River flood routing grid model dynamic display method based on Cesium three-dimensional scene, readable storage medium and program product

Abstract

The invention belongs to the technical field of flood scene simulation, and particularly relates to a river flood routing grid model dynamic display method based on a Cesium three-dimensional scene, a readable storage medium and a program product. The method comprises the following steps: firstly, preprocessing Cesium three-dimensional scene geographic data for Cesium three-dimensional scene construction work; secondly, utilizing a two-dimensional hydrodynamic model of HEC-RAS software to construct an unstructured river flood routing grid model; then, converting a calculation result of the river flood routing grid model into a data format which can be identified by a Cesium three-dimensional scene; then, processing the preliminarily established unstructured river flood routing grid model again, and converting the preliminarily established unstructured river flood routing grid model into a structured river flood routing grid model; and finally, displaying the constructed river flood routing grid model in a Cesium three-dimensional scene. According to the method, the dynamic visualization effect and the rendering efficiency of the river flood routing are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of flood scene simulation, and specifically relates to a method for dynamically displaying a river flood evolution grid model based on a Cesium three-dimensional scene, a readable storage medium, and a program product. Background Art

[0002] As traditional two-dimensional data can no longer meet the requirements of building a smart platform, it is necessary to intuitively display traditional two-dimensional tabular data in the constructed virtual scene, combine real data with three-dimensional scenes, and build a virtual reality flood simulation experience.

[0003] Due to the terrain and rainfall in my country, downstream rivers near reservoirs are prone to flooding. The flood evolution model generated by the existing HEC-RAS two-dimensional hydrodynamic model can already meet the flood evolution effect of most scenarios. However, because it is an unstructured model and the river terrain has certain particularities, the terrain is complex and the width is narrow, the unstructured river flood evolution grid model generated by HEC-RAS cannot well meet the display effect required by the present invention, and in terms of efficiency, directly rendering its evolution data cannot meet the requirement of at least 30 FPS.

[0004] Chinese patent document CN118171441A discloses a flood evolution simulation method and system based on three-dimensional visualization. It constructs a reservoir-related three-dimensional model through three-dimensional modeling technology, and restores the reservoir and basin scene; collects historical reservoir water and rainfall data and flood-related variable data to generate historical flood scenes; constructs a historical flood scene database, analyzes the deviation between the historical flood scene database and the historical forecast data, and generates a historical flood big data model; generates data related to the pre-drill flood discharge plan based on the historical flood big data model, and displays the flood evolution process in three-dimensional visualization. The historical flood big data model is combined with the reservoir and basin scene to realize the integration of flood process simulation and three-dimensional scene, providing an intuitive basis for flood prevention and disaster reduction measures. However, the invention still needs to be combined with historical big data and other related information to analyze the flood evolution process, and the operating efficiency is not high.

[0005] Therefore, it is necessary to build a three-dimensional flood evolution simulation model based on the downstream river channel, and build a river flood evolution grid model based on the two-dimensional hydrodynamic model. The evolution model is reconstructed while taking into account relatively accurate data simulation. It can simplify mathematical theory, reduce the amount of calculation, and ensure visualization effects. It can also run smoothly on the B-end and can be used for water flow movement in the downstream river channel near the reservoir. The river flood evolution simulation model can simulate the damage of floods to villages near the river channel, so that better information decisions can be made for relevant personnel.

[0006] In summary, the present invention proposes a method for dynamically displaying a river flood evolution grid model based on a Cesium three-dimensional scene to simulate and predict the flood inundation process of a river. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention discloses a method for dynamically displaying a river flood evolution grid model based on a Cesium three-dimensional scene.

[0008] The invention also discloses a computer-readable storage medium for implementing the above method.

[0009] The invention also discloses a program product for realizing the method. Summary of the invention:

[0011] The present invention constructs basic geographic data and reservoir discharge data of the study area, trains the two-dimensional hydrodynamic model module of the HEC-RAS software to improve the accuracy of the evolution results of the study area, converts the format of the results, and performs structural meshing processing on the grid vertices of the evolution model based on the Delaunny triangulation of the three-dimensional model and the Bowyer-Watson algorithm to improve the loading efficiency of the evolution model in the Cesium three-dimensional scene. At the same time, color texture mapping operations are performed on the grid points according to the water level and water depth element values ​​to improve the visualization effect of the evolution model in the three-dimensional scene.

