Baseline iteration adjustment method for tunnel three-dimensional model

Abstract

The invention provides a baseline iteration adjustment method of a tunnel three-dimensional model, and belongs to the technical field of tunnel modeling. The method comprises the steps of obtaining a three-dimensional model of a tunnel through photogrammetry; according to the center line of the tunnel and the section information of the tunnel, the first discrete points in the center line are shifted to the side walls of the tunnel, so that coordinates of the second discrete points on the design lines of the side walls on the two sides of the tunnel are obtained. In the extending direction of the three-dimensional model, a plurality of first feature points are marked at the corresponding hole openings in the three-dimensional model, and a plurality of second feature points are marked in the corresponding hole bodies in the three-dimensional model. And endowing the coordinates of a second discrete point at the portal of the tunnel to the first feature point to obtain the coordinates of a second feature point. And correcting the coordinate of the second feature point through the accumulated chord length of the second feature point in the extension direction of the three-dimensional model. And correcting the coordinates of the second feature point again by calculating the shortest distance from the second feature point to the design line. According to the adjusting method, the precision of tunnel three-dimensional modeling can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel modeling, in particular to a baseline iterative adjustment method of a tunnel three-dimensional model. BACKGROUND

[0002] With the development of modern transportation infrastructure, tunnels play a crucial role in connecting different geographical regions in highway, railway and urban rail transit construction. In order to ensure the safety, stability and functionality of these tunnels, accurate three-dimensional modeling and real-time monitoring become particularly important. Traditional tunnel measurement methods mainly rely on manual measurement and two-dimensional drawings, which not only have low efficiency, but also are difficult to provide sufficient accuracy to meet the increasingly complex engineering requirements.

[0003] In recent years, photogrammetry technology as an efficient, non-contact three-dimensional data acquisition method has been widely used in tunnel detection and modeling. By using high-resolution cameras to take pictures inside the tunnel and using computer vision algorithms to reconstruct the three-dimensional model of the tunnel, not only can greatly improve the work efficiency, but also can reduce the labor cost while ensuring the accuracy of the data. However, due to various factors in actual operation (such as light changes, camera position estimation errors, etc.), the three-dimensional model obtained directly often has certain deviations, which needs further correction and optimization. SUMMARY

[0004] The present application provides a baseline iterative adjustment method of a tunnel three-dimensional model, which aims to improve the accuracy of tunnel three-dimensional modeling.

[0005] In order to achieve the above purpose, the present application provides a baseline iterative adjustment method of a tunnel three-dimensional model, comprising:

[0006] acquiring a three-dimensional model of the tunnel by photogrammetry;

[0007] According to the center line of the tunnel and the cross-sectional information of the tunnel, offsetting a plurality of first discrete points in the center line to the side walls of the tunnel to obtain the coordinates of a plurality of second discrete points on the design line of the side walls on both sides of the tunnel;

[0008] Marking a plurality of first feature points at the corresponding entrance of the three-dimensional model along the extension direction of the three-dimensional model, and marking a plurality of second feature points inside the corresponding tunnel body of the three-dimensional model;

[0009] assigning the coordinates of the second discrete points located at the entrance of the tunnel to the first feature points to obtain the coordinates of the second feature points;

[0010] correcting the coordinates of the second feature points by the cumulative chord length of the second feature points in the extension direction of the three-dimensional model;

[0011] The coordinates of the second feature points are corrected multiple times by calculating the shortest distance of the second feature points to the design line to complete the adjustment of the baseline of the three-dimensional model.

[0012] In an embodiment, according to the center line of the tunnel and the cross-sectional information of the tunnel, multiple first discrete points in the center line are offset to the sidewall of the tunnel, comprising:

[0013] The normal vector of the first discrete point is calculated.

[0014] According to the cross-sectional information of the tunnel, the first discrete point is offset to the design line along the direction of the normal vector corresponding to the first discrete point to obtain the coordinates of the second discrete point.

[0015] In an embodiment, the normal vector of the first discrete point is calculated, comprising:

[0016] Multiple first discrete points are fitted by a cubic spline curve.

[0017] The tangent vector corresponding to multiple first discrete points is obtained.

