Hydrodynamic riverway grid terrain generation method based on section measurement data

Abstract

The invention provides a hydrodynamic riverway grid terrain generation method based on section measurement data, which comprises the following steps of: drawing a grid subdivision control line by combining data such as a section, an image and a shoreline; on the basis of the control lines, generating a quadrilateral unstructured grid; traversing the grid, and calculating a normal direction angle of a grid unit edge; continuously tracking from an initial unit edge, and determining the relationship between upstream and downstream and left and right banks of the grid by comparing the collinear degree of normal lines, namely determining a two-dimensional index number; calculating the mileage of the central point of each grid, the distance from the central point to the left bank, and the lengths of the transverse line and the longitudinal line; establishing an upstream and downstream one-to-one correspondence relationship between key element points of upstream and downstream sections through continuous segmentation of elevation low points; generating a new section at a transverse line through interpolation by using section point data corresponding to upstream and downstream based on mileage and considering section width change; and traversing the grids by using structured numbers, and assigning elevation attributes of the central points of the intersected grids based on new section data.

Description

Technical Field

[0001] The invention relates to the technical field of water conservancy project planning, in particular to a method for generating hydrodynamic river channel grid terrain based on cross-section measurement data. Background Art

[0002] In the practice of flood prevention and disaster reduction in the water conservancy industry, with the continuous improvement of computing power, flood risk management in the new era has become increasingly intelligent and refined. The construction of the flood prevention "four predictions" platform based on digital twin technology has put forward higher requirements for "simulation rehearsal". For the simulation of the evolution of river floods, most of them used to be based on one-dimensional river models based on the "river section-section" structure. The cross-sectional process elements (water level, flow, etc.) output by the model are difficult to fully support the rehearsal function of the river flood evolution process. For this reason, it is necessary to build a two-dimensional shallow water model covering the river range. The typical result of river topography measurement is the river cross section. How to generate river topography data suitable for two-dimensional hydrodynamic calculations based on the existing river section data is a problem in the existing technology.

[0003] In a two-dimensional hydrodynamic model, the most important role of terrain data is to assign elevation values ​​to the grid. In this sense, the ultimate goal of studying river terrain generation methods is to obtain a set of high-quality grid data with accurate elevation attribute values. Different from general two-dimensional hydrodynamic calculation scenarios, the two-dimensional hydrodynamic model of a river channel has its own particularity, that is, the water flow is generally confined to a narrow and long river channel and flows along the river channel. In view of this characteristic, the two-dimensional hydrodynamic model of a river channel should use a body-fitting grid generated with the river bank as the longitudinal control line as the calculation grid. Obviously, the existing river channel terrain generation technology in the prior art has deficiencies in the applicability of the two-dimensional hydrodynamic model of the river channel, and fails to fully consider the changes in cross-sectional morphology, especially the underwater terrain part.

[0004] The invention patent application with application publication number CN111681316A discloses a high-precision river terrain interpolation method, including: 1. Classifying the cross-section types of the measured river channel and determining the number of longitudinal control lines of the measured river channel; 2. Using the satellite image of the measured river channel as the base map, superimposing the cross-section control lines of the river channel and drawing the longitudinal control lines of the river channel; 3. Interpolating the elevation value at the intersection of the cross-section line of the river channel and the longitudinal control line according to the elevation data of the cross-section of the river channel, and interpolating the longitudinal control line into a three-dimensional curve; 4. Converting the cross-section control line of the river channel into a three-dimensional line, and generating the basic data of the three-dimensional terrain model together with the interpolated three-dimensional longitudinal control line, using the Delauany method to triangulate the interpolation area, and using the two-dimensional linear interpolation method to determine the elevation of the triangulated mesh vertices, and then generating the three-dimensional terrain model. This method only adds the control lines of the above-water terrain, and does not fully consider the improvement of the accuracy of the underwater terrain. At the same time, when there is only the river channel section data, the interpolation effect is not ideal, and the requirements of the two-dimensional hydrodynamic model for terrain data cannot be met.

