Ground control method for bridge pier top accurate modeling

Abstract

According to the ground control method for accurate modeling of the bridge pier top, established external control points are actually pier top feature points, on one hand, the precision is improved, on the other hand, the acquisition range of field images or point clouds only comprises the local part of the pier top, and the influence of the surrounding environment of the pier on the precision of a three-dimensional model of the pier is avoided; mutual influence between the two steps of the field control scheme and the pier top image or three-dimensional point cloud acquisition process is small, relative independence is high, and field work can be flexibly organized according to instrument configuration and field conditions. All the steps involved in the scheme are classical measurement work and can be easily implemented by common measurement technicians. The interference between the operation of the unmanned aerial vehicle for conveying the pier top artificial elevation proportion control mark and the operation of the unmanned aerial vehicle for pier top photographing or scanning is small, and organization of pier top photographing or scanning operation is facilitated. The invention is suitable for piers with any height, and is also suitable for land piers and water piers.

Description

Technical Field

[0001] The invention relates to the technical field of bridge pier construction, and in particular to a ground control method for accurate modeling of bridge pier tops. Background Art

[0002] Based on visual measurement, close-range photogrammetry, oblique photogrammetry or 3D laser scanning and other technical means, an accurate 3D model of the bridge pier top can be established, and the necessary plane and elevation measurement work before the bridge pier beam can be completed based on the 3D model. In order to achieve this goal, high-precision control must be carried out in the field of data collection or in the office after the collection is completed to incorporate the 3D model into the engineering coordinate system.

[0003] At present, the technical means is generally to establish a number of control points on the ground to establish control. Although this technical solution is simple, it has several shortcomings: 1) For the three-dimensional model of the pier top, its accuracy is not high. Especially in the case of high piers. It is common for the actual bridge piers to be more than 20m high. In the western mountainous areas, many will exceed 50m or even 100m. 2) For underwater piers, this solution cannot be implemented.

[0004] In the patent for "High Pier Measurement Method" (application number 202211540035.5), it is proposed to use drones to transport two automatically arranged prism devices to the top of the pier to establish effective local control. Although this technical solution may meet the accuracy requirements and can be applied to piers of various heights. However, this method involves the lifting of the automatic leveling base, which is technically difficult, requires a high level of pilots, and has certain requirements for on-site crosswinds; the automatic leveling base is heavy (>4kg), and a high-power drone is required to perform the lifting task; in addition, two drones are required to lift at the same time, which poses difficulties in drone route control and scheduling. The two drones are close in the air, and the risk is high due to uncontrollable factors such as air turbulence.

[0005] Therefore, it is necessary to develop a ground control method for accurate modeling of bridge pier tops to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to design a ground control method for accurate modeling of bridge pier tops in order to solve the above problems.

[0007] The present invention achieves the above-mentioned purpose through the following technical solutions: A ground control method for accurate modeling of bridge pier tops, comprising the steps of: S1: Determine two temporary control points A and B on the ground near the bridge pier. The top of the bridge pier top support stone can be seen from the control points A and B. Select four or eight feature points. Two rectangular support stones are set on the bridge pier top. When four feature points are selected, the four feature points are the four top corner points of the rectangle surrounded by the two rectangular support stones. When eight feature points are selected, the eight feature points include the four top corner points of the two rectangular support stones. The distance between the two control points shall not be less than 20m. S2: Select the control point C of the bridge control network near the pier as the known coordinates and measure the plane coordinates of points A and B; S3: After setting up the total station at control point A, use a fixed height prism base to place prisms at control points B and C to observe the horizontal angles and vertical angles of control points B, C, and all selected pier top feature points; S4: After setting up the total station at control point B, use a fixed height prism base to place prisms at control points A and C to observe the horizontal angles and vertical angles of control points A, C, and all selected pier top feature points; if two total stations are used for synchronous measurement, steps S2-S3 can be performed simultaneously; S5: solving the plane and elevation of feature points; S51, using the horizontal angles of the control point A, the control point B and the characteristic point, and the plane coordinates of the control point A and the control point B, the plane coordinates of the bridge characteristic point are calculated according to the principle of forward intersection; S52, and reversely calculate the horizontal distances from the control point A and the control point B to each feature point; S53, using the vertical angles and distances from control point A and control point B to point C, as well as the vertical angles and horizontal distances from control point A and control point B to the feature point, measuring the prism height may introduce errors and affect the measurement efficiency due to factors such as uneven ground on site and operator operation errors, and adopt a trigonometric height measurement method without measuring the prism to obtain the elevation of each feature point; S6: Before collecting the pier top image or 3D point cloud in the field, an artificial elevation scale control mark is placed on the pier top by using a drone. Then, when collecting the pier top image or 3D point cloud in the field, the artificial elevation scale control mark exists in the pier top image or 3D point cloud. S7: The plane and elevation coordinates of the selected feature points are obtained. During the three-dimensional model establishment process, plane position and plane scale control, as well as elevation control, are provided. The pier top mark can provide scale control in the elevation direction, thereby meeting the field control requirements for the establishment of the three-dimensional model of the pier top.

