A Digital Twin Basin Topographic Image Service Fusion Method

Abstract

The present invention discloses a method for fusing digital twin watershed terrain image services. It includes the following steps: S1, planning map data according to the data accuracy and construction scope of digital twin watershed geospatial data; S2, collecting and processing map data that meets the requirements of digital twin watersheds according to the accuracy and scope planned in S1; S3, formulating map pyramid level loading strategies for different scenarios of digital twin watersheds; S4, performing tile fusion on DOM data of L1, L2, and L3 levels of digital twins; S5, producing a tile fusion meta-file and outputting a watershed digital twin image tile data set; S6, performing fusion slicing on DEM data of L1, L2, and L3 levels of digital twins and outputting a watershed digital twin terrain tile data set; S7, publishing watershed digital twin watershed image services and terrain services. The present invention has the advantage of realizing the lightweight of map data and services.

Description

Technical Field

[0001] The present invention belongs to the technical field of digital twin applications in river basins, and particularly relates to a method for integrating digital twin river basin terrain image services. Background Art

[0002] The application of digital twin technology in river basin management combines the concept of digital twin with river basin management. By integrating key technologies such as geographic information system (GIS), building information model (BIM), Internet of Things technology, and water conservancy professional models, a digital twin model is constructed that can highly realistically reflect the hydrological and environmental changes in the actual physical river basin. Such a model can provide scientific and accurate support and decision-making basis for various business applications such as flood and drought disaster prevention, optimal allocation of water resources, protection and ecological restoration of water environment, and disaster emergency response.

[0003] River basin digital twin technology is an innovative management method that can reproduce the complex hydrological and environmental changes of the real physical river basin with high fidelity by constructing a digital twin model. The implementation of this technology relies on the support of key technologies such as GIS, BIM, Internet of Things, and water conservancy professional models. In the process of constructing a river basin digital twin model, in order to meet the high-precision requirements of digital twin for spatial data, spatial data is usually divided into different levels to create different levels of map scenes. These levels include L1, L2, and L3, and each level corresponds to different regions and precision requirements. Especially at the L3 level, the division of the project management and protection scope needs to be more detailed, which leads to the need to collect and process a large amount of image and terrain data. These spatial data have characteristics such as discontinuous geographical scope and discontinuous spatial scale precision. In order to cope with the geographical scope and precision requirements of different regions, data is usually divided into multiple different services. The traditional way of establishing map services is to separately perform pyramid tile processing of images and terrain for each region at each level and publish the corresponding services. However, this approach will result in a large number of image and terrain services, making the maintenance and management of spatial data services extremely difficult. In addition, in different application scenarios, if pyramid image tiles of different precisions are uniformly loaded, a large amount of redundant tile data will be generated. For example, when loading L3-level high-precision image tiles at a small scale in a macroscopic scenario, in the macroscopic scenario or medium-scale scenario (0 to 16-level pyramid tiles), there is actually only a very small effective area, which not only affects the visualization effect, but also the image data of L1 or L2 level precision is sufficient to meet the precision and visualization requirements of digital twin at this level. Too many image and terrain tile services will also reduce the data loading efficiency and occupy unnecessary storage resources.

[0004] Therefore, it is necessary to develop a digital twin watershed terrain image service fusion method that reduces the number of map services, simplifies the maintenance and management process of spatial data services, and reduces the generation of redundant tile data. Summary of the Invention

[0005] The purpose of the present invention is to provide a digital twin watershed terrain image service fusion method, which reduces the number of map services, simplifies the maintenance and management process of spatial data services, reduces the generation of redundant tile data, and realizes the lightweight of map data and services; the present invention plans map data at L1 level, L2 level, and L3 level that meet the digital twin standard, and formulates the loading strategy of map pyramid levels in different scenarios of the digital twin watershed; through tile fusion of DOM (Digital Orthophoto Map) data and fusion slicing of DEM (Digital Elevation Model) data, finally release a unified image tile service and a unified terrain tile service, so as to meet the requirements and visualization effects of the entire watershed digital twin for map services; solves the problem that the spatial data of the watershed digital twin is too detailed in terms of accuracy and regional division, resulting in too many image and terrain pyramid tile services.