[0005] The invention patent application with application publication number CN109960838A discloses a method for automatically generating river terrain that reflects the basic characteristics of a river. The method combines the measured cross-sectional data of the river with high-resolution remote sensing images or existing river vector data to extract the left and right bank (embankment) lines and the river channel deep line that reflect the basic characteristics of the river. By encrypting the middle line between the left and right bank (embankment) lines and the deep line of the river channel and intersecting it with the measured cross-sectional line of the river channel, a directional interpolation line segment of the river channel is formed, and further directional interpolation is performed to generate river channel elevation points that reflect the basic characteristics of the three lines of the river, thereby realizing the automatic generation of river channel terrain. This method requires the location of the river channel deep line to be known, and the deep line is generally located in the underwater part. When the measurement section spacing is large and the river channel morphology is more complex, the location of the deep line cannot be directly determined. Summary of the invention

[0006] In order to solve the above technical problems, the present invention proposes a method for generating hydrodynamic river grid terrain based on cross-sectional measurement data. Based on the existing cross-sectional measurement data, the key morphological elements of the upstream and downstream sections are fully considered in the spatial interpolation, and the elevation attributes of the two-dimensional body-fitting grid of the river are assigned, thereby obtaining grid terrain data suitable for two-dimensional hydrodynamic calculations of the river.

[0007] The object of the present invention is to provide a method for generating hydrodynamic river grid terrain based on cross-sectional measurement data, comprising obtaining the location of the measurement cross-sectional data, high-resolution remote sensing images, and shoreline or levee data, and further comprising the following steps:

[0008] Step 1: Based on the acquired data, draw the grid division control lines, including longitudinal control lines and transverse control lines;

[0009] Step 2: for each river section, generate the same number of control points on the longitudinal control line and the transverse control line respectively, and generate a quadrilateral grid, wherein the quadrilateral grid is an unstructured grid;

[0010] Step 3: traverse the unstructured grid and calculate the normal direction angle α of each grid unit edge, that is, the angle between the normal and the x-axis direction;

[0011] Step 4: Structuring the topological relationship of the unstructured grid, and converting the grid number into a two-dimensional index number with the longitudinal direction and the transverse direction of the river channel as the axis direction;

[0012] Step 5: Take the horizontal starting edge as the reference edge, traverse other unit edges of the grid where it is located, compare the collinearity of the normals of the current unit edge and the reference edge, and find the unit edge with the largest collinearity;

[0013] Step 6: Take each grid in the upstream of the river as the starting grid, take the grid cell edge at the most upstream of the river as the starting edge, and continuously trace the cell edge with the largest degree of collinearity of normal lines downstream, and determine the two-dimensional index numbers of the passed grids in sequence to achieve the structuring of all grid numbers;

[0014] Step 7: Define the line connecting the center points of the grids with the same longitudinal number and the center points of the outer unit edges of the left and right banks as the transverse line, and define the line connecting the center points of the grids with the same transverse number and the center points of the outermost unit edges of the upstream and downstream as the longitudinal line;

[0015] Step 8: Establish a one-to-one correspondence between the key cross-section points of the upstream and downstream cross-sections;

[0016] Step 9: According to the corresponding relationship and the position of the transverse line, linear interpolation is performed according to the distance while taking into account the change of the section width;

[0017] Step 10: Use a structured numbering system to traverse all grids, interpolate the cross-sectional data at the transverse lines where the grids are located, and assign the elevation attributes of the grid center points.

[0018] Preferably, the longitudinal control lines are left and right bank lines, and the transverse control lines include upstream and downstream cross sections and internal control lines perpendicular to the flow direction of the river.

[0019] In any of the above schemes, it is preferred that the transverse control lines divide the river channel into N sections, and each river section is surrounded by two of the transverse control lines and two of the longitudinal control lines.

[0020] In any of the above solutions, preferably, the normal direction of the grid unit edge is from the unit with a larger number to the unit with a smaller number by default, wherein the normal direction of the grid unit edge located at the boundary points outward by default.

[0021] In any of the above solutions, preferably, the coordinates of the two endpoints of the grid unit edge are (x1, y1) and (x2, y2), and the normal direction angle calculation formula of the unit edge is:

[0022]

[0023] In any of the above schemes, it is preferred that the positive direction of the longitudinal direction of the river channel is from upstream to downstream, and the positive direction of the transverse direction of the river channel is from the left bank to the right bank.

[0024] In any of the above schemes, preferably, step 5 also includes setting the upstream left bank grid point as the coordinate origin, taking the grid where this point is located as the starting grid, numbering it as (1,1), and selecting the left bank unit edge of the grid as the horizontal starting edge, and the upstream unit edge of the grid as the vertical starting edge.

[0025] In any of the above schemes, preferably, step 5 includes the following sub-steps:

[0026] Step 51: traverse other unit edges of the starting grid, compare the collinearity of the normals of the current unit edge and the reference edge, and find the unit edge with the largest collinearity as the target edge;

[0027] Step 52: adding 1 to the horizontal number in the two-dimensional index number of another grid other than the used grid that shares the same edge with the target edge;

[0028] Step 53: Take the target edge as the new reference edge, traverse other unit edges, compare the collinearity of the normals of the current unit edge and the reference edge, and find the unit edge with the largest collinearity;

[0029] Step 54: Repeat steps 52-53 until you reach the right bank.