[0012] The technical solution adopted by the present invention to achieve the above purpose is:

[0013] A method for dynamically displaying a river flood evolution grid model based on a Cesium three-dimensional scene, characterized in that it comprises the following steps:

[0014] A. Cesium 3D scene geographic data preprocessing is used for Cesium 3D scene construction. The basic image of the study area is constructed by controlling, orienting, and correcting the image map DOM digital data generated by drone aerial photos, and the DEM data collected by laser radar is used to produce river terrain data, thereby constructing a virtual 3D scene of the study area;

[0015] B. Pre-construction of river flood evolution grid model: using the two-dimensional hydrodynamic model of HEC-RAS software to construct an unstructured river flood evolution grid model;

[0016] C. Conversion of calculation results of river flood evolution grid model, used for format conversion, into data format that can be recognized by Cesium 3D scene;

[0017] D. Reconstruct the river flood evolution grid model, reprocess the initially established unstructured river flood evolution grid model and convert it into a structured river flood evolution grid model, so as to improve the loading efficiency while ensuring the visualization effect;

[0018] E. Dynamic display of river flood evolution grid model. For the constructed river flood evolution grid model, the river flood evolution grid model is displayed in the Cesium three-dimensional scene according to the vertex order, depth and water level elements of this evolution model.

[0019] As a further technical solution of the present invention, the Cesium three-dimensional scene geographic data preprocessing refers to using the river DEM data and DOM digital data of the study area as the basic data for scene construction, and using ArcGIS software to eliminate data that does not conform to the study area, and converting the two into a data structure that can be rendered by Cesium through Cesiumlab, and displaying it as a virtual three-dimensional scene in the Cesium three-dimensional scene.

[0020] As a further technical solution of the present invention, the pre-construction of the river flood evolution grid model means that first, DEM data is imported through the HEC-RAS software, and then grid and terrain interpolation are performed on it, and then the measured flow data is used for the inflow boundary to perform unsteady flow analysis UnsteadyFlowAnalysis, and the normal water depth NormalDepth boundary condition provided by the HEC-RAS model is used for the outflow boundary. The water level is solved at the boundary by the steady flow equation, and the model operation parameters are set. The model operation parameters include the time step, the time interval of the flood evolution animation, the weight parameter and the calculation equation, and then according to the set model operation parameters, the hydrodynamic model is run to calculate the water level, flow velocity and flow elements in the river system and the flood protection area. Different calculation equations are selected to obtain different results;

[0021] As a further technical solution of the present invention, the water level and the flow rate are calculated based on the two-dimensional simplified form of the Navier-Stokes equation - the shallow water equation, and the flow rate is calculated based on the water-passing cross-sectional area and the average flow rate of the cross-section.

[0022] As a further technical solution of the present invention, the conversion of the calculation results of the river flood evolution grid model refers to converting the unstructured river flood evolution grid model obtained by the HEC-RAS software, using Python to further parse the obtained evolution model calculation results and convert them into a general JSON format to save them for subsequent operations.

[0023] As a further technical solution of the present invention, the reconstruction of the river flood evolution grid model refers to the structural gridding of the initially established unstructured river flood evolution grid model, thereby improving the loading effect of the model: the grid is divided by the Delaunay triangulation grid generation algorithm of the three-dimensional model and the grid vertices are re-triangulated according to the Bowyer-Watson algorithm, and its grid structure is converted from unstructured to structured, and a linear relationship is established between the elevation value of the DEM data and the water level of the river flood evolution grid model, and stored in the evolution model.

[0024] As a further technical solution of the present invention, the dynamic display module of the river flood evolution grid model assigns different color textures to the grid vertices of the reconstructed river flood evolution grid model according to the water level value, and the animation evolution effect of the river flood evolution grid model is displayed in the Cesium three-dimensional scene.

[0025] A computer-readable storage medium stores computer instructions, which can implement the steps of the above method when executed by a processor.

[0026] A computer program product loaded with the above method comprises computer instructions, which can implement the steps of the above method when executed by a processor.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention generates a river flood evolution grid model based on the two-dimensional hydrodynamic model of HEC-RAS, and ensures the model rendering efficiency while ensuring the grid display effect of the evolution model by structurally processing the grid structure of the evolution model.