[0006] In order to achieve the above purpose, the technical solution of the present invention is: a digital twin watershed terrain image service fusion method, which performs service fusion from the data level.

[0007] The specific method includes the following steps.

[0008] S1, plan map data according to the data accuracy and construction scope of the digital twin watershed geospatial data.

[0009] S2, collect and process map data that meets the requirements of the digital twin watershed according to the accuracy and scope planned in S1.

[0010] S3, formulate the loading strategy of map pyramid levels in different scenarios of the digital twin watershed.

[0011] S4, perform tile fusion on the DOM data of L1 level, L2 level, and L3 level digital twins.

[0012] S5, make a tile fusion meta-file and output the digital twin image tile dataset of the watershed.

[0013] S6, perform fusion slicing on the DEM data of L1 level, L2 level, and L3 level digital twins and output the digital twin terrain tile dataset of the watershed.

[0014] S7, publish the digital twin watershed image service and terrain service.

[0015] In the above technical solution, in S1, the data accuracy and construction scope of the digital twin basin geospatial data are divided into three levels: L1, L2, and L3; among them, L1 level is for low-precision surface modeling in the digital twin basin; L2 level is for fine modeling of key areas in the digital twin basin; L3 level is for modeling of important entity scenes in the digital twin basin.

[0016] In S1, the map data in the digital twin basin geospatial data includes DOM data and DEM data; among them, DOM data is a digital orthophoto image, which is used to provide geographical information and image information of the map; DEM data is a digital elevation model, which is used to provide elevation information and terrain features of the map.

[0017] The planned map data includes the specific scope and data accuracy of DOM and DEM corresponding to L1, L2, and L3 levels respectively; among them, L1 level is the national land area, the DOM resolution is better than 2 meters, and the DEM grid size is better than 30 meters; in L2 level, the DOM resolution of key areas such as basin flood control and other key operations is better than 20 centimeters, and in L2 level, the DOM resolution of important river reaches of large rivers and main tributaries, important lakes, national flood detention areas, and key soil and water conservation areas is better than 1 meter, and the DEM grid size is better than 15 meters; in L3 level, the DOM resolution of the project management and protection scope is better than 1 meter, and the DEM grid size is better than 5 meters, and in L3 level, the DOM resolution of hydraulic structures / buildings is better than 10 centimeters, and the DEM grid size is better than 2 meters.

[0018] In the above technical solution, in S2, the map data collected and processed to meet the requirements of digital twins includes data of different regions (land and underwater regions), different accuracies (meter level, sub-meter level, centimeter level), and different data sources (satellite remote sensing, UAV flight, unmanned ship).

[0019] The steps for collecting and processing map data to meet the requirements of the digital twin basin are as follows:

[0020] S2-1: According to the output planned vector range data, collect L1, L2, and L3 level DOM and DEM data of the corresponding regions and accuracies respectively, and construct the original basic geographic information map data.

[0021] S2-2: In order to ensure the visualization effect of the digital twin image, post-process the collected DOM data, and finally output the DOM result data; the methods for post-processing the collected DOM data include: equalization of illumination and color, removal of shadows of hydraulic structures, replacement of the water surface part with river bottom texture, mosaicking and cropping, etc.

[0022] S2-3: To ensure the visualization effect of the digital twin terrain, post-process the collected DEM data and finally output the DEM result data. The methods for post-processing the collected DEM data include: removing residual noise, U-shaped excavation of the reservoir part, smoothing the terrain boundaries with different precisions, mosaicking, and cropping, etc.

[0023] In the above technical solution, in S3, different scenarios of the digital twin basin include macro scenarios, meso scenarios, and micro scenarios. Among them, the macro scenario mainly focuses on a relatively large area, with a range of 10 kilometers to 20 kilometers extended outward along the basin, showing geographical information at the national, provincial, and municipal levels; the meso scenario mainly focuses on key basins or key areas of concern, with a range of 500 meters to 1000 meters extended outward along the basin, showing geographical information at the basin level and regional level; the micro scenario mainly focuses on key building areas, with a range of 100 meters to 200 meters extended outward along the basin, showing geographical information at the management level and building level.