[0030] In any of the above schemes, it is preferred that the degree of collinearity of the normals is expressed by the deviation angle d a To express it, the calculation formula is

[0031]

[0032] Among them, α b , α c They are the normal direction angles of the base edge and the current edge respectively.

[0033] In any of the above schemes, preferably, step 7 also includes using a structured numbering system to traverse all grids, calculate the mileage of each grid center point from its respective longitudinal starting unit edge and the lateral distance from its respective left bank unit edge, as well as the length of the lateral and longitudinal lines.

[0034] In any of the above solutions, preferably, step 8 includes the following sub-steps:

[0035] Step 81: Establishing a corresponding relationship between the upstream and downstream sections;

[0036] Step 82: segment the upstream and downstream sections at their respective lowest elevation points, and continue segmenting the latest left and right groups of section points at their respective lowest elevation points;

[0037] Step 83: Repeat steps 81-82 until no further segmentation is possible.

[0038] In any of the above solutions, preferably, the linear interpolation formula is:

[0039]

[0040] Among them, y represents the distance from the left bank, z represents the elevation, u and d represent the upstream and downstream respectively, i represents the sequence number of the corresponding section points of the upstream and downstream in the corresponding relationship table, ω is the weight coefficient, and c is the width scaling coefficient.

[0041] In any of the above solutions, preferably, the calculation formula of the width scaling factor c is:

[0042]

[0043] Among them, B, B u , B d They are respectively the width of the current transverse line, the upstream section width and the downstream section width.

[0044] In any of the above solutions, preferably, the calculation formula of the elevation z is:

[0045]

[0046] Among them, z k represents the elevation of the kth section point, y k represents the distance between the kth section point and the left bank. The subscripts k and k+1 represent the section point numbers generated by interpolation at the transverse line. k <y<y k+1 Indicates that the current grid center point is between two consecutive section points interpolated at the transverse line.

[0047] The present invention proposes a method for generating hydrodynamic river grid terrain based on cross-section measurement data, which can fully consider the key morphological elements of the cross section and their changes, especially the underwater part, and directly assign elevation attributes based on the unstructured body-fitting grid. The results are more suitable for the calculation of two-dimensional hydrodynamic models of rivers. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The present invention is a flowchart of a preferred embodiment of a method for generating hydrodynamic river grid terrain based on cross-sectional measurement data according to the present invention.

[0049] Figure 2 It is a flow chart of another preferred embodiment of the method for generating hydrodynamic river grid terrain based on cross-section measurement data according to the present invention.

[0050] Figure 3 A schematic diagram of control lines for drawing grid division according to an embodiment of the method for generating hydrodynamic river grid terrain based on cross-section measurement data of the present invention.

[0051] Figure 4 It is a schematic diagram of an embodiment of an unstructured grid at a certain resolution according to the method for generating hydrodynamic river grid terrain based on cross-section measurement data of the present invention.

[0052] Figure 5 It is a schematic diagram of an embodiment of the unit edge normal direction angle of the method for generating hydrodynamic river grid terrain based on cross-section measurement data according to the present invention.

[0053] Figure 6 The figure is a schematic diagram of an embodiment of the starting grid and starting unit edge of the method for generating hydrodynamic river grid terrain based on cross-section measurement data according to the present invention.

[0054] Figure 7 A partial schematic diagram of an embodiment of structured two-dimensional index numbering of a method for generating hydrodynamic river grid terrain based on cross-sectional measurement data according to the present invention.

[0055] Figure 8 It is a partial schematic diagram of a red horizontal line and a blue vertical line of an embodiment of a method for generating hydrodynamic river grid terrain based on cross-section measurement data according to the present invention.

[0056] Fig. 9 It is a schematic diagram of an embodiment of the correspondence between upstream and downstream of cross-section points according to the method for generating hydrodynamic river grid terrain based on cross-section measurement data of the present invention.

[0057] Fig.10 The figure is a result schematic diagram of an embodiment of a river channel topography generated by a method for generating hydrodynamic river channel grid topography based on cross-section measurement data according to the present invention. DETAILED DESCRIPTION

[0058] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0059] Embodiment 1

[0060] like Figure 1 As shown, a method for generating hydrodynamic river grid terrain based on cross-section measurement data is performed, step 1000 is executed to obtain the location of the measurement cross-section data, high-resolution remote sensing images, and shoreline or levee data,

[0061] Execute step 1010, and draw grid division control lines in combination with the acquired data, including longitudinal control lines and transverse control lines. The longitudinal control lines are the left and right bank lines, and the transverse control lines include upstream and downstream cross sections and internal control lines perpendicular to the flow direction of the river. The transverse control lines divide the river into N sections, and each river section is surrounded by two of the transverse control lines and two of the longitudinal control lines.