[0018] In an embodiment, multiple first discrete points are fitted by a cubic spline curve, comprising:

[0019] Multiple first discrete points are fitted by a cubic spline curve in three mutually perpendicular directions, and the formula of the cubic spline curve in each direction is:

[0020]

[0021] In the formula, a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z are all piecewise cubic polynomials, , and are all piecewise cubic polynomials, is the cumulative chord length corresponding to the first discrete point.

[0022] In an embodiment, multiple first discrete points are fitted by a cubic spline curve, comprising:

[0023] A regularization term is introduced into the cubic spline curve corresponding to the first discrete point.

[0024] In an embodiment, the coordinates of the second feature points are corrected by the cumulative chord length of the second feature points in the extension direction of the three-dimensional model, comprising:

[0025] A proportion parameter in the interval [0, 1] is calculated by the cumulative chord length corresponding to the coordinates of the second feature points.

[0026] Interpolating the second feature point on the design line through the ratio parameter to correct the coordinate of the second feature point.

[0027] In an embodiment, the coordinate of the second feature point is corrected again by calculating the shortest distance from the second feature point to the design line, comprising:

[0028] The shortest distance from the second feature point to the design line is obtained by traversing the distance from the second feature point to each of the second discrete points;

[0029] The coordinate of the second discrete point with the shortest distance from the second feature point is assigned to the second feature point to correct the coordinate of the second feature point again.

[0030] In an embodiment, the coordinate of the second feature point is corrected again by calculating the shortest distance from the second feature point to the design line, comprising:

[0031] The design line is constructed by fitting a cubic spline curve to a plurality of the second discrete points;

[0032] The shortest distance from the second feature point to the design line is calculated by numerical extremum optimization;

[0033] The coordinate of the point on the design line with the shortest distance from the second feature point is assigned to the second feature point to correct the coordinate of the second feature point again.

[0034] In an embodiment, a plurality of first feature points are marked at corresponding openings in the three-dimensional model along the extension direction of the three-dimensional model, and a plurality of second feature points are marked inside corresponding openings in the three-dimensional model, comprising:

[0035] The plurality of first feature points are marked at the corner lines of the walls on both sides of the three-dimensional model at the openings, and the plurality of second feature points are marked at the corner lines of the walls on both sides of the three-dimensional model inside the openings.

[0036] The above scheme of the present application has the following advantages:

[0037] In the embodiments of the present application, the first discrete points in the center line are offset to the sidewall of the tunnel to obtain the accurate coordinates of the plurality of second discrete points on the sidewall, with reference to the known center line of the tunnel. In the three-dimensional model of the tunnel, a plurality of first feature points are marked on the sidewall at the portal, and a plurality of second feature points are marked on the sidewall in the tunnel body. The coordinates of the second discrete points on the sidewall at the portal are assigned to the first feature points, so that the three-dimensional model has approximate size information. The second feature points can be uniformly arranged along the extension direction of the three-dimensional model, so that the second feature points have preliminary coordinates. The coordinates of the plurality of second feature points are corrected for the first time through the cumulative distance of the plurality of second feature points in the extension direction of the three-dimensional model, and the coordinates of the second feature points are obtained more accurately according to the shortest distance from the second feature points to the design line. The method of the present application combines photogrammetry technology, and gradually approaches the design line through progressive iterative adjustment of the second feature points, so that the accuracy of the three-dimensional model of the tunnel is higher. Compared with related technologies, the method of the present application can more accurately reflect the actual geometric shape of the tunnel, and reduce the size error and positioning deviation. Furthermore, the first feature points and the second feature points of the present application are automatically obtained and marked based on photogrammetry technology, reducing the need for human intervention, improving work efficiency, and reducing the possibility of errors caused by human factors. Through accurate iterative adjustment of the three-dimensional model of the tunnel, the tunnel can enter the operation and maintenance stage more quickly after construction is completed, and provide more accurate data support for subsequent periodic inspection and maintenance, which helps to discover and solve potential problems in time, and prolongs the service life of the tunnel. The accurate three-dimensional model can also help engineers better understand the tunnel structure, identify potential risk points in advance, and take effective preventive measures to improve the safety of tunnel operation. In addition to being applied to tunnel construction, the method of the present application can also be extended to three-dimensional modeling requirements in other similar underground spaces or complex environments, such as subway stations and underground parking lots, and has a wide application prospect.