[0024] In the above technical solution, in S3, the process of formulating the map pyramid level loading strategy for different scenarios of the digital twin basin includes the following steps:

[0025] S3-1, design the horizontal loading strategy of the map pyramid;

[0026] First, divide the L1-level area, which includes the global, national, and provincial levels; second, divide the L2 area, which includes areas such as key areas of concern; finally, divide the L3 area, which includes important entity areas.

[0027] S3-2, design the vertical loading strategy of the map pyramid;

[0028] To meet the digital twin accuracy and visualization effect, design the overall map pyramid level to be 21 levels. Levels 0-13 are the loading levels for the macro scenario, all of which are L1 area tiles. Among them, levels 0-7 are the tiles of the global area, levels 8-10 are the tiles of the national area, and levels 11-13 are the tiles of the provincial area;

[0029] Levels 14-18 are the loading levels for the meso scenario. Among them, levels 14-16 are L2 area tiles, and levels 17-18 include L2 area and L3 area tiles;

[0030] Levels 19-21 are the loading levels for the micro scenario. Among them, level 19 includes L2 area and L3 area tiles, and levels 20-21 are L3 area tiles. Through the pyramid level loading strategy of the present invention, it realizes the support for multi-level precision loading and meets the needs of different scenarios for multi-precision data.

[0031] In the above technical solution, in S4, the tile fusion of DOM data for L1-level, L2-level, and L3-level digital twins includes tile production, tile extraction, and tile merging of the DOM data;

[0032] Among them, tile production is used to generate image pyramid-level tiles in the TMS format. By specifying the resolution of the original DOM and the tile level, tiles with different zoom ratios are generated so that the corresponding tiles can be loaded at different magnification levels;

[0033] Tile extraction is used to extract tiles for specific regions and specific zoom levels of the digital twin; the specific region refers to the DOM data within the L1 / L2 / L3 region range; the specific zoom level refers to several levels of tiles extracted after slicing the DOM data in the L1 / L2 / L3 region; for example, the DOM in the L2 region is sliced to obtain levels 0-19, which belongs to the mesoscopic scene loading level, and only tiles at levels 14-19 need to be obtained; the DOM in the L3 region is sliced to obtain levels 0-21, and tiles at levels 17-21 need to be obtained;

[0034] Tile merging stitches them into a whole tile image dataset by specifying the tile range, level, and order to be merged.

[0035] In the above technical solution, the method for tile production of DOM data includes:

[0036] Determine the size, resolution, and coordinate system of the tiles according to requirements, and use professional map tile cutting tools or software to cut the geospatial data according to the predetermined specifications to generate multiple tiles, and store the cut tiles in a disk or database according to a certain directory structure.

[0037] In the above technical solution, the final tile results generated by the tile production of DOM data include global tiles at levels 0-7, national tiles at levels 0-10, provincial tiles at levels 0-13, L2-region tiles at levels 0-19, L3-region tiles at levels 0-21, and the corresponding tilemapresource.xml tile fusion metadata files.

[0038] In the above technical solution, the process of tile extraction of DOM data includes:

[0039] Based on the above-generated tile results, extract global tiles at levels 0-7, national tiles at levels 8-10, provincial tiles at levels 11-13, L2-region tiles at levels 14-19, and L3-region tiles at levels 17-21 respectively.

[0040] In the above technical solution, the method for tile fusion of DOM data includes:

[0041] Create an image fusion service folder. Extract the processed results from the tiles in the order from low level to high level. Input the tile data of the globe, the whole country, provinces, L2 regions, and L3 regions into the image fusion service folder respectively. If there are duplicate tiles in the overlapping area at the same pyramid level, ensure that the high-precision tiles replace the low-precision tiles. Finally, construct the pyramid image tile data that integrates different data sources, different precisions, and different regions.

[0042] In the above technical solution, in S5, the method for making the tile fusion meta-file and outputting the basin digital twin image tile dataset includes:

[0043] S5-1: Define the root element of the tile fusion meta-file and set the basic meta-information of the map, including the title, projection method (e.g., EPSG:3857; other data can also be selected according to the usage).