[0062] Execute step 1020 to generate the same number of control points on the longitudinal control line and the transverse control line for each river section, and generate a quadrilateral grid, where the quadrilateral grid is an unstructured grid.

[0063] Execute step 1030, traverse the unstructured grid, calculate the normal direction angle α of each grid unit edge, that is, the angle between the normal and the x-axis direction, the normal direction of the grid unit edge is from the unit with a larger number to the unit with a smaller number by default, wherein the normal direction of the grid unit edge located at the boundary points outward by default. The coordinates of the two endpoints of the grid unit edge are (x1, y1) and (x2, y2), respectively, and the calculation formula of the normal direction angle of the unit edge is:

[0064]

[0065] Execute step 1040 to structure the topological relationship of the unstructured grid, convert the grid number into a two-dimensional index number with the longitudinal direction and the transverse direction of the river channel as the axis direction, and take from upstream to downstream as the positive direction of the longitudinal direction of the river channel, and take from left bank to right bank as the positive direction of the transverse direction of the river channel.

[0066] Execute step 1050, take the horizontal starting edge as the reference edge, traverse other unit edges of the grid where it is located, compare the collinearity of the normals of the current unit edge and the reference edge, find the unit edge with the largest collinearity, set the left bank grid point on the most upstream side as the coordinate origin, take the grid where this point is located as the starting grid, number it as (1,1), and select the left bank unit edge of the grid as the horizontal starting edge, and the upstream unit edge of the grid as the vertical starting edge, including the following sub-steps:

[0067] Execute step 1051, traverse the other unit edges of the starting grid, compare the collinearity of the normals of the current unit edge and the reference edge, find the unit edge with the largest collinearity, and use it as the target edge. The collinearity of the normals is expressed by the deviation angle d a To express it, the calculation formula is

[0068]

[0069] Among them, α b , α c They are the normal direction angles of the base edge and the current edge respectively.

[0070] Step 1052 is executed to increase the horizontal number in the two-dimensional index number of another grid other than the used grid that shares the same edge with the target edge by 1.

[0071] Execute step 1053, take the target edge as the new reference edge, traverse other unit edges, compare the collinearity of the normals of the current unit edge and the reference edge, and find the unit edge with the largest collinearity.

[0072] Execute step 1054 and repeat steps 1052-1053 until reaching the right bank.

[0073] Execute step 1060, take each grid upstream of the river channel as the starting grid, take the grid cell edge upstream of the river channel as the starting edge, and continuously trace the cell edge with the largest degree of collinearity of normals downstream, and determine the two-dimensional index numbers of the passed grids in sequence to achieve structuring of all grid numbers.

[0074] Execute step 1070, define the line connecting the center points of the grids with the same longitudinal number and the center points of the transverse outer unit edges as transverse lines, and define the line connecting the center points of the grids with the same transverse number and the center points of the longitudinal outermost unit edges as longitudinal lines. Use the structured numbering system to traverse all grids, calculate the mileage of each grid center point from its respective longitudinal starting unit edge and the transverse distance from its respective left bank unit edge, as well as the length of the transverse and longitudinal lines.

[0075] Execute step 1080 to establish a one-to-one correspondence between the key cross-section points of the upstream and downstream cross-sections, including the following sub-steps:

[0076] Execute step 1080 to establish a corresponding relationship between the upstream and downstream sections;

[0077] Execute step 1080 to segment the upstream and downstream sections based on their respective lowest elevation points, and continue to segment the latest two groups of left and right section points based on their respective lowest elevation points;

[0078] Execute step 1080, and repeat steps 1081-1082 until the segment cannot be split any further.

[0079] Execute step 1090, and perform linear interpolation according to the corresponding relationship and the position of the transverse line, according to the distance and considering the change of the cross-sectional width. The linear interpolation formula is:

[0080]

[0081] Among them, y represents the distance from the left bank, z represents the elevation, u and d represent the upstream and downstream respectively, i represents the order number of the corresponding cross-section points in the upstream and downstream in the corresponding relationship table, ω is the weight coefficient, and c is the width scaling coefficient. The calculation formula is:

[0082]

[0083] Among them, B, B u , B d They are respectively the width of the current transverse line, the upstream section width and the downstream section width.