[0029] (2) The present invention dynamically displays in the form of general mesh vertices, establishes corresponding relationships between mesh vertices and corresponding water level values, as well as between water level values ​​and DEM data, can express the main locations where river floods occur, and establishes color-texture mapping relationships between mesh vertices and water level values. The colors between mesh vertices are linearly colored based on the evolution of two adjacent mesh vertices, which can provide a more intuitive display effect. In addition, there is no need to load too many texture objects. Only mesh vertices need to be rendered to express the dynamic effect of river flood evolution, thereby ensuring the display effect while meeting the operating efficiency.

[0030] (3) The present invention uses the two-dimensional simplified form of the Navier-Stokes equations - the calculation results of the shallow water equation to pre-construct the river flood evolution grid model for river data, and then reconstructs the evolution model through Delaunay triangulation and Bowyer-Watson algorithm. Although the model construction process is increased from one step to two steps, the calculation process of the model is reduced. Only by performing a simple grid structure improvement on the river flood evolution grid model generated by HEC-RAS based on the existing mature model through Delanunay and Bowyer-Waston algorithms, a model that meets the requirements of the present invention can be generated without complex calculations.

[0031] (4) The present invention is based on the three-dimensional GIS rendering engine Cesium, which can better combine the model of the present invention with the virtual geographic scene, highlight the application of river flood disasters in real scenes, and provide certain reference opinions for river flood disasters that may occur in reality. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural diagram of a method for dynamically displaying a river flood evolution grid model based on a Cesium scene provided by the present invention. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. The embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0034] Embodiment 1,

[0035] like Figure 1 As shown, a method for dynamically displaying a river flood evolution grid model based on a Cesium scene includes a Cesium three-dimensional scene geographic data preprocessing module, a river flood evolution grid model pre-construction module, a grid model calculation result conversion module, a river flood evolution grid model reconstruction module, and a river flood evolution grid model dynamic display module. The above modules are integrated to construct a high-precision river flood evolution grid model, and dynamically display it in the three-dimensional rendering engine Cesium. The steps are as follows:

[0036] Step 1: Cesium real scene construction, DOM obtained by drone aerial photography and DEM obtained by lidar scanning, and ArcGIS geoprocessing software are used to eliminate the research area data not needed by the present invention from the research data, and then the basic image and terrain data required by the present invention are generated by Cesiumlab software, and finally loaded into the corresponding position in the Cesium three-dimensional scene.

[0037] Step 2: Pre-construction of river flood evolution grid model. The hydrodynamic model of HEC-RAS software is used to construct a two-dimensional river flood evolution grid model. First, the 15-kilometer river downstream of the target river is extracted, the terrain is imported, the grid is drawn according to the accuracy requirements, the terrain is interpolated, and the basic data such as the DEM digital elevation model is combined with the corresponding projection file. The reservoir discharge data and other data are Kriging interpolated according to the resolution of the DEM data to draw the grid, determine the boundary, set the model operation parameters, and run the hydrodynamic model to calculate the flow through the water section area and the average flow velocity of the section. The main calculation process is:

[0038] Step 2.1: Import terrain. Create a new project file (.prj) in HEC-RAS and change the imperial units to international standard units. On this basis, import the acquired high-precision DEM (including river channels and floodplains) and the corresponding projection coordinate file into the model.

[0039] Step 2.2: Draw the grid and interpolate the terrain. The HEC-RAS computational grid uses an unstructured grid, with irregular polygons at the boundaries and squares inside. When drawing the grid, you need to set relevant parameters such as the size of a single grid and give the roughness value of the entire area. In addition, the generated grid is corrected to improve the model stability, and the elevation is extracted from the RAS terrain data and assigned to the computational grid.

[0040] Step 2.3: Determine the boundary. The upper boundary (inflow boundary) uses the measured flow data to perform unsteady flow analysis (UnsteadyFlowAnalysis); the lower boundary (outflow boundary) uses the normal depth (NormalDepth) boundary condition of the HEC-RAS model, and the steady flow equation is used to solve the water level at the boundary.

[0041] Step 2.4: Initial Conditions Setting. Initial conditions are used to describe the initial state of the entire model. To ensure the simulation effect, the initial water level is set to 0, that is, the dry riverbed state.