[0044] S5-2: Set the bounding box of the map to the global scope, covering the entire area of the Web Mercator projection. Set the origin coordinates of the map at the lower left corner of the global Web Mercator projection to make the image tiles in any area have a unique origin, which serves as the basis for tile fusion. It is crucial to set a unified origin in the present invention to achieve tile fusion and prevent the failure of tile loading. The row and column numbers are named and calculated based on the origin. The origins of different DOMs such as L1 / L2 / L3 for individual slices are different. By setting unified information such as the origin and the bounding box, a service can be published.

[0045] S5-3: Define the size of the tiles (e.g., 256x256 pixels, other pixels can also be selected according to the usage), and set the resolution and order of each level to cover the tile data of all levels.

[0046] S5-4: Place the tile fusion metadata file and the tile folder of levels 0-21 in the same directory to jointly form the fused digital twin image tile dataset.

[0047] In the above technical solution, in S6, the method for fusing and slicing the DEM data of L1-level, L2-level, and L3-level digital twins and outputting the basin digital twin terrain tile dataset includes:

[0048] Import the DEM data of different precisions in the order of L3-level, L2-level, and L1-level respectively, and set the terrain slice generation parameters. The terrain slice generation parameters include the coordinate system, slice level, tile format, etc. Through the method of fusing and slicing with tools, according to the layer order of L3-level, L2-level, and L1-level, ensure that the high-precision data covers the low-precision sampled DEM data in the overlapping area, and construct the fused basin digital twin terrain tile dataset.

[0049] In the above technical solution, in S7, the method for outputting digital twin watershed image services and terrain services includes:

[0050] Place the fused digital twin image tile dataset and digital twin terrain tile dataset on the map server, configure the service address using the nginx server tool, map the service address to the image and terrain tile data folders for service publishing, and output the digital twin watershed image service and terrain service.

[0051] The beneficial effects of the present invention are as follows:

[0052] (1) Through the fusion processing of image and terrain data (wherein, the dom service fusion is achieved through steps s4 and s5, and the dem fusion is achieved through step S6), the number of map services is reduced, the maintenance and management process of spatial data services is simplified, and the maintenance cost is reduced; it solves the problem that the existing traditional method for establishing map services is to perform pyramid tile processing of images and terrains separately for each region at each level and publish the corresponding services, resulting in a large number of image and terrain services, making the maintenance and management of spatial data services extremely difficult.

[0053] (2) The present invention optimizes the data loading process into a single data service by adopting the method of data tile fusion in steps S4, S5, and S6, optimizes the data loading process, reduces the generation of redundant tile data, improves the data loading efficiency, and saves storage resources; it solves the problem that in different application scenarios, if pyramid image tiles of different precisions are uniformly loaded, a large amount of redundant tile data will be generated, and too many image and terrain tile services will reduce the data loading efficiency, occupy unnecessary storage resources, affect the loading efficiency, and cause the computer to freeze.

[0054] (3) Optimize service performance; the present invention adopts a centralized data and service publishing mechanism, provides the fused elevation and image data to users as single services respectively, effectively reduces the running load of the server, significantly reduces the response time, improves the efficiency of data query and transmission, and enhances the robustness and applicability of the system; it overcomes the problem in the prior art that a large amount of image and terrain data need to be collected and processed, and these spatial data have characteristics such as discontinuous geographical ranges and discontinuous spatial scale precisions. In order to meet the geographical range and precision requirements of different regions, the data usually needs to be divided into multiple different services, that is, different regions and different precision doms publish their respective image map services, and the data is published at levels 0 - 21, requiring a large number of doms and dems to be published, resulting in a reduction in data loading efficiency, a significant increase in response time, and a decrease in the robustness and applicability of the system.