[0008] The beneficial effects of the present invention are: (1) High precision; The external control points established in the present invention are actually characteristic points on the pier top (generally the upper corner points of the supporting cushion stones). On the one hand, this helps to improve the accuracy. On the other hand, it allows the acquisition range of field images or point clouds to only include the pier top, which helps to avoid the influence of the surrounding environment of the pier on the accuracy of the pier three-dimensional model.

[0009] (2) Easy to implement; The field control scheme proposed in the present invention and the pier top image or three-dimensional point cloud acquisition process have little mutual influence and high relative independence. The field work can be flexibly organized according to the instrument configuration and on-site conditions.

[0010] Each step involved in this scheme is classic measurement work and can be easily implemented by general measurement technicians.

[0011] The UAV operation of transporting artificial elevation proportional control marks on the pier top has less interference with the UAV operation of photographing or scanning the pier top, which is conducive to the organization of the photography or scanning operation on the pier top.

[0012] It is suitable for bridge piers of any height, and is applicable to both land piers and underwater piers.

[0013] (3) Reliable technology; Each step involved in the present invention is a mature technology and the method is reliable; there is no need to set a control point on the pier top, thus avoiding the safety risk of manual control points on the pier top in traditional operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the pier top control point; Figure 2 This is a schematic diagram of the artificial elevation ratio control sign. DETAILED DESCRIPTION

[0015] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions 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 part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0016] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0017] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0018] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use, or are directions or positional relationships commonly understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0019] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0020] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings.

[0022] A ground control method for accurate modeling of bridge pier tops, comprising the steps of: S1: Determine two temporary control points A and B on the ground near the bridge pier. The top of the bridge pier top support stone can be seen from the control points A and B. Select four or eight feature points. Two rectangular support stones are set on the bridge pier top. When four feature points are selected, the four feature points are the four top corner points of the rectangle surrounded by the two rectangular support stones. When eight feature points are selected, the eight feature points include the four top corner points of the two rectangular support stones. The distance between the two control points shall not be less than 20m. The characteristic points can generally be selected from 4 or 2 top corner points of the left and right supporting pads in the direction of small mileage and large mileage; other clear characteristic points can also be selected according to the characteristics of the bridge itself. Generally, there are 2 or 4 characteristic points in the direction of large mileage and small mileage, and the total number is generally 4 or 8. For example Figure 2 T1, T2, T5, T6 (4 feature points) or T1, T2, T3, T4, T5, T6, T7, T8 (8 control points).

[0023] Since the outer edge of the support stone is close to the edge of the pier top, the distance is about 20cm, and the ground is undulating, so the top of the support stone can always be observed from a suitable position on the ground; S2: Select the control point C of the bridge control network near the bridge pier as the known coordinates, and measure the plane coordinates of points A and B; if there are no construction control points nearby, encrypt them based on the existing bridge construction control network; S3: After setting up the total station at control point A, use a fixed height prism base to place prisms at control points B and C to observe the horizontal angles and vertical angles of control points B, C, and all selected pier top feature points; S4: After setting up the total station at control point B, prisms are placed on control points A and C using fixed-height prism bases to observe the horizontal and vertical angles of control points A, C, and all selected pier top feature points; if two total stations are used for synchronous measurement, steps S2-S3 can be performed simultaneously; the height difference of the fixed-height prism bases at control points A, B, and C is less than 0.1 mm, and prisms of the same model and specification are used; if the heights are inconsistent, the heights of each prism need to be accurately recorded; points A and B can use forced centering devices according to actual conditions; S5: solving the plane and elevation of feature points; S51, using the horizontal angles of the control point A, the control point B and the characteristic point, and the plane coordinates of the control point A and the control point B, the plane coordinates of the bridge characteristic point are calculated according to the principle of forward intersection; S52, and reversely calculate the horizontal distances from the control point A and the control point B to each feature point; S53, using the vertical angles and distances from control point A and control point B to point C, as well as the vertical angles and horizontal distances from control point A and control point B to the feature point, measuring the prism height may introduce errors and affect the measurement efficiency due to factors such as uneven ground on site and operator operation errors, and adopt a trigonometric height measurement method without measuring the prism to obtain the elevation of each feature point; S6: Before collecting the pier top image or 3D point cloud in the field, an artificial elevation scale control mark is placed on the pier top by using a drone. Then, when collecting the pier top image or 3D point cloud in the field, the artificial elevation scale control mark exists in the pier top image or 3D point cloud. The artificial elevation scale control mark is a columnar object with a certain height (generally a rectangular block is selected), and the target height needs to be accurately measured in advance. The top of the artificial elevation scale control mark is a plane, and the top plane is rectangular or circular, and its size is determined according to the flight altitude when the image is acquired. A checkerboard or other geometric patterns are printed on the top plane. After the field image or 3D point cloud collection is completed, the artificial elevation scale control mark is transported back to the ground by a drone for reuse, or it can be directly placed on the pier top and not transported back. S7: The plane and elevation coordinates of the selected feature points are obtained. During the three-dimensional model establishment process, plane position and plane scale control, as well as elevation control, are provided. The pier top mark can provide scale control in the elevation direction, thereby meeting the field control requirements for the establishment of the three-dimensional model of the pier top.