[0038] Other benefits of the present application will be described in detail in the subsequent specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 A flowchart of a baseline iterative adjustment method for a three-dimensional model of a tunnel in an embodiment of the present application;

[0040] Figure 2 A distribution diagram of first feature points and second feature points in a three-dimensional model of a tunnel in an embodiment of the present application;

[0041] Figure 3 A schematic diagram of the iterative adjustment process of the second feature points in an embodiment of the present application;

[0042] Figure 4Error convergence curve diagram of the second feature point iterative adjustment in an embodiment of the present application. DETAILED DESCRIPTION

[0043] In order to make the technical problems solved by the present application, the technical solutions and advantages clearer, the following will be described in detail with reference to the drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application. In addition, the technical features involved in the different implementation manners of the present application described below can be combined with each other as long as there is no conflict.

[0044] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0045] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood in a broad sense, for example, it can be a locking connection, or 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 a communication inside two elements. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0046] The embodiments of the present application provide a baseline iterative adjustment method for a tunnel three-dimensional model, aiming at the size error and positioning deviation of the tunnel three-dimensional model directly obtained by photogrammetry technology. The adjustment method of the present application firstly performs preliminary spatial redirection by using first feature points at the entrance and exit of the tunnel, then further refines the model according to second feature points set inside the tunnel, and finally performs iterative adjustment of the shortest distance for multiple times, so that the line shape of the tunnel three-dimensional model is highly consistent with the design line shape. The entire process combines the first and second feature points, camera parameter optimization, and cubic spline curve fitting and interpolation, etc., to ensure the high precision and reliability of the final three-dimensional model. Therefore, the present application provides a new solution for the rapid construction and accurate positioning of the tunnel three-dimensional model by integrating photogrammetry technology and mathematical modeling method. This not only helps to improve the design quality and construction efficiency of the tunnel project, but also provides strong technical support for subsequent operation and management.

[0047] Specifically, referring to Figure 1 The baseline iterative adjustment method for the tunnel three-dimensional model of the present application comprises:

[0048] Step S1: obtaining a three-dimensional model of a tunnel by photogrammetry.

[0049] Illustratively, the three-dimensional model obtained by photogrammetry inside the tunnel has low size and positioning accuracy due to poor positioning signals inside the tunnel, or even no positioning signals, which results in lower accuracy of photogrammetry inside the tunnel than that of photogrammetry on the ground.

[0050] Step S2: offsetting a plurality of first discrete points in the center line to the side walls of the tunnel to obtain coordinates of a plurality of second discrete points on the design lines of the side walls of the tunnel according to the center line of the tunnel and the cross-sectional information of the tunnel.

[0051] Illustratively, the center line of the tunnel contains important line shape data of the plan position information and the longitudinal section elevation information of the tunnel, and the center line of the tunnel is usually discretized into a spatially uniform discrete point sequence represented by ten-meter stakes or hundred-meter stakes. Combined with the design drawing of the tunnel contour cross section, the coordinates of the second discrete points on the design lines of the side walls of the tunnel can be obtained by offsetting the plurality of first discrete points of the center line to the side walls of the tunnel, i.e. calculating the coordinates of the second discrete points from the coordinates of the first discrete points.

[0052] Step S3, referring to Figure 2 Marking a plurality of first feature points at the corresponding openings in the three-dimensional model and a plurality of second feature points inside the corresponding tunnel body in the three-dimensional model along the extension direction of the three-dimensional model.

[0053] Exemplarily, a plurality of first feature points can be marked on the side walls in the three-dimensional model of the tunnel at the portal positions. For example, four first feature points are marked on the side walls at both the entrance and the exit of the three-dimensional model. A plurality of second feature points can be marked on the side walls in the three-dimensional model of the tunnel at the positions within the tunnel body. For example, twelve second feature points are uniformly marked on the side walls at both sides of the three-dimensional model along the extension direction of the three-dimensional model.