[0055] (4) The present invention performs service integration through data tile fusion, merging different data with multiple precisions and regions into one service. For DOM (Digital Orthophoto Map), tiles with different precisions in different regions of L3 / L2 (smaller regions but higher precision in L2 / L3) are merged into the corresponding pyramid-level tiles of L1 (larger range but lower precision); for DEM (Digital Elevation Model), DEM fusion slices with different precisions and regions are merged, ultimately enabling DOM and DEM to each have only one service; meeting the requirements of the digital twin of the entire basin for map services and visualization effects; solving the problem that the prior art needs to publish a large number of DOM and DEM services to meet the requirements of map services and visualization effects, generating a large amount of redundant tile data (in the prior art, generally, DOMs with different regions and precisions publish their respective image map services, for example: the L3 level with 0.1 meters in area A publishes an L3-level service, the L3 level with 0.1 meters in area B publishes an L3-level service, the L2 level with 0.2 meters in area C publishes an L2-level service, and so on. There are many regions and levels of DOM and DEM in the digital twin of the basin), which not only affects the visualization effect of map services, but also reduces the data loading efficiency due to excessive image and terrain tile services, and occupies unnecessary storage resources.

[0056] (5) It realizes the lightweight of map data and services in the published services, making the construction of the digital twin basin model more efficient, solving the problem that too many map layers will affect the efficiency, and enabling a unified image tile service and a unified terrain tile service finally published to meet the requirements of the digital twin of the entire basin for map services and visualization effects, providing more intuitive, accurate and effective support for basin management (such as business operations like flood and drought disaster prevention, optimal utilization of water resources, water environment protection and ecological restoration, and disaster emergency response). BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is the overall implementation flowchart of a method for integrating terrain image services of a digital twin basin of the present invention;

[0058] Figure 2 It is the flowchart for performing tile fusion on DOM data in the present invention and outputting a dataset of digital twin image tiles of the basin. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] The following will describe in detail the implementation of the present invention with reference to the accompanying drawings. However, they do not constitute a limitation to the present invention and are only for illustration purposes. At the same time, the advantages of the present invention will be made clearer and easier to understand through the description.

[0060] Referring to the attached drawings, it can be seen that the present invention discloses a method for fusing digital twin watershed terrain image services, aiming to solve the problem of excessive image and terrain pyramid tile services in existing watershed digital twin technologies due to the high precision of spatial data and overly detailed regional division. The present invention includes steps such as map data planning, acquisition and processing of the L1, L2, and L3 levels of regional and precision in the digital twin watershed, formulating map pyramid level loading strategies, producing DOM and DEM data tiles, slice fusion, and producing tile fusion meta-files. According to different precisions and ranges, multi-level modeling of the digital twin watershed is carried out, and map data of different regions, precisions, and data sources are processed through specific software tools to achieve the fusion output of image and terrain services. This method realizes the tile fusion of DOM (Digital Orthophoto Map) data and the fusion slicing of DEM (Digital Elevation Model) data by planning L1, L2, and L3 level map data that conform to digital twin standards and formulating pyramid level loading strategies for different scenarios, thereby publishing unified image tile services and terrain tile services. By formulating precise map data planning and hierarchical loading strategies, the present invention systematically fuses map data from different sources, regions, and precisions into a unified service, avoiding the complex operations of multiple loading and publishing of multiple map services, and improving the data fusion efficiency. On the basis of meeting the requirements for building the data floor of the digital twin watershed, the present invention realizes the lightweight processing of map data and services, significantly reducing the storage space occupancy, and improving the map loading efficiency and management efficiency. By formulating pyramid level loading strategies for different scenarios, the present invention can accurately display geographical information at the national, provincial, and municipal levels and detailed information of key watersheds or regions, enhancing the visualization effect of map services. With the further development of digital twin technology, the method for fusing digital twin watershed terrain image services described in the present invention provides a unified geographical information basic map service for the digital twin watershed model, and will gradually become the core technical support means in the fields of flood and drought disaster prevention, optimal allocation of water resources, water environment protection and ecological restoration, laying a solid foundation for the intelligent and refined management of the digital twin watershed, and promoting the watershed management to a higher level.