[0084] Execute step 1100, use the structured numbering system to traverse all grids, use the interpolated cross-section data at the transverse line where the grid is located, and assign the elevation attribute of the center point of the grid. The calculation formula of the elevation z is

[0085]

[0086] Among them, z k represents the elevation of the kth section point, y k represents the distance between the kth section point and the left bank. The subscripts k and k+1 represent the section point numbers generated by interpolation at the transverse line. k <y<y k+1 Indicates that the current grid center point is between two consecutive section points interpolated at the transverse line.

[0087] Embodiment 2

[0088] The present invention provides a method for generating a two-dimensional hydrodynamic river grid terrain based on cross-sectional measurement data. The specific technical scheme is as follows:

[0089] like Figure 2 As shown, a method for generating a two-dimensional hydrodynamic river grid terrain based on cross-sectional measurement data comprises the following steps:

[0090] Step 1: Combine the location of the measured section data, high-resolution remote sensing images, and shoreline or levee data to draw grid division control lines, including longitudinal and transverse control lines. The longitudinal control lines mainly refer to the left and right shorelines, and the transverse control lines include the upstream and downstream cross-sections and the internal control lines perpendicular to the river flow direction. Especially at the bends of the river, the number of transverse control lines needs to be increased to improve the grid quality. The transverse control lines divide the river into several sections, and each section is surrounded by two transverse control lines and two longitudinal control lines.

[0091] Step 2: For each river section, generate the same number of control points on the horizontal and vertical control lines, and then generate a quadrilateral mesh. The quadrilateral mesh generated in this step is an unstructured mesh, that is, the topological relationship is unstructured.

[0092] Step 3: Traverse the above unstructured grid and calculate the normal direction angle α of each grid cell edge, that is, the angle between the normal and the x-axis direction, in the range of (-π,π]. The normal direction of the cell edge is from the cell with a larger number to the cell with a smaller number by default. The normal direction of the cell edge at the boundary points outward by default. Assume that the coordinates of the two endpoints of the cell edge are (x1, y1) and (x2, y2) respectively. The calculation formula of the normal direction angle of the cell edge is:

[0093]

[0094] Step 4: In order to clarify the relative position relationship of each grid, the topological relationship of the above unstructured grid is structured, that is, the grid number (for the convenience of expression, this number is referred to as the global number below) is converted into a two-dimensional index number with the longitudinal direction of the river (from upstream to downstream as the positive direction) and the transverse direction (from the left bank to the right bank as the positive direction) as the axis direction. Set the left bank grid point on the uppermost stream as the coordinate origin, and take the grid where this point is located as the starting grid, with the number set to (1,1), and select the left bank unit edge of the grid as the transverse starting edge, and the upstream unit edge of the grid as the longitudinal starting edge.

[0095] Step 5: Take the horizontal starting edge as the reference edge (located on the left bank), traverse the other unit edges of the grid where it is located (that is, the starting grid with the two-dimensional index number (1,1)), compare the collinearity of the normals of the current unit edge and the reference edge, and find the unit edge with the largest collinearity. For the sake of convenience, the unit edge with the largest collinearity is called the target edge. At this time, add 1 to the horizontal number in the two-dimensional index number of another grid other than the starting grid that shares the same edge with the target edge, that is, the number is (2,1). Use the target edge as the new reference edge and repeat step 5 until you reach the right bank. At this point, the row of grids upstream of the river channel completes the structural numbering. Among them, the degree of collinearity of the normal is expressed by the deviation angle d α To express it, the calculation formula is

[0096]

[0097] In the formula, α b , α c They are the normal direction angles of the base edge and the current edge respectively.

[0098] Step 6: Compare with step 5, take each grid at the uppermost reaches of the river as the starting grid, take the grid cell edge at the uppermost reaches of the river as the starting edge, and continuously track the cell edge with the largest degree of collinearity of normal lines downstream, and determine the two-dimensional index numbers of the passed grids in turn to achieve the structuring of all grid numbers. So far, in addition to the original global number, each grid also has a two-dimensional index number that indicates its relative position in the entire set of grids. For example, the two-dimensional index number of the grid with global number 235 is (4,34), indicating that the grid is located in the 34th row from the upstream section and the 4th column from the left bank.

[0099] Step 7: Define the line connecting the center points of the grids with the same longitudinal number and the center points of the outermost (left and right banks) unit edges as the transverse line, and define the line connecting the center points of the grids with the same transverse number and the center points of the outermost (upstream and downstream sections) unit edges as the longitudinal line. Using the structured numbering system, traverse all grids, calculate the distance of each grid center point from the respective longitudinal starting unit edge and the transverse distance from the respective left bank unit edge, as well as the length of the transverse and longitudinal lines.