[0054] In step S4, the coordinates of the second discrete points located at the portal of the tunnel are assigned to the first feature points to obtain the coordinates of the second feature points.

[0055] Exemplarily, the second discrete points are calculated from the known first discrete points, so that the coordinates of the second discrete points are known accurate position parameters. The coordinates of the second discrete points located at the portal of the tunnel are assigned to the first feature points, so that the coordinates of the first feature points are also known accurate position parameters. Then, the entrance and the exit of the three-dimensional model of the tunnel are adjusted to the correct positions. According to the line type of the design line, the size information of the three-dimensional model can be roughly obtained to preliminarily obtain the coordinates of the second feature points, that is, the three-dimensional space redirection of the three-dimensional model of the tunnel is roughly completed, and the three-dimensional model is also assigned with approximate size information.

[0056] In step S5, please refer to Figure 3 , the coordinates of the second feature points are corrected by the cumulative chord length of the second feature points in the extension direction of the three-dimensional model.

[0057] Exemplarily, the second feature points within the three-dimensional model of the tunnel can be marked at intervals of 50m-100m according to the actual length of the tunnel, and the second feature points are uniformly arranged along the extension direction of the three-dimensional model. By obtaining the cumulative chord length of the plurality of second feature points in the extension direction of the three-dimensional model, the coordinates of the second feature points are corrected for the first time according to the proportional relationship of the cumulative chord lengths of the second feature points and according to the line type of the design line, so that the extension direction of the three-dimensional model roughly conforms to the extension direction of the design line.

[0058] In step S6, please refer to Figure 3 and Figure 4 , the coordinates of the second feature points are iteratively corrected multiple times by calculating the shortest distance from the second feature points to the design line multiple times to complete the adjustment of the baseline of the three-dimensional model.

[0059] Exemplarily, the second feature points after the first correction are gradually iteratively approximated to the design line at the shortest distance. In this process, the coordinates of the second feature points are continuously adjusted so that the line type of the curve formed by the plurality of second feature points matches the line type of the design line, and the accuracy of the corrected three-dimensional model is higher.

[0060] It should be noted that the line type of the curve formed by the plurality of first feature points and the plurality of second feature points can represent the baseline of the three-dimensional model, the coordinates of the first feature points are assigned by the corresponding second discrete points, so that the baseline of the three-dimensional model is preliminarily adjusted, and when the coordinates of the second feature points are iteratively approximated to the design line for multiple times, the coordinates of the second feature points are relatively accurate, so that the baseline of the three-dimensional model is adjusted more accurately, and the three-dimensional model of the tunnel can more truly reflect the actual positioning and size of the tunnel.

[0061] In the embodiment of the application, the first discrete points in the known tunnel center line are offset to the side wall of the tunnel to obtain the accurate coordinates of the plurality of second discrete points on the side wall. In the three-dimensional model of the tunnel, a plurality of first feature points are marked on the side wall at the portal, and a plurality of second feature points are marked on the side wall in the tunnel body. The coordinates of the second discrete points on the side wall at the portal are assigned to the first feature points, so that the three-dimensional model has approximate size information. The second feature points can be uniformly arranged along the extension direction of the three-dimensional model, so that the second feature points have preliminary coordinates. The coordinates of the plurality of second feature points are corrected for the first time through the cumulative distance of the plurality of second feature points in the extension direction of the three-dimensional model, and the more accurate coordinates of the second feature points are obtained according to the shortest distance from the second feature points to the design line. The method of the application combines photogrammetry technology, and gradually iteratively adjusts the second feature points to approach the design line, so that the accuracy of the three-dimensional model of the tunnel is higher. Compared with related technologies, the method of the application can more accurately reflect the actual geometric shape of the tunnel, reduce size errors and positioning deviations. Furthermore, the first feature points and the second feature points of the application are automatically obtained and marked based on photogrammetry technology, reducing the need for human intervention, improving work efficiency, and reducing the possibility of errors caused by human factors. Through accurate iterative adjustment of the three-dimensional model of the tunnel, the tunnel can enter the operation and maintenance stage more quickly after construction is completed, and more accurate data support is provided for subsequent periodic inspection and maintenance, which helps to timely discover and solve potential problems and prolong the service life of the tunnel. The accurate three-dimensional model can also help engineers better understand the tunnel structure, identify potential risk points in advance, and take effective preventive measures to improve the safety of tunnel operation. In addition to being applied to tunnel construction, the method of the application can also be extended to three-dimensional modeling needs in other similar underground spaces or complex environments, such as subway stations and underground parking lots, and has a wide application prospect.