[0042] Step 2.5: Set the model running parameters. This mainly includes the following steps:

[0043] Step 2.5.1: The calculation time step (ComputationInterval) adopts variable time step control (AdvancedTimeStepControl), and the maximum Courant number (MaximumCourant) is controlled at 1.0 or below 1.0.

[0044] Step 2.5.2: The time interval (number of frames) (MappingOutputInterval) for generating the river flood evolution animation is determined to be 30 minutes according to the requirements.

[0045] Step 2.5.4: The weight parameter (Theta) defaults to 1.0.

[0046] Step 2.5.5: Calculation equation selection. The calculation equation (Equatiionset) uses the two-dimensional simplified form of the Vener-Stokes equation, which is faster and more stable, the shallow water equation. This equation is calculated through the momentum equation and the continuity equation, as follows:

[0047] The momentum equation is as follows:

[0048]

[0049] In formula (1), V is the flow velocity (m / s); g is the gravitational acceleration (m / s 2 ) ; H is the water surface elevation (m); V t is the horizontal kinematic viscosity (m 2 / s);c f is the roughness of the riverbed bottom; f is the Coriolis coefficient; k is the unit vector in the vertical direction;

[0050] The continuity equation is as follows:

[0051]

[0052] In formula (2), H is the water surface elevation (m); h is the water depth (m); V is the flow velocity (m / s); q is the side inflow (m 2 / s);

[0053] The two-dimensional simplified form - shallow water equation is derived, and the calculation equation is as follows:

[0054]

[0055] In formula (3), H is the water surface elevation (m); V is the flow velocity (m / s); R is the hydraulic radius (m); and n is the roughness.

[0056] Step 2.6: Run the hydrodynamic model. According to the model's preliminary settings, run the hydrodynamic model to calculate flood inundation elements such as water level, flow velocity, and flow rate in the river system and flood protection area. The water depth and flow rate are calculated based on the two-dimensional simplified form of the Navier-Stokes equation - the shallow water equation, and the flow rate is calculated based on the cross-sectional area and the average flow velocity of the cross section:

[0057] Step 3: Data format conversion. First, ArcGIS software is used to retain the water level and flow process of each monitoring section, the flooding process of key areas, and the flood velocity, flooding depth and flooding duration within the flooding range. Then, Python is used to process and convert the calculation results into a JSON format that can be loaded by Cesium.

[0058] Step 4: Convert the calculation result grid data into structure, which mainly includes the following steps:

[0059] Step 4.1: Establish a spatial triangular mesh structure. The data results after simulation are obtained through the Delaunay triangulation mesh generation algorithm based on the three-dimensional model to obtain a new Delaunay triangulation mesh structure, and its rectangular structure is converted into a triangular structure. The main purpose is to lighten the data. Then, according to the Bowyer-Watson algorithm, a new node is added to the triangular mesh, and all triangles whose circumscribed circles contain the newly added node are found and deleted to form a cavity. The nodes of the cavity are connected with the newly added nodes to form a new Delaunay triangular mesh. The cycle continues until all points are traversed and the mesh structure is structured.

[0060] Step 4.2: Based on the spatial triangular mesh structure generated in the previous step, the order of mesh vertex loading is determined by vertex index and flood evolution order, and a linear relationship between water depth value and corresponding time of mesh vertex is established. Based on the order of mesh vertex loading, the vertex is assigned a color value, which is determined by the water depth value. The deeper the water depth value, the darker the color.

[0061] Step 4.3: Model display. The river flood evolution grid model with color values ​​generated in the previous step is integrated into the three-dimensional GIS engine Cesium for display through vertex indexing, and the animation effect is set in combination with the evolution time and water flow direction in the evolution calculation results, that is, the grid vertices and water depth values ​​at each moment are displayed in vertex time sequence, and finally a three-dimensional dynamic demonstration of floods in the Cesium three-dimensional scene is realized.

[0062] The above process describes a specific example and application method of the present invention. Technical developers in this field should understand that this example only studies a target area and provides an explanation. Technical developers in this field should be able to change and innovate the above model visualization algorithm without departing from the principle and essence of the present invention. For example, by applying the operating ideas of the above model visualization algorithm, further optimization can be performed based on the two-dimensional hydrodynamic model of the HEC-RAS software to further improve the display effect and rendering efficiency of the evolution model.

