A method for measuring and setting the road surface elevation at a plant road intersection

Abstract

A kind of method for measuring and setting road surface elevation at plant road intersection, steps include: the road surface construction area at intersection is divided into several construction subareas;Determine several known elevation points in construction subarea range and enter computer;Establish digital terrain model of each construction subarea based on known elevation points;Draw contour line of construction subarea with the elevation of known elevation points as constraint condition;Select several points as road surface construction elevation control points along the contour line of construction subarea, and obtain its three-dimensional coordinates;Using measuring instrument, each control point is measured and placed to construction site and marked to complete surface elevation.The application adopts the inverted method of drawing contour line from known point and then taking point along contour line to define surface, which realizes smooth transition of road surface elevation difference and smooth butt joint with surrounding road surface while ensuring the correct elevation of each known point, with high measuring and setting precision and efficiency.

Description

Technical Field

[0001] This application belongs to the field of engineering surveying technology, specifically relating to a method for measuring the road surface elevation at the intersection of factory roads, and more particularly to a method for determining and setting out the road surface construction elevation control points in intersection areas where multiple roads intersect and the road surface elevation changes non-linearly. Background Technology

[0002] Construction work on factory roads often involves the construction of road intersections. Intersections can be categorized by their at-grade intersection form, such as T-junctions, crossroads, and angled intersections (e.g., passing lanes). Sometimes, more complex intersections may also be encountered. For example... Figure 1 In the example shown, the intersection connects to a road on each of the east, west, and north sides, and then connects to a plane at the south side of the factory gate before connecting to the external municipal road. The design only provides the plane location and the road width, longitudinal slope, transverse slope, and elevation of each plane area.

[0003] The road surface construction elevation in this intersection area is subject to multiple constraints and combined influences from the road surface in various directions, exhibiting a non-linear changing trend. Therefore, a reasonable construction elevation cannot be obtained using general slope calculation methods. Specifically, the road surface elevation in the intersection area is usually affected by multiple constraints such as the transverse slope and longitudinal slope of other road surfaces connected to it, making the road surface elevation in this area exceptionally complex and non-linear, which is difficult to describe using a unified slope formula.

[0004] In actual construction, due to limitations in construction technology and traditional practices, many problems are solved by methods commonly known as "following the slope," such as "relying on visual inspection and using string lines." Predictably, this experience-based approach ultimately leads to unsatisfactory construction results, causing quality defects such as "twisted, uneven, and rough" road surfaces, poor drainage at intersections, driving discomfort, high rework rates, and severely impacting the construction quality and functionality of factory roads.

[0005] In the existing technology, although computer mapping software, satellite positioning measurement instruments (such as GPS-RTK), total stations and other hardware and software equipment are widely used in the field of engineering surveying, there is still a lack of a systematic surveying method for road surface elevations with multiple constraints and nonlinear changes, such as intersections. This method can ensure the accuracy of the values ​​of each known control elevation point, achieve a smooth transition of elevation differences between points, and smoothly connect with the road surfaces of surrounding roads.

[0006] Therefore, it is urgent to find a reasonable surveying method to fundamentally solve the technical problems of difficulty in determining the road surface construction elevation and poor construction results in intersection areas. Summary of the Invention

[0007] To address the aforementioned shortcomings of existing technologies, this application provides a method for measuring the road surface elevation at intersections in factory areas. By rationally dividing the construction area at the intersection into zones, a digital ground model is established using known elevation points in each zone as constraints, and contour lines are drawn. Then, road construction elevation control points are selected along the contour lines. Finally, measuring instruments are used to project each control point onto the actual construction site. This method ensures the accuracy of the known elevation point values ​​while achieving a smooth transition of the road surface elevation at the intersection and a smooth connection with the surrounding road surface. It solves the technical problems of nonlinear road surface elevation at intersections being undetermined using conventional slope methods and the traditional "slope-following" method leading to uneven and distorted road surfaces, significantly improving the construction quality and measurement efficiency of the road surface at the intersection.