[0062] In an embodiment, according to the center line of the tunnel and the cross-sectional information of the tunnel, the plurality of first discrete points in the center line are offset to the side wall of the tunnel, including:

[0063] The normal vector of the first discrete point is calculated to obtain the direction of the offset of the first discrete point to the design line.

[0064] According to the section information of the tunnel, the first discrete point is offset to the design line along the direction of the normal vector corresponding to the first discrete point to obtain the coordinate of the second discrete point, so that the coordinate of the second discrete point is more accurate.

[0065] In an embodiment, the normal vector of the first discrete point is calculated, including:

[0066] The plurality of first discrete points are fitted by a cubic spline curve.

[0067] The tangent vector corresponding to the plurality of first discrete points is obtained.

[0068] It should be noted that since a screen needs to be defined to determine the direction of the offset of the first discrete point, it is not intuitive to directly calculate the normal vector of the first discrete point, and therefore the tangent vector of the first discrete point can be calculated to calculate the normal vector of the first discrete point. For example, the Fleiner formula is used for calculation, which provides a local coordinate system for each first discrete point, including the tangent, normal and binormal vectors of each first discrete point. In order to simplify the problem, it can be assumed that the given first discrete points are dense enough, and the tangent direction can be approximated by the difference between adjacent points. For the first discrete points located on the inside, central difference can be used, and for the first discrete points located on both sides, forward or backward difference can be used.

[0069] In the embodiments of the present application, before the tangent vector of the first discrete point is calculated, the plurality of first discrete points are fitted by a cubic spline curve to obtain a smooth parameterized curve, which helps to more accurately calculate the tangent vector of each first discrete point and improves the calculation accuracy.

[0070] In an embodiment, the plurality of first discrete points are fitted by a cubic spline curve, including:

[0071] The plurality of first discrete points are fitted by a cubic spline curve in three mutually perpendicular directions to ensure that the fitting in each direction is independent of each other, avoiding the problem of dimension mismatch. At the same time, the cumulative chord length of the first discrete points is used as the parameter of the spline curve fitting in each direction to ensure that the spline fitting is more smooth and uniform. In addition, the derivative of the spline (the tangent vector of the discrete point) is evaluated directly at the parameter of the first discrete point to ensure that the offset is applied at the position of the first discrete point. The formula of the cubic spline curve fitting in each direction is:

[0072]

[0073] In the formula, , and are piecewise cubic polynomials, is the cumulative chord length corresponding to the first discrete point.

[0074] Exemplarily, in three-dimensional space, the fitting of cubic spline curves can be extended to handle three-dimensional point sets , , ). Among them, =0,1,… . Each coordinate component , , can be represented by a cubic spline function respectively, and a parameter is introduced to define the parametric form of the curve. Assuming that the parameter is a monotonically increasing variable, the parameter can be usually selected as the cumulative chord length at the nodes or other custom distribution. For a given data point , , and the corresponding parameter , cubic spline functions can be used to fit , and respectively.

[0075] For each component, the form of the cubic spline function on the interval , is:

[0076]

[0077]

[0078]

[0079] In the formula , , , , are coefficients (likewise, in the formula and the formula are also coefficients), is the cumulative chord length corresponding to the first discrete point.

[0080] In order to determine the coefficients , , , (in the formula and corresponding to the coefficients of the component), the following conditions need to be met:

[0081] Interpolation condition: at each node, the curve passes through the given point to meet:

[0082]

[0083] Continuity condition: the first and second derivatives are continuous at the interior nodes, satisfying:

[0084]

[0085]

[0086]

[0087] Parameter is chosen from the following two common schemes:

[0088] Uniform parameterization: let = , i.e., the parameter is uniformly distributed between the nodes.