Claims

1. A method for dynamically displaying a river flood evolution grid model based on a Cesium three-dimensional scene, characterized in that: The method comprises the following steps: A. Cesium 3D scene geographic data preprocessing is used for Cesium 3D scene construction. The basic image of the study area is constructed by controlling, orienting, and correcting the image map DOM digital data generated by drone aerial photos, and the DEM data collected by laser radar is used to produce river terrain data, thereby constructing a virtual 3D scene of the study area; B. Pre-construction of river flood evolution grid model: using the two-dimensional hydrodynamic model of HEC-RAS software to construct an unstructured river flood evolution grid model; C. Conversion of calculation results of river flood evolution grid model, used for format conversion, into data format that can be recognized by Cesium 3D scene; D. Reconstruct the river flood evolution grid model, reprocess the initially established unstructured river flood evolution grid model and convert it into a structured river flood evolution grid model, so as to improve the loading efficiency while ensuring the visualization effect; E. Dynamic display of river flood evolution grid model. For the constructed river flood evolution grid model, the river flood evolution grid model is displayed in the Cesium three-dimensional scene according to the vertex order, depth and water level elements of this evolution model.

2. According to claim 1, a method for dynamically displaying a river flood evolution grid model based on a Cesium three-dimensional scene is characterized in that: The Cesium 3D scene geographic data preprocessing refers to using the river DEM data and DOM digital data of the study area as the basic data for scene construction, and using ArcGIS software to eliminate data that does not conform to the study area, and converting the two into a data structure that can be rendered by Cesium through Cesiumlab, and displaying it as a virtual 3D scene in the Cesium 3D scene.

3. According to claim 1, a method for dynamically displaying a river flood evolution grid model based on a Cesium three-dimensional scene is characterized in that: The pre-construction of the river flood evolution grid model means that first, DEM data is imported through the HEC-RAS software, and then grid and terrain interpolation are performed on it. Then, the measured flow data is used for the inflow boundary to perform unsteady flow analysis UnsteadyFlowAnalysis, and the normal water depth NormalDepth boundary condition provided by the HEC-RAS model is used for the outflow boundary. The water level is solved at the boundary by the steady flow equation, and the model operation parameters are set. The model operation parameters include the time step, the time interval of the flood evolution animation, the weight parameter and the calculation equation. Then, according to the set model operation parameters, the hydrodynamic model is run to calculate the water level, flow velocity and flow elements in the river system and the flood protection area.

4. According to claim 1, a method for dynamically displaying a river flood evolution grid model based on a Cesium three-dimensional scene is characterized in that: The water level and the flow rate are calculated based on the two-dimensional simplified form of the Navier-Stokes equation - the shallow water equation, and the flow rate is calculated based on the water-passing cross-sectional area and the average flow rate of the cross-sectional area.

5. According to claim 3, a method for dynamically displaying a river flood evolution grid model based on a Cesium three-dimensional scene is characterized in that: The conversion of the calculation results of the river flood evolution grid model refers to converting the unstructured river flood evolution grid model obtained by the HEC-RAS software, and using Python to further parse the obtained evolution model calculation results and convert them into a common JSON format.

6. According to claim 3, a method for dynamically displaying a river flood evolution grid model based on a Cesium three-dimensional scene is characterized in that: The reconstruction of the river flood evolution grid model refers to the structural gridding processing of the initially established unstructured river flood evolution grid model: dividing the grid by the Delaunay triangulation grid generation algorithm of the three-dimensional model and re-triangulating the grid vertices according to the Bowyer-Watson algorithm, converting its grid structure from unstructured to structured, establishing a linear relationship between the elevation value of the DEM data and the water level of the river flood evolution grid model, and storing it in the evolution model.

7. The method for dynamically displaying a river flood evolution grid model based on a Cesium three-dimensional scene according to claim 3 is characterized in that: The dynamic display module of the river flood evolution grid model assigns different color textures to the grid vertices of the reconstructed river flood evolution grid model according to the water level value, and the animation evolution effect of the river flood evolution grid model is displayed in the Cesium three-dimensional scene.

8. A computer-readable storage medium having computer instructions stored thereon, characterized in that: When the computer program instructions are executed by a processor, they are used to implement the steps of the method as described in any one of claims 1 to 7.

9. A computer program product comprising computer instructions, characterized in that When the computer instructions are executed by a processor, they are used to implement the steps of the method according to any one of claims 1 to 7.

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