[0008] A method for measuring the road surface elevation at an intersection in a factory area, wherein the intersection is a region where multiple roads intersect and the road surface elevation changes non-linearly, the steps include:

[0009] S1. Divide the road construction area at the intersection into several construction zones;

[0010] S2. For each construction zone, determine several known elevation points within its range. The known elevation points include at least one of the elevation points directly given by the design, the elevation points calculated based on the design values ​​of the surrounding roads, and the elevation points obtained by on-site measurement. The plane position and corresponding elevation of each of the known elevation points are entered into the computer.

[0011] S3. Based on the known elevation points of the construction zones, establish a digital ground model for each construction zone;

[0012] S4. Based on the digital ground model, and using the elevation of the known elevation points as constraints, draw the contour lines of the construction zone;

[0013] S5. Select several elevation points along the contour lines of the construction zone, and use each selected elevation point as the road construction elevation control point of the construction zone, and obtain the three-dimensional coordinates of each road construction elevation control point.

[0014] S6. Using measuring instruments, the three-dimensional coordinates of each of the road construction elevation control points are measured and laid out to the actual construction site, and the finished road surface elevation is marked at the corresponding location on the actual site.

[0015] Furthermore, in S1, according to construction needs, the local area at the intersection where a flat road surface or drainage system needs to be set up is separately divided into a construction zone.

[0016] Furthermore, in step S2, each of the known elevation points is added to the plan view of the construction zone, and an elevation point data file containing the three-dimensional coordinates of each of the known elevation points is generated simultaneously.

[0017] Furthermore, in step S3, the triangular network data file of the construction zone is generated and saved simultaneously during the process of establishing the digital ground model.

[0018] Furthermore, in step S4, the contour lines are calculated and drawn using cubic B-spline curve fitting.

[0019] Furthermore, in S4, the contour interval of the contour lines is determined based on the area of ​​the construction zone and the maximum elevation difference of the slope.

[0020] Furthermore, in step S5, elevation points are selected uniformly along the contour lines, and the density of each selected elevation point is approximately one point every 3 meters, arranged in a quincunx pattern.

[0021] Furthermore, in step S5, the selected elevation points are used as the road construction elevation control points, and the three-dimensional coordinates of the road construction elevation control points are saved as a road control point data file.

[0022] Furthermore, in S6, when the construction structure layer is a roadbed, the triangulation network data file is imported into a satellite positioning measuring instrument, and the surface layout method is used for surveying and layout; when the construction structure layer is a concrete pavement layer, the pavement control point data file is imported into a total station, and the three-dimensional coordinate point layout method is used for surveying and layout.

[0023] Furthermore, the total station is used to set up the three-dimensional coordinate points using the instrumentless elevation method.

[0024] This application proposes a method for measuring the road surface elevation at intersections in factory areas. By using digital modeling and reverse contour line sampling, it abandons the traditional "slope-following" experience and generates a smooth and continuous surface with known elevation points as constraints. This ensures that the road surface at the intersection smoothly connects with the surrounding roads and avoids quality defects such as distortion and unevenness. At the same time, it combines cubic B-spline fitting to improve adaptability to complex terrain. GPS-RTK surface layout and total station point layout are used for the roadbed and concrete surface layer respectively, balancing efficiency and accuracy. The method is simple and reliable to operate. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the road intersection area partitions and their known elevation points in the embodiments of this application;

[0026] Figure 2 This is a schematic diagram illustrating the principle of surveying and setting the road surface elevation in the construction area at the intersection, as described in this application.

[0027] In the diagram: 1. Centerline; 2. Edge line; 3. Elevation point; 3′, Design-given elevation point; 4. Longitudinal slope; 5. Lateral slope; 6. Control point; 7. Contour line. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description, in conjunction with the accompanying drawings and engineering examples, further illustrates this application. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit it; the mapping software, satellite positioning measuring instruments, total stations, etc., mentioned in the embodiments are merely exemplary implementation means, and any computer and measuring instrument capable of achieving the corresponding functions can be applied.