[0100] Step 8: Establish a one-to-one correspondence between the key section points of the upstream and downstream sections for subsequent interpolation calculations. The left and right bank section points are key elements, and the correspondence is first established between the upstream and downstream sections. In addition, while establishing the upstream and downstream correspondence at the lowest elevation point, the upstream and downstream sections are segmented at their respective lowest elevation points, and the latest left and right groups of section points are further segmented at their respective lowest elevation points. While establishing the upstream and downstream correspondence at the newly obtained lowest elevation point, continue to repeat the above segmentation and correspondence process until it can no longer be segmented.

[0101] Step 9: Based on the correspondence between the upstream and downstream section points established in step 8, perform linear interpolation at the position of the transverse line obtained in step 7 according to the distance while considering the change in section width

[0102]

[0103] In the formula, y represents the distance from the left bank; z represents the elevation; superscripts u and d represent the upstream and downstream, respectively; subscript i represents the corresponding cross-section points of the upstream and downstream; ω is the weight coefficient, whose value is equal to the mileage of the transverse line to be interpolated (the distance from the upstream cross-section) and the mileage between the upstream and downstream cross-sections; c is the width scaling coefficient, and the calculation formula is:

[0104]

[0105] In the formula, B, B u , B d They are respectively the width of the current transverse line, the upstream section width and the downstream section width.

[0106] Step 10: Using the structured numbering system, traverse all grids, use the interpolated cross-section data (generated by step 9) at the transverse line where the grid is located, and assign the elevation attribute of the center point of the grid. The calculation formula is:

[0107]

[0108] Where, the subscripts k and k+1 represent the section point numbers generated by interpolation at the transverse line (numbered starting from the left bank), y k <y<y k+1 Indicates that the current grid center point is between two consecutive section points interpolated at the transverse line.

[0109] By adopting the above technical solution, the characteristics of the present invention are mainly reflected in the following aspects:

[0110] (1) The basic grid adopts the unstructured grid topology that is more commonly used in practice. By structuring it, the relative position of each grid space can be determined, which is more compatible with the existing cross-section data structure (based on mileage-distance left bank distance-elevation) and facilitates subsequent interpolation.

[0111] (2) In terms of spatial interpolation, the corresponding interpolation relationships are automatically established between the key element points of adjacent upstream and downstream sections, such as the left and right banks, the lowest point, the second lowest point, the second lowest point, and so on, to fully consider the key information of the cross section.

[0112] Based on the above characteristics, compared with the existing river terrain generation technology, the technical method proposed in this patent can fully consider the key morphological elements of the cross section and their changes, especially the underwater part, and directly assign elevation attributes based on the unstructured body-fitting grid. The results are more suitable for the calculation of two-dimensional hydrodynamic models of rivers.

[0113] Embodiment 3

[0114] A method for generating two-dimensional hydrodynamic river grid terrain based on cross-sectional measurement data, the implementation steps are as follows:

[0115] Step 1: Between the upstream and downstream measurement sections, such as Figure 2 As shown, combined with high-resolution remote sensing images, the longitudinal and transverse control lines of the grid division are drawn. At the bend of the river, the number of transverse control lines is increased to improve the quality of the grid. In this embodiment, the river section is divided into 9 sections by transverse control lines, and each river section is surrounded by two transverse control lines and two longitudinal control lines. Tables 1 and 2 are respectively the given upstream and downstream section measurement data, the first line in the table is the distance from the left bank, and the second line is the elevation, both in m.

[0116] Table 1 Upstream section measurement data

[0117] y 0.0 2.6 2.6 5.2 54.2 56.8 59.4 59.4 61.9 69.7 72.3 72.3 74.8 74.8 77.4 80.0 z 8.1 7.1 6.1 5.1 4.1 4.1 3.1 2.1 1.1 1.1 2.1 3.1 4.1 5.1 7.1 8.1

[0118] Table 2 Downstream section measurement data

[0119] y 0.0 2.9 2.9 5.9 5.9 8.8 8.8 11.7 20.5 23.5 23.5 26.4 29.3 32.3 85.0 88.0 88.0 90.9 z 7.2 6.2 5.2 4.2 3.2 2.2 1.2 0.2 0.2 1.2 2.2 3.2 3.2 3.9 4.2 5.2 6.2 7.2

[0120] Step 2: For each river section, set an equal number of control points on the horizontal and vertical control lines to generate a quadrilateral grid, such as Figure 3 A partial display of river section ④ in the middle. Figure 4 is an unstructured grid at a certain resolution of this embodiment.