[0089] Chord length parameterization: let be the cumulative chord length, i.e.,

[0090]

[0091] In an embodiment, the plurality of first discrete points are fitted with a cubic spline curve, comprising:

[0092] A regularization term is introduced in the cubic spline curve corresponding to the first discrete points. Cubic spline fitting is different from interpolation, which does not require the curve to pass through all data points strictly, but approximates the data points by minimizing the error. For the fitting problem, the smoothness of the curve can be controlled by introducing a regularization term.

[0093] For example, it is assumed that the goal is to minimize the following objective function:

[0094]

[0095] In the formula, the first term is the fitting error of the data points, the second term is the smoothness constraint, which is used to punish the case of excessive curvature, > 0, is a regularization parameter, which is used to balance the fitting accuracy and smoothness.

[0096] By optimizing the above objective function, the fitted cubic spline curve can be obtained.

[0097] It should be noted that the adjustment of the three-dimensional model using the cubic spline curve can flexibly adjust the smoothness and accuracy of the three-dimensional model according to actual needs. Whether it is for a newly built tunnel or the maintenance and reconstruction of an existing tunnel, this method shows good adaptability.

[0098] In an embodiment, the coordinates of the second feature point are corrected by the cumulative chord length of the second feature point in the extension direction of the three-dimensional model, including:

[0099] A proportional parameter in the interval [0, 1] is calculated by the cumulative chord length corresponding to the coordinates of the second feature point.

[0100] The coordinates of the second feature point are corrected by interpolation of the proportional parameter on the design line to approximate the second feature point to the design line.

[0101] Exemplarily, similar to the process of cubic spline curve fitting of the first discrete points, a proportional parameter in the interval [0, 1] is calculated by the cumulative chord length of the current coordinates of the second feature point, and the converted proportional parameter is used as the parameter of cubic spline curve interpolation, and finally the coordinates of the second feature point are corrected by the obtained parameterized equation to ensure the accuracy of the three-dimensional model and speed up the data processing speed, which is of great significance for the rapid implementation of large-scale engineering projects.

[0102] In an embodiment, the coordinates of the second feature point are corrected again by calculating the shortest distance from the second feature point to the design line, including:

[0103] The shortest distance from the second feature point to the design line is obtained by traversing the distance from the second feature point to each second discrete point;

[0104] The coordinates of the second discrete point with the shortest distance from the second feature point are assigned to the second feature point to correct the coordinates of the second feature point again.

[0105] In the embodiments of the present application, for the design line composed of relatively dense second discrete points, the shortest distance corresponding point can be found by simply traversing the distance from the second feature point to all second discrete points on the design line, so that the calculation is relatively simple.

[0106] In an embodiment, the coordinates of the second feature point are corrected again by calculating the shortest distance from the second feature point to the design line, including:

[0107] The multiple second discrete points are fitted by cubic spline curve to construct the design line;

[0108] The shortest distance from the second feature point to the design line is calculated by numerical extremum optimization;

[0109] The coordinates of the point on the design line with the shortest distance from the second feature point are assigned to the second feature point to correct the coordinates of the second feature point again.

[0110] In the embodiments of the present application, the second discrete points are fitted by cubic spline curve to further improve the calculation accuracy.

[0111] Exemplarily, a distance function , the independent variable of the function is the parameter of the spline curve , the dependent variable is the square of the distance from the second feature point to any point on the spline curve. Therefore, the parameter value corresponding to the minimum square of the distance can be found in the interval [0, 1] , and the coordinates of the corrected second feature point are calculated through the spline curve parameterization equation.

[0112] In an embodiment, a plurality of first feature points are marked at the corresponding opening of the three-dimensional model along the extension direction of the three-dimensional model, and a plurality of second feature points are marked in the corresponding opening of the three-dimensional model, comprising:

[0113] A plurality of first feature points are marked at the corner lines of the side walls of the three-dimensional model at the opening, and a plurality of second feature points are marked at the corner lines of the side walls of the three-dimensional model in the opening.