[0029] This embodiment uses Figure 1 , Figure 2 The following example illustrates a factory road intersection. Figure 1 This is a schematic diagram of the road intersection area and its known elevation points. The diagram shows the division of the three construction zones, A, B and C, as well as elements such as centerline 1, edge line 2, known elevation points 3, longitudinal slope 4, transverse slope 5, and contour lines 7. Figure 2 This is a schematic diagram illustrating the principle of road surface construction elevation measurement in the intersection construction area of ​​this application embodiment. The diagram shows contour lines 7 drawn under the constraints of the designed elevation points 3′ (there are 4 in total, which are the locations marked by solid black dots and double concentric circles in the diagram), as well as road surface construction elevation control points 6 selected along the contour lines (the locations marked by double concentric circles in the diagram), and the distribution relationship of known road surface elevation points and elevations. All the locations marked by solid black dots in the diagram are road surface feature points and elevations obtained through calculation; the locations marked by hollow circles and double concentric circles are road surface construction elevation control points and elevations obtained from the contour lines.

[0030] exist Figure 1 In the diagram, the factory area's road intersection connects to three roads on the east, west, and north sides (Road 1, Road 2, and Road 3). On the south side, towards the factory gate, it connects to a level road before linking with an existing municipal road. The design specifies the centerline 1, edge lines 2, road width W, longitudinal slope 4, transverse slope 5, and elevation of the level area for each road. Several known road surface elevation points 3 are marked on the diagram (including design values, estimated values, and measured values, such as 1353.36, 1353.348, 1353.26, 1353.38, 1352.876, 1352.911, 1352.097, 1351.776, and 1351.454), along with the requirement for a level road surface of "1353.0m elevation in the corridor area" at the intersection.

[0031] The principle behind the surveying method proposed in this application is as follows: Road surface elevation at intersections is typically influenced by multiple constraints, such as the transverse and longitudinal slopes of other connected road surfaces, resulting in an exceptionally complex and non-linear elevation profile. Contour lines, as curves representing surface features on a plan view, are drawn based on a set of ground elevation points through fitting calculations. This application, however, uses the known elevation points of the surface to be determined as constraints to draw contour lines. Then, based on the fitted contour lines, points are taken along the lines to inversely calculate the construction elevation control points for the road surface to be determined. This is essentially a "reverse approach" to the conventional process of "fitting elevation points into a surface." This method effectively determines the construction elevation of the road surface at road intersections, and practice has proven its feasibility.

[0032] The principle is explained as follows: Computer mapping software typically uses cubic B-spline curve fitting to calculate contour lines. Before drawing contour lines, a digital terrain model must first be established, which is the set of known elevation points on the road surface obtained through calculation. Figure 1 The three-dimensional triangular network formed by sequentially connecting known road surface elevation points (3) allows for the construction of cubic function segments between adjacent triangular points during cubic B-spline curve fitting. These segments are then interpolated to generate continuous curves. Each curve segment satisfies position, slope, and curvature continuity at the nodes, thus achieving high-precision and smooth contour line drawing, particularly suitable for handling complex local terrain. Therefore, using contour lines to process road surface elevations in intersection areas ensures the accuracy of elevations at known points while achieving a smooth transition between elevation differences. The resulting contour lines form a surface that seamlessly connects with the surrounding road surfaces.

[0033] Furthermore, the points selected along contour lines in this surveying method fall on contour lines with definite elevations. Therefore, the elevation of each selected point is precisely determined by the continuous surface implied by the contour lines. Uniformly and densely selecting points along contour lines is equivalent to discretely sampling this smooth, continuous surface, thus obtaining a set of road construction elevation control points that conform to nonlinear variation laws and have smooth transitions between each other. The more control points and the smaller the contour interval, the more refined and smooth the fitted road surface will be. Using this control point set for on-site layout allows for the accurate reproduction of the smooth, continuous road surface at intersections in the actual field.

[0034] S1. Divide the road construction area at the intersection into several construction zones.