[0061] The present invention is specifically used in the field of digital twin of river basins. It collects data according to relevant specifications. For the tile fusion of the digital twin river basin map scene in the river basin, it can be well applied to the map scenes with DOM and DEM in related projects in the field of digital twin of river basins. Through the L1, L2, and L3 hierarchical data loading strategies, the present invention meets the scenarios with different spatial ranges and resolution requirements (i.e., it is applicable to large-scale and multi-level geographical data management scenarios). Especially in the case of needing to efficiently load multi-region and multi-scale map data, such as large-scale geographical analysis and resource management across river basins. It solves the problems of unified fusion, lightweighting, data redundancy control, and accuracy and regional division optimization of map images and terrain services. By reducing the number of map services, the present invention simplifies the map tile management and service maintenance processes in the digital twin of river basins, is suitable for the digital twin system of river basins that requires long-term operation and maintenance and low-cost operation, is applicable to the operation and maintenance and management scenarios of efficient map services, and meets the map service requirements of different scenarios (such as simulation, visualization, and decision support) within the river basin range.

[0062] The present invention has the following characteristics: (1) Support for all data types: The present invention covers digital orthophoto maps (DOM) and digital elevation models (DEM), supports the comprehensive fusion of images and terrain, and adapts to different data requirements; (2) Multi-level planning: The present invention formulates L1, L2, and L3 multi-level loading strategies, meets the multi-scenario requirements of the digital twin river basin, and optimizes accuracy and performance at the same time; (3) Lightweight design: Through data fusion and service unification, the present invention reduces redundant tile data and the number of services, achieving system lightweighting and efficient maintenance; (4) Specifically designed for the digital twin of river basins: The present invention clearly aims at the requirements of the digital twin system, solves the problem of overly detailed division of river basin spatial data, and optimizes the service structure and data management; (5) Solve the redundancy problem: Through the tile fusion meta-file and slicing technology, the present invention effectively controls data redundancy, reduces resource consumption and maintenance costs; (6) Strong adaptability to river basins: The present invention provides unified image tile services and terrain tile services, ensuring the visualization effect and consistency of the overall river basin system; It overcomes the problems existing in the prior art, such as data type limitations, lack of multi-level accuracy support, inability to meet the scenarios with different accuracy requirements in the digital twin system of river basins, inability to reduce redundant tiles and optimize the number of services, and inability to achieve lightweighting in large-scale distributed map services. At the same time, it overcomes the problems of the prior art that only targets privacy and security, has a narrow target range, cannot meet the requirements of lightweighting, fusion, and accuracy planning of map data, lacks unified support for image and terrain data, has functional limitations, and cannot achieve global map data integration or the requirements of the digital twin scenario of river basins.

[0063] Example: Now, taking the application of the present invention in a certain area for the integration of digital twin watershed topographic image services as an example, the present invention will be described in detail. The application of the present invention in other areas for the integration of digital twin watershed topographic image services also has guiding significance.

[0064] In this embodiment, a certain area includes a large-scale scene, a meso-scale scene, and a micro-scale scene:

[0065] 1) The large-scale scene constructs an overall background scene with L1-level spatial data (the range is 40 kilometers extended outward from both sides of the project line, and DOM with a spatial resolution accuracy of 5m is superimposed on DEM with a spatial resolution accuracy of 12.5m);

[0066] 2) The meso-scale scene constructs an overall meso-scale scene with L2-level spatial data (the range is 10 km along the project line and 500 meters extended outward on both sides, and DOM with a spatial resolution accuracy of 0.8m is superimposed on DEM with a spatial resolution accuracy of 5m);

[0067] 3) According to the characteristics of the project and along the line, 22 L3-level spatial data with a total area of about 106.61 km² are selected for the micro-scale scene (the range is the water conservancy buildings, the project management and protection scope, and 200 meters extended outward on both sides of the project line, and DOM with a spatial resolution accuracy of 0.1 is superimposed on DEM with a spatial resolution accuracy of 0.5m) as the key areas to construct the overall micro-scale background scene;

[0068] If the image and topographic services are normally published according to the traditional map service establishment method, 1 L1-level service, 44 L2-level services (22 images and 22 topographies), and 44 L3-level services (22 images and 22 topographies), a total of 89 services need to be published. The existence of multiple data services means that different data sources need to be managed and processed, increasing the complexity of the system, especially in data integration and analysis. At the same time, publishing multiple services may cause the server load to increase, affecting the data access speed and response time, especially in high-concurrency situations. When users access and use data at different scales, they may need to switch between multiple platforms or services, increasing the difficulty and time cost of use; there may be redundancy in data at different scales, resulting in waste of storage and management.