[0114] It should be noted that the corner lines of the side walls of the tunnel are usually geometric turning points on the cross section of the tunnel profile, and the features are relatively clear. In addition, the points near the corner lines generally contain key information such as milepost numbers required for tunnel operation and maintenance, and are relatively ideal linear control points, so the first feature points and the second feature points can be taken from the corner lines of the side walls of the three-dimensional model to improve the accuracy of the calculation.

[0115] The above is the preferred embodiment of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. A method for baseline iterative adjustment of a tunnel three-dimensional model, characterized in that, The method comprises the following steps: obtaining a three-dimensional model of the tunnel through photogrammetry; offsetting a plurality of first discrete points in the center line to the side walls of the tunnel according to the center line of the tunnel and the cross-sectional information of the tunnel to obtain the coordinates of a plurality of second discrete points on the design line of the side walls on both sides of the tunnel; marking a plurality of first feature points at the corresponding openings in the extension direction of the three-dimensional model and a plurality of second feature points in the corresponding tunnel body in the three-dimensional model; assigning the coordinates of the second discrete points at the openings of the tunnel to the first feature points to obtain the coordinates of the second feature points; correcting the coordinates of the second feature points through the cumulative chord length of the second feature points in the extension direction of the three-dimensional model; correcting the coordinates of the second feature points through multiple iterations by calculating the shortest distance of the second feature points to the design line to complete the adjustment of the baseline of the three-dimensional model.

2. The method of claim 1, wherein, The method comprises the following steps: calculating the normal vector of the first discrete point; offsetting the first discrete point to the design line along the corresponding normal vector of the first discrete point according to the cross-sectional information of the tunnel to obtain the coordinates of the second discrete point.

3. The method of claim 2, wherein, The method comprises the following steps: performing cubic spline curve fitting on a plurality of first discrete points; obtaining the tangent vector corresponding to a plurality of first discrete points.

4. The method of claim 3, wherein, The method comprises the following steps: performing cubic spline curve fitting on a plurality of first discrete points in three mutually perpendicular directions, and the formula of the cubic spline curve fitting in each direction is: wherein , and are piecewise cubic polynomials, is the cumulative chord length corresponding to the first discrete point.

5. The method for baseline iterative adjustment of a tunnel 3D model according to claim 3, wherein, The method comprises the following steps: introducing a regularization term in the cubic spline curve corresponding to the first discrete point.

6. The method for baseline iterative adjustment of a tunnel 3D model according to claim 1, wherein, The method comprises the following steps: calculating a proportion parameter in the interval [0, 1] through the cumulative chord length corresponding to the coordinates of the second feature point; correcting the coordinates of the second feature point by interpolation on the design line through the proportion parameter.

7. The method for baseline iterative adjustment of a tunnel 3D model according to claim 1, wherein, The method comprises the following steps: obtaining the shortest distance of the second feature point to the design line by traversing the distance of the second feature point to each second discrete point; assigning the coordinates of the second discrete point with the shortest distance to the second feature point to the second feature point to correct the coordinates of the second feature point again.

8. The method for baseline iterative adjustment of a tunnel 3D model according to claim 1, wherein, The method comprises the following steps: performing cubic spline curve fitting on a plurality of second discrete points to construct the design line; calculating the shortest distance of the second feature point to the design line through numerical extreme value optimization; Assign the coordinates of the point with the shortest distance between the design line and the second feature point to the second feature point to correct the coordinates of the second feature point again.

9. The method for baseline iterative adjustment of a tunnel 3D model according to claim 1, wherein, Mark a plurality of first feature points at corresponding openings in the three-dimensional model and a plurality of second feature points inside corresponding openings in the three-dimensional model along the extension direction of the three-dimensional model, including: Mark a plurality of the first feature points at the corner lines of the walls on both sides of the three-dimensional model at the openings and mark a plurality of the second feature points at the corner lines of the walls on both sides of the three-dimensional model inside the openings. Mark a plurality of the first feature points at the corner lines of the walls on both sides of the three-dimensional model at the openings and mark a plurality of the second feature points at the corner lines of the walls on both sides of the three-dimensional model inside the openings.

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