[0035] Import the road surface plan of the construction area at the intersection and other roads connected to it into computer mapping software (such as CASS), adjust the coordinate system and coordinate values ​​of the entire map, and ensure that the coordinates of each point are consistent with the design coordinates.

[0036] Then, based on the actual needs of the site, the intersection construction area is divided into zones. For example... Figure 1As shown, this embodiment is divided into three construction zones: Zone A, Zone B, and Zone C. The purpose of this zoning is that the road surface in the intersection area is constrained by multiple directions, and there may be special elevation requirements in some areas. If the entire area is treated without differentiation, it is difficult to simultaneously address the various local constraints and ensure overall smoothness. In this embodiment, due to the need to install a retractable gate and a gatekeeper's drainage system at the factory entrance, a flat road surface with an elevation of 1353.0m is specifically set up in Zone B. Figure 1 As shown in Zone B, because the flat road surface blocks the continuous slope of the north-south road surface, the entire intersection area must be constructed in sections due to the blockage of Zone B. The local area (Zone B) where the flat road surface or drainage needs to be installed is divided into a separate construction zone, and Zones A and C on both sides of it are further divided into separate zones to ensure that the three road surfaces meet the usage requirements and achieve a smooth transition.

[0037] It should be noted that the number and scope of the zones are not fixed and can be flexibly determined according to the intersection type (T-junction, cross, oblique intersection, etc.), local special elevation requirements (such as setting up a flat road surface, drainage, etc.), and actual construction needs. The zone boundaries should be selected in areas with relatively gentle elevation changes to facilitate a smooth elevation transition between adjacent zones, and are not limited to the three zones in this embodiment.

[0038] S2. For each construction zone, determine several known elevation points within its range, and enter the plane position of each known elevation point and its corresponding elevation into the computer.

[0039] The known elevation points include at least one of the following: elevation points directly given in the design, elevation points calculated based on the design values ​​of surrounding roads, and elevation points obtained through on-site measurements. For example... Figure 1 As shown, for areas A, B, and C, known elevation points 3 are determined within each sub-area. The elevations of these known elevation points 3 come from three sources:

[0040] Firstly, the elevation point 3 directly given by the design—the solid black dot on the design drawings where the elevation value is clearly marked in areas A and B;

[0041] Secondly, the elevation point 3, calculated based on the design values ​​of the surrounding roads—a point whose plane coordinates and elevation are not directly given in the design but can be calculated based on the design values ​​of the centerline 1, edge line 2, longitudinal slope 4, and transverse slope 5 of the surrounding roads. Figure 1 (Represented by hollow circles, distributed in areas A and B).

[0042] Third, the elevation point 3 obtained from on-site measurements—such as the elevation point 3 at the junction of the new road in Zone C and the external municipal road (already completed)—must be obtained from on-site measurements to ensure a smooth connection between the old and new road surfaces.

[0043] The three types of known elevation points mentioned above constitute the most fundamental set of control points for determining the final shape of the road surface in the road intersection area. After the elevation of each point is determined, the "Add General Elevation Points" method in computer mapping software is used to add annotations of each point's location and corresponding elevation onto the plan view. This method not only marks each point on the map but also automatically generates and saves a digital file containing the three-dimensional coordinates of each point (e.g., "Area A Elevation Points.dat"). This completes the entry of the plan view location and elevation of the known elevation points in each zone.

[0044] S3. Based on the known elevation points of the construction zones, establish a digital ground model for each construction zone.

[0045] like Figure 2 As shown, the digital terrain model should be built in zones. Taking zone A as an example: following the prompts of the mapping software, first build a digital terrain model (DTM) based on the above-mentioned known elevation point data file (zone A elevation points.dat), and save the triangular mesh data file automatically generated during the modeling process as "zone A triangular mesh.sjw" for use in the subsequent subgrade structure layer construction using the surface layout method.

