and the architectural feature vector to the right of the historical building ; Determine similar historical building surfaces based on the architectural feature vectors of the four sides of the historical building; and determine the historical building surfaces that need to be surveyed based on the similar historical building surfaces.

3. The method for surveying and mapping historical buildings based on drones according to claim 2 is characterized in that: Determine similar historical building faces according to the architectural feature vectors of the four faces of the historical building, including: according to the formula Obtained a similar historical building score of A, among which, is the i-th building feature vector, is the j-th building feature vector, for The transposed vector of is the preset similarity threshold, i and j are positive integers, and i≠j, if is the conditional function; if the similar historical building score A=0, there is no similar historical building face; if the similar historical building score A=3, the similar historical building faces are determined as the front of the historical building and the back of the historical building are similar; if the similar historical building score A=7, the similar historical building faces are determined as the left side of the historical building and the right side of the historical building are similar; if the similar historical building score A=10, the similar historical building faces are determined as the front of the historical building and the back of the historical building are similar, and the left side of the historical building and the right side of the historical building are similar; if the similar historical building score A=18, the similar historical building faces are determined as the back of the historical building, the left side of the historical building and the right side of the historical building are similar; if the similar historical building score A=30, the similar historical building faces are determined as the front of the historical building, the back of the historical building, the left side of the historical building and the right side of the historical building are all similar.

4. The method for surveying and mapping historical buildings based on drones according to claim 1 is characterized in that: Determine the position information of the UAV according to the first measurement distance and the yaw angle, including: establish a surveying and mapping coordinate system with the left end point of the fixed point line as the origin, the extension direction of the fixed point line from left to right as the X-axis, the direction of the laser emitted by the second laser rangefinder as the Y-axis, and the vertical direction as the Z-axis; obtain the horizontal distance from the position of the point on the fixed point line irradiated by the laser emitted by the first laser rangefinder to the left end point of the fixed point line; make the yaw angle of the first laser rangefinder 0° to determine the irradiation point; determine the yaw direction of the first laser rangefinder according to the irradiation point, wherein the yaw direction includes deviating inward from the fixed point line and deviating outward from the fixed point line, if the irradiation point is between the fixed point line and the bottom edges of the four sides of the historical building, then the yaw direction is deviating inward from the fixed point line, otherwise, the yaw direction is deviating outward from the fixed point line; determine the position information of the UAV according to the horizontal distance, the yaw direction, the first measurement distance and the yaw angle.

5. The method for surveying and mapping historic buildings based on drones according to claim 4 is characterized in that: Determine the position information of the UAV according to the horizontal distance, the yaw direction, the first measured distance and the yaw angle, including: if the yaw direction deviates inward from the fixed point line, then according to the formula Determine the drone’s location information ,in, is the horizontal distance, is the first measurement distance, is the yaw angle of the first laser rangefinder; if the yaw direction is outward from the fixed point line, then according to the formula Determine the drone’s location information .

6. The method for surveying and mapping historical buildings based on drones according to claim 5 is characterized in that: According to the position information of the UAV and the second measurement distance, the position information of the surveying point to be measured is determined, including: if the yaw direction deviates inward from the fixed point line, according to the formula Determine the location information of the surveying point to be measured ,in, is the second measured distance; if the yaw direction deviates from the fixed point line outward, then according to the formula Determine the location information of the surveying point to be measured .

7. The method for surveying and mapping historical buildings based on drones according to claim 1, characterized in that: The historical building is surveyed and mapped according to the position information of the surveying and mapping points to be measured, including: corresponding the positions of four fixed-point lines on the ground to corresponding positions on a three-dimensional coordinate system, wherein the XOY plane of the three-dimensional coordinate system is the ground where the historical building is located; making a drone fly back and forth in a horizontal direction at different heights between the two ends of the fixed-point lines to obtain the position information of multiple surveying and mapping points to be measured; and constructing a three-dimensional model of the historical building according to the position information of the multiple surveying and mapping points to be measured and the corresponding positions of the four fixed-point lines on a three-dimensional coordinate system.

8. A drone-based historical building surveying system for executing the drone-based historical building surveying method according to any one of claims 1 to 7, characterized in that: include: A midpoint position module is used to obtain the midpoint position of the bottom edges of the four sides of the historical building, wherein the four sides of the historical building include the front side of the historical building, the back side of the historical building, the left side of the historical building and the right side of the historical building, and the bottom edges of the four sides of the historical building are the parts of the historical building that are in contact with the ground; a high-definition image module of a historical building is used to photograph the historical building at a first preset distance from the midpoint position and a first preset height through a high-definition camera set on a drone, and obtain four high-definition images of the historical building, wherein the line connecting the high-definition camera position and the midpoint position is perpendicular to the bottom edges of the four sides of the historical building, the first preset distance is the horizontal distance between the drone and the midpoint position when shooting, and the first preset height is the height of the drone from the ground when shooting; a module for the historical building surface to be surveyed and mapped is used to determine the historical building surface to be surveyed and mapped based on the four high-definition images of the historical building; a fixed-point line module is used to set a fixed-point line parallel to the bottom edge of the historical building surface to be surveyed and mapped at a second preset distance from the bottom edge of the historical building surface to be surveyed and mapped, wherein the length of the fixed-point line is the maximum width of the historical building surface to be surveyed and mapped , the line between the midpoint of the fixed point line and the midpoint of the bottom edge of the historical building surface to be surveyed is perpendicular to the fixed point line and parallel to the ground; the first laser rangefinder module is used to ensure that the navigation direction of the drone is always parallel to the fixed point line, and to irradiate the laser emitted by the first laser rangefinder set at the bottom of the drone onto the fixed point line, and to determine the first measurement distance measured by the first laser rangefinder and the yaw angle of the first laser rangefinder, wherein the first laser rangefinder only rotates left and right; the position information module of the drone is used to determine the position of the drone according to the first measurement distance and the yaw angle. a second laser rangefinder module, used for, when the laser emitted by the first laser rangefinder is irradiated onto the fixed point line, the second laser rangefinder arranged at the bottom of the drone emits laser to the historical building, and determines the second measurement distance measured by the second laser rangefinder, wherein the second laser rangefinder is facing the historical building; a position information module of the surveying and mapping point to be measured, used for determining the position information of the surveying and mapping point to be measured according to the position information of the drone and the second measurement distance; a surveying and mapping module of the historical building, used for surveying and mapping the historical building according to the position information of the surveying and mapping point to be measured.

Images