[0024] In the present invention, a ground control method for establishing a three-dimensional model of a bridge pier top is adopted by combining ground measurement of pier top feature points and pier top artificial elevation ratio control marks; In the present invention, a total station forward intersection and a trigonometric height measurement method without measuring prism height are combined to construct a complete ground measurement scheme to obtain the three-dimensional coordinates of the pier top feature points.

[0025] In the present invention, an artificial elevation ratio control mark is set up on the pier top by using a drone, thereby ensuring that the vertical ratio of the 3D model of the pier top cannot be unaffected by the pier elevation; The present invention is applicable to various situations such as land piers and underwater piers.

[0026] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A ground control method for accurate modeling of bridge pier tops, characterized in that: Includes steps: S1: Determine two temporary control points A and B on the ground near the bridge pier. The top of the bridge pier top support stone can be seen from the control points A and B. Select four or eight feature points. Two rectangular support stones are set on the bridge pier top. When four feature points are selected, the four feature points are the four top corner points of the rectangle surrounded by the two rectangular support stones. When eight feature points are selected, the eight feature points include the four top corner points of the two rectangular support stones. The distance between the two control points shall not be less than 20m. S2: Select the control point C of the bridge control network near the pier as the known coordinates and measure the plane coordinates of points A and B; S3: After setting up the total station at control point A, use a fixed height prism base to place prisms at control points B and C to observe the horizontal angles and vertical angles of control points B, C, and all selected pier top feature points; S4: After setting up the total station at control point B, use a fixed height prism base to place prisms at control points A and C to observe the horizontal angles and vertical angles of control points A, C, and all selected pier top feature points; if two total stations are used for synchronous measurement, steps S2-S3 can be performed simultaneously; S5: solving the plane and elevation of feature points; S51, using the horizontal angles of the control point A, the control point B and the characteristic point, and the plane coordinates of the control point A and the control point B, the plane coordinates of the bridge characteristic point are calculated according to the principle of forward intersection; S52, and reversely calculate the horizontal distances from the control point A and the control point B to each feature point; S53, using the vertical angles and distances from control point A and control point B to point C, as well as the vertical angles and horizontal distances from control point A and control point B to the feature point, measuring the prism height may introduce errors and affect the measurement efficiency due to factors such as uneven ground on site and operator operation errors, and adopt a trigonometric height measurement method without measuring the prism to obtain the elevation of each feature point; S6: Before collecting the pier top image or 3D point cloud in the field, an artificial elevation scale control mark is placed on the pier top by using a drone. Then, when collecting the pier top image or 3D point cloud in the field, the artificial elevation scale control mark exists in the pier top image or 3D point cloud. S7: The plane and elevation coordinates of the selected feature points are obtained. During the three-dimensional model establishment process, plane position and plane scale control, as well as elevation control, are provided. The pier top mark can provide scale control in the elevation direction, thereby meeting the field control requirements for the establishment of the three-dimensional model of the pier top.

2. A ground control method for accurate modeling of bridge pier tops according to claim 1, characterized in that: In step S2, if there is a lack of construction control points nearby, they are encrypted based on the existing bridge construction control network.

3. The ground control method for accurate modeling of bridge pier top according to claim 1 is characterized in that: In step S4, the difference in height of the prism base at control point A, control point B, and control point C is less than 0.1 mm, and prisms of the same model and specification are used.

4. The ground control method for accurate modeling of bridge pier top according to claim 1 is characterized in that: In step S6, the artificial elevation ratio control mark is a columnar object with a certain height, and the height needs to be accurately measured in advance; the top of the artificial elevation ratio control mark is a plane, and the top plane is a rectangle or a circle; The top flat surface is printed with a checkerboard pattern.

5. The ground control method for accurate modeling of bridge pier top according to claim 1 is characterized in that: In step S6, after the field image or three-dimensional point cloud acquisition operation is completed, the artificial elevation scale control mark is transported back to the ground by a drone for reuse.

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