[0046] The digital ground model is a three-dimensional triangular network formed by sequentially connecting the known elevation points 3 of the zone. It provides the basis for subsequent contour line drawing, and the saved triangular network data file can also be used for subsequent surface layout of the roadbed structure layer. Similarly, digital ground models are established for zones B and C, and the corresponding triangular network data files are saved.

[0047] S4. Based on the digital ground model, draw contour lines for the construction zone using the known elevation points as constraints.

[0048] After the digital terrain model is built, click the "Draw Contour Lines" function in the mapping software. The computer will automatically draw the contour lines for that area, such as... Figure 2 The intermediate elevation line is shown in Figure 7.

[0049] like Figure 2 As shown, contour line 7 is based on the design elevation point 3′ on the road surface of each zone ( Figure 2 The contour lines are drawn using the elevation of the points marked by solid black dots and double concentric circles as constraints, smoothly and continuously representing the nonlinear undulations of the road surface in that section. Contour lines are typically drawn using cubic B-spline curve fitting calculations: during fitting, a cubic function segment is constructed between two adjacent triangulation points (the elevation point 3′ given in the design on the road surface), and a continuous curve is generated through interpolation. Each curve segment satisfies the continuity of position, slope, and curvature at the nodes, thereby achieving high-precision and smooth contour line drawing, which is particularly suitable for handling locally complex terrain such as intersections.

[0050] The selection of contour intervals depends on the size of the area and the maximum elevation difference of the slope: larger areas with greater elevation differences can have larger contour intervals, while smaller areas requiring more precise contours should have smaller contour intervals. A smaller contour interval results in a more refined and smoother road surface obtained from subsequent point sampling along the route. It should be noted that a smaller contour interval also results in a higher density of control points along the route, leading to a more refined and smoother road surface morphology reconstructed from these control points. In actual construction, the contour interval should be determined comprehensively based on the road surface accuracy requirements and construction costs.

[0051] S5. Select several elevation points along the contour lines of the construction zone, and use each selected elevation point as the road construction elevation control point of the construction zone, and obtain the three-dimensional coordinates of each road construction elevation control point.

[0052] After the contour lines are drawn, select several points along contour line 7. The points should be selected evenly on the primary or secondary contour lines, using the "Add General Elevation Points" method. That is, enter the corresponding command in the mapping software's command line, turn on "Object Snap," and then use the mouse to evenly select elevation points of a certain density along each contour line. Each mouse click automatically generates a point annotation symbol with an elevation value on the map, such as... Figure 2 As shown in control point 6, the software will automatically write the three-dimensional coordinate data of these points into the road control point data file (such as "Area A Road Surface.dat") and save it.

[0053] Since all selected points fall on contour lines 7 with definite elevations, the elevation of each point is precisely determined by the smooth, continuous surface implied by the contour lines. Taking points evenly and densely along the contour lines is equivalent to discretely sampling this smooth, continuous surface. These points are the road construction elevation control points 6.

[0054] As a preferred method, the control point density is approximately one point every 3 meters, arranged in a staggered, quincunx pattern (i.e., adjacent points are evenly distributed to avoid missing local information due to neat rows), to ensure control accuracy while reducing workload. The more control points there are and the more evenly distributed they are, the more refined and smooth the road surface will be. Similarly, control points are selected along their respective contour lines for areas B and C, and their respective road surface control point data files are saved.

[0055] like Figure 2 In the example shown, the road construction elevation control point 6 selected on the contour line has a definite construction control point elevation value (such as 1352.055), while the elevation point 3′ given by the design on the road surface has an original elevation value (such as 1353.000). Together, they constitute the elevation control system of the road surface in this area.

[0056] S6. Using measuring instruments, the three-dimensional coordinates of each of the road construction elevation control points are measured and laid out to the actual construction site, and the finished road surface elevation is marked at the corresponding location on the actual site.