[0121] Step 3: Traverse all grids and calculate the direction angle α of the normal line of each grid cell edge (from the cell with a larger number to the cell with a smaller number), such as Figure 5 shown.

[0122] Step 4: Set the left bank grid point on the farthest upstream as the coordinate origin, and the grid where this point is located as the starting grid, number it as (1,1), and select the left bank unit edge of the grid as the horizontal starting edge, and the upstream unit edge of the grid as the vertical starting edge, such as Figure 6shown.

[0123] Step 5: Take the horizontal starting edge as the reference edge, traverse the other unit edges of the grid where it is located (that is, the starting grid with the two-dimensional index number (1,1)), compare the collinearity of the normals of the current unit edge and the reference edge, find the unit edge with the largest collinearity, and define it as the target edge. Add 1 to the horizontal number in the two-dimensional index number of another grid other than the starting grid that shares the same edge with the target edge, that is, the number is (2,1). Use the target edge as the new reference edge and repeat step 5 until you reach the right bank. At this point, the row of grids upstream of the river channel completes the structural numbering.

[0124] Step 6: Compare with step 5, take each grid at the uppermost reaches of the river as the starting grid, take the grid cell edge at the uppermost reaches of the river as the starting edge, and continuously trace the cell edge with the largest degree of collinearity of normal lines downstream, and set the two-dimensional index number of the passed grids in sequence to achieve the structuring of all grid numbers. After steps 5 and 6, the local example of grid structured numbering is as follows Figure 7 shown.

[0125] Step 7: If Figure 8 As shown, the line connecting the center points of the grids with the same longitudinal number and the center points of the outermost (left and right banks) unit edges in the transverse direction is defined as a transverse line, and the line connecting the center points of the grids with the same transverse number and the center points of the outermost (upstream and downstream sections) unit edges in the longitudinal direction is defined as a longitudinal line. Using the structured numbering system, all grids are traversed to calculate the distance of each grid center point from the respective longitudinal starting unit edge and the transverse distance from the respective left bank unit edge, as well as the length of the transverse and longitudinal lines, in preparation for the subsequent section interpolation calculation.

[0126] Step 8: The left and right bank section points are used as key elements, and a corresponding relationship is first established between the upstream and downstream sections. In addition, while the upstream and downstream corresponding relationship is established at the lowest elevation point, the upstream and downstream sections are segmented at their respective lowest elevation points, and the latest left and right groups of section points segmented are further segmented at their respective lowest elevation points. While the upstream and downstream corresponding relationship is established at the newly obtained lowest elevation point, the above segmentation and corresponding relationship establishment process is continued until no further segmentation is possible. In this embodiment, the upstream and downstream corresponding relationship of the section points is shown in Table 3 and Fig. 9 shown.

[0127] Table 3. One-to-one correspondence table of upstream and downstream cross-section points

[0128]

[0129]

[0130] Step 9: Based on the correspondence between the upstream and downstream section points established in step 8, at the position of the transverse line obtained in step 7, linear interpolation is performed according to the distance and considering the change in section width to obtain the cross-sectional shape data at the transverse line.

[0131] Step 10: Using the structured numbering system, traverse all grids, use the cross-sectional shape data (generated by step 9) at the transverse line where the grid is located to interpolate the elevation attribute of the grid center point through spatial interpolation. The interpolation result is as follows: Fig.10 shown.

[0132] In order to better understand the present invention, the above is described in detail in conjunction with the specific embodiments of the present invention, but it is not intended to limit the present invention. Any simple modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention. Each embodiment in this specification focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referenced to each other. For the system embodiment, since it basically corresponds to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