[0057] Taking area A as an example, such as Figure 2 As shown, after obtaining the elevation control points 6 for road construction in each area, the total station or satellite positioning surveying instrument (such as GPS-RTK) can be used for on-site surveying and setting out. The setting-out method can be flexibly selected according to the different structural layers: for subgrade construction with relatively low accuracy requirements, the "surface setting-out" method using a satellite positioning surveying instrument based on triangulation data files can display cut and fill values ​​in real time, making the operation intuitive and quick; for concrete pavement layers with higher accuracy requirements, the "three-dimensional coordinate point setting-out" method using a total station based on pavement control point data files can achieve millimeter-level accuracy. Both methods have their own strengths, balancing efficiency and accuracy.

[0058] When the construction structure layer is the roadbed, since the accuracy requirements for roadbed construction are not high, the "surface layout" function of a satellite positioning surveying instrument based on the aforementioned triangulation data file "Area A Triangulation Network.sjw" can be used for layout. During layout, the triangulation data file "Area A Triangulation Network.sjw" is imported into the handheld device of the satellite positioning surveying instrument. The instrument can display the construction elevation fill and cut values ​​of any point in the area in real time. The operation is user-friendly, intuitive, and simple, effectively improving the layout speed and work efficiency.

[0059] When the construction structure layer is a concrete pavement, the accuracy requirements for concrete pavement construction are high, and the accuracy of satellite positioning surveying instruments cannot meet the construction requirements. Therefore, the "3D coordinate point layout" function of a total station based on the data file "Area A Road Surface.dat" should be used for layout. During layout, first import the pavement control point data file into the total station, and then measure each point in the field in sequence. As a preferred method, the total station can be set up using the "instrumentless elevation method," which can improve its elevation measurement accuracy to the level of ordinary leveling, thereby completing the pavement layout with high precision.

[0060] Regardless of the layout method used, during on-site surveying, the horizontal position of a point should be determined first, and then the corresponding elevation should be measured. This elevation should be marked on the stake with paint or tape; this mark indicates the elevation of each finished surface layer of the road. The same method should be used for surveying and layout in areas B and C.

[0061] Thus, through the complete process of zoning, obtaining known elevation points, establishing a digital ground model, drawing contour lines, taking points along the contour lines, and conducting on-site layered layout, a smooth transition of the road surface elevation in the intersection area and a smooth connection with the surrounding road surface were achieved while ensuring the accuracy of the values ​​of each known elevation point. This ultimately completed the road surface elevation survey of the intersection area. Other types of intersections (T-junctions, oblique intersections, etc.) can be implemented in the same way.

[0062] Compared with the prior art, this application has the following beneficial effects:

[0063] First, this application abandons the traditional experience-based approach of "relying on intuition and using string lines to follow the slope," solving the problem that conventional slope formulas cannot handle nonlinear road surface elevations at intersections. Its core lies in the "inverted construction method"—drawing contour lines using known elevation points as constraints, and then discretely selecting points along the contour lines as construction control points. This ensures the accuracy of the known point elevations and achieves a smooth transition between elevation differences, allowing the road surface at the intersection to smoothly connect with roads in all directions, fundamentally avoiding quality defects such as road surface distortion, unevenness, and roughness.

[0064] Second, contour line drawing uses cubic B-spline curve fitting, which is highly accurate and has continuous curvature, making it particularly suitable for complex terrains with multiple constraints, such as intersections. The more control vertices and the smaller the contour interval, the more refined and smooth the generated road surface will be, and it can be flexibly adjusted according to accuracy requirements.

[0065] Third, this application makes full use of the current mature computer mapping software and measuring instruments to organically link the steps of estimating elevation, establishing a digital ground model, drawing contour lines, taking points along contour lines, and generating control point files, so as to realize the entire process of digital operation, which is simple and efficient and reduces the human error rate.

[0066] Fourth, flexible layout methods are selected for different construction structural layers: for roadbeds with low accuracy requirements, satellite positioning instruments based on triangulation data files are used for "surface layout," with the cut and fill values ​​displayed on the screen in real time, making the operation intuitive and quick; for concrete surface layers with high accuracy requirements, total stations are used for "three-dimensional coordinate point layout," supplemented by instrumentless elevation method, so that the elevation accuracy reaches the level of ordinary leveling, balancing efficiency and accuracy.

[0067] Fifth, by rationally dividing the intersection area, special areas that require flat road surfaces, drainage, etc., can be treated as separate zones, ensuring that each section meets functional requirements and transitions smoothly with each other. This is applicable to various complex intersections such as T-junctions, crossroads, and oblique intersections, and has high engineering promotion value.

[0068] The above description is merely a preferred embodiment of this application. In this application, the number and scope of construction zones can be flexibly determined according to the intersection type and local special elevation requirements; the source of known elevation points is not limited to a combination of design-given, calculated, and measured data, but can be any one or more of these; the contour line fitting method is preferably cubic B-spline curve fitting, but not limited to this; the point density and layout (e.g., one point every 3 meters, quincunx pattern) are preferred and can be adjusted according to accuracy requirements; the mapping software, satellite positioning measuring instruments, total stations, etc., used for on-site layout are all exemplary means, and any computer and measuring instrument capable of performing corresponding digital modeling, contour line drawing, and coordinate layout functions can be applied. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for measuring the road surface elevation at an intersection in a factory area, wherein the intersection is an area where multiple roads intersect and the road surface elevation changes non-linearly, characterized by the following steps: include: S1. Divide the road construction area at the intersection into several construction zones; S2. For each construction zone, determine several known elevation points within its range. The known elevation points include at least one of the elevation points directly given by the design, the elevation points calculated based on the design values ​​of the surrounding roads, and the elevation points obtained by on-site measurement. The plane position and corresponding elevation of each of the known elevation points are entered into the computer. S3. Based on the known elevation points of the construction zones, establish a digital ground model for each construction zone; S4. Based on the digital ground model, and using the elevation of the known elevation points as constraints, draw the contour lines of the construction zone; S5. Select several elevation points along the contour lines of the construction zone, and use each selected elevation point as the road construction elevation control point of the construction zone, and obtain the three-dimensional coordinates of each road construction elevation control point. S6. Using measuring instruments, the three-dimensional coordinates of each of the road construction elevation control points are measured and laid out to the actual construction site, and the finished road surface elevation is marked at the corresponding location on the actual site.

2. The surveying method according to claim 1, characterized in that, In S1, according to construction needs, the local area at the intersection where a flat road surface or drainage system needs to be set up is separately divided into a construction zone.

3. The surveying method according to claim 1, characterized in that, In step S2, each of the known elevation points is added to the plan view of the construction zone, and an elevation point data file containing the three-dimensional coordinates of each of the known elevation points is generated simultaneously.

4. The surveying method according to any one of claims 1-3, characterized in that, In step S3, the triangular network data file of the construction zone is generated and saved simultaneously during the process of establishing the digital ground model.

5. The surveying method according to claim 4, characterized in that, In step S4, the contour lines are calculated and drawn using cubic B-spline curve fitting.

6. The surveying method according to claim 5, characterized in that, In step S4, the contour interval of the contour lines is determined based on the area of ​​the construction zone and the maximum elevation difference of the slope.

7. The surveying method according to claim 6, characterized in that, In step S5, elevation points are selected evenly along the contour lines, and the density of each selected elevation point is approximately one point every 3 meters, arranged in a quincunx pattern.

8. The surveying method according to any one of claims 5-7, characterized in that, In step S5, the selected elevation points are used as the road construction elevation control points, and the three-dimensional coordinates of the road construction elevation control points are saved as a road control point data file.

9. The surveying method according to claim 8, characterized in that, In step S6, when the construction structure layer is a roadbed, the triangulation network data file is imported into a satellite positioning measuring instrument, and the surface layout method is used for surveying and setting out; when the construction structure layer is a concrete pavement layer, the pavement control point data file is imported into a total station, and the three-dimensional coordinate point layout method is used for surveying and setting out.

10. The surveying method according to claim 9, characterized in that, The total station is used to set up the three-dimensional coordinate points using the instrumentless elevation method.

Images