Claims

1. A method for generating hydrodynamic river grid terrain based on cross-sectional measurement data, comprising obtaining the location of the measurement cross-sectional data, high-resolution remote sensing images, and shoreline or levee data, and further comprising the following steps: Step 1: Based on the acquired data, draw the grid division control lines, including longitudinal control lines and transverse control lines; Step 2: for each river section, generate the same number of control points on the longitudinal control line and the transverse control line respectively, and generate a quadrilateral grid, wherein the quadrilateral grid is an unstructured grid; Step 3: traverse the unstructured grid and calculate the normal direction angle α of each grid unit edge, that is, the angle between the normal and the x-axis direction; Step 4: Structuring the topological relationship of the unstructured grid, and converting the grid number into a two-dimensional index number with the longitudinal direction and the transverse direction of the river channel as the axis direction; Step 5: Take the horizontal starting edge as the reference edge, traverse other unit edges of the grid where it is located, compare the collinearity of the normals of the current unit edge and the reference edge, and find the unit edge with the largest collinearity; Step 6: Take each grid in the upstream of the river as the starting grid, take the grid cell edge at the most upstream of the river as the starting edge, and continuously trace the cell edge with the largest degree of collinearity of normal lines downstream, and determine the two-dimensional index numbers of the passed grids in sequence to achieve the structuring of all grid numbers; Step 7: Define the line connecting the center points of the grids with the same longitudinal number and the center points of the outer unit edges of the left and right banks as the transverse line, and define the line connecting the center points of the grids with the same transverse number and the center points of the outermost unit edges of the upstream and downstream as the longitudinal line; Step 8: Establish a one-to-one correspondence between the key cross-section points of the upstream and downstream cross-sections; Step 9: According to the corresponding relationship and the position of the transverse line, linear interpolation is performed according to the distance while taking into account the change of the cross-section width; Step 10: Use a structured numbering system to traverse all grids, interpolate the cross-sectional data at the transverse lines where the grids are located, and assign the elevation attributes of the grid center points.

2. The method for generating hydrodynamic river grid terrain based on cross-sectional measurement data according to claim 1, characterized in that: The longitudinal control lines are the left and right bank lines, the transverse control lines include the upstream and downstream cross sections and the internal control lines perpendicular to the flow direction of the river channel, and the transverse control lines divide the river channel into N sections, and each river section is surrounded by two of the transverse control lines and two of the longitudinal control lines.

3. The method for generating hydrodynamic river grid terrain based on cross-sectional measurement data according to claim 2, characterized in that: The normal direction of the mesh unit edge is from the unit with a larger number to the unit with a smaller number by default, wherein the normal direction of the mesh unit edge located at the boundary points outward by default.

4. The method for generating hydrodynamic river grid terrain based on cross-sectional measurement data according to claim 3, characterized in that: The coordinates of the two endpoints of the grid unit edge are (x1, y1) and (x2, y2), and the normal direction angle calculation formula of the unit edge is:

5. The method for generating hydrodynamic river grid terrain based on cross-sectional measurement data according to claim 4, characterized in that: The step 5 also includes setting the upstream left bank grid point as the coordinate origin, taking the grid where this point is located as the starting grid, numbering it as (1,1), and selecting the left bank unit edge of the grid as the horizontal starting edge, and the upstream unit edge of the grid as the vertical starting edge.

6. The method for generating hydrodynamic river grid terrain based on cross-sectional measurement data according to claim 5, characterized in that: The step 5 comprises the following sub-steps: Step 51: traverse other unit edges of the starting grid, compare the collinearity of the normals of the current unit edge and the reference edge, and find the unit edge with the largest collinearity as the target edge; Step 52: adding 1 to the horizontal number in the two-dimensional index number of another grid other than the used grid that shares the same edge with the target edge; Step 53: Take the target edge as the new reference edge, traverse other unit edges, compare the collinearity of the normals of the current unit edge and the reference edge, and find the unit edge with the largest collinearity; Step 54: Repeat steps 52-53 until you reach the right bank.

7. The method for generating hydrodynamic river grid terrain based on cross-sectional measurement data according to claim 6, characterized in that: The degree of collinearity of normals is expressed as the deviation angle d a To express it, the calculation formula is Among them, α b , α c They are the normal direction angles of the base edge and the current edge respectively.

8. The method for generating hydrodynamic river grid terrain based on cross-sectional measurement data according to claim 7, characterized in that: The step 7 also includes using a structured numbering system to traverse all grids, calculate the distance of each grid center point from its respective longitudinal starting unit edge and its lateral distance from its respective left bank unit edge, and the length of the lateral and longitudinal lines.

9. The method for generating hydrodynamic river grid terrain based on cross-sectional measurement data according to claim 8, characterized in that: The step 8 comprises the following sub-steps: Step 81: Establishing a corresponding relationship between the upstream and downstream sections; Step 82: segment the upstream and downstream sections at their respective lowest elevation points, and continue segmenting the latest left and right groups of section points at their respective lowest elevation points; Step 83: Repeat steps 81-82 until no further segmentation is possible.

10. The method for generating hydrodynamic river grid terrain based on cross-sectional measurement data according to claim 9, characterized in that: The linear interpolation formula is: Among them, y represents the distance from the left bank, z represents the elevation, u and d represent the upstream and downstream respectively, i represents the order number of the corresponding cross-section points of the upstream and downstream in the corresponding relationship table, ω is the weight coefficient, and c is the width scaling coefficient. Among them, B, B u , B d They are respectively the width of the current transverse line, the upstream section width and the downstream section width.

Images