[0069] As Figure 1 shown, this embodiment uses the method of the present invention to integrate the digital twin watershed topographic image data service, and the implementation steps include:

[0070] S1. Plan the map data according to the data accuracy and construction scope of the digital twin watershed geographic spatial data;

[0071] S2. Collect and process the map data that meets the requirements of the digital twin watershed according to the accuracy and scope planned in S1;

[0072] S3. Develop the map pyramid level loading strategy for different scenarios of the digital twin watershed;

[0073] S4. Perform tile fusion on the DOM data of L1, L2, and L3 levels of the digital twin;

[0074] S5. Create a tile fusion metadata file and output the digital twin image tile dataset of the watershed;

[0075] S6. Perform fusion slicing on the DEM data of L1, L2, and L3 levels of the digital twin and output the digital twin terrain tile dataset of the watershed;

[0076] S7. Publish the digital twin watershed image service and terrain service.

[0077] In the step S1, plan the regions and accuracies corresponding to the DOM and DEM data of L1, L2, and L3 levels of the digital twin watershed, and output the planned vector range data;

[0078] In the step S2, the collection and processing of map data meeting the requirements of the digital twin watershed include the following specific steps:

[0079] According to the output planned vector range data, collect the DOM and DEM data of L1, L2, and L3 levels corresponding to the regions and accuracies respectively, and construct the original basic geographic information map data;

[0080] To ensure the visualization effect of the digital twin image, post-process the collected DOM data: equalize light and color, remove the shadows of hydraulic buildings, replace the water surface part with the river bottom texture, mosaic and clip, etc., and finally output the DOM result data;

[0081] To ensure the visualization effect of the digital twin terrain, post-process the collected DEM data: remove residual noise, U-shaped excavation of the reservoir part, smooth the terrain boundaries of different accuracies, mosaic and clip, etc., and finally output the DEM result data;

[0082] As Figure 2 shown, the main process of tile fusion of the DOM result data in the step S4 specifically includes the following steps:

[0083] Perform pyramid tile production on the DOM result data of L1 (global, national, provincial), L2 (key focus areas), and L3 (important entity areas) levels in sequence. The pyramid slice levels are: L1 global level 7, L1 national level 10, L1 provincial level 13, L2 key focus areas level 19, and L3 important entity areas level 21;

[0084] Run the Cesiumlab data processing software, enter the image slicing tool, and select the DOM data to be sliced;

[0085] Set image parameters: the spatial reference is EPSG3857, and the background transparency is the 4th band; processing parameters: the service type is in the TMS format, the projection parameter is the Mercator projection, and the tile size is 256), and other parameters remain default. After setting the output file path, submit for tile production;

[0086] From the generated tile results above, according to the requirements of the digital twin scenario of the basin for accuracy and visualization effects, based on the formulated map pyramid level loading strategy in different scenarios of the digital twin basin, extract the tile data of the corresponding levels: L1 global tiles of levels 0 - 7, L1 national tiles of levels 8 - 10, L1 provincial tiles of levels 11 - 13, L2 key focus area tiles of levels 14 - 19, L3 important entity area tiles of levels 17 - 21;

[0087] Use an image processing tool to search for and remove tiles with a pixel transparency of 0 to avoid white edge problems when loading the map in the Unreal Engine;

[0088] Create an image fusion service folder, and in the order from low level to high level, input the tile data of global, national, provincial, L2 level, and L3 level into the image fusion service folder in sequence;

[0089] If tiles are repeated in the overlapping area at the same level of the pyramid, then cover them according to the principle of replacing low-precision tiles with high-precision tiles. Finally, construct pyramid image tile data that integrates different data sources, different precisions, and different regions, with the pyramid levels ranging from 0 to 21;

[0090] Create a tile fusion metadata file (tilemapresource.xml) for the TMS service, and place it in the same directory as the 0 - 21 level tile folder, jointly constituting the fused digital twin image tile dataset;

[0091] In the pyramid metadata file, set the bounding box to the global scope, and the parameter is <boundingbox miny="-2.00387e+07" minx="-2.00375e+07" maxy="2.00387e+07" maxx="2.00375e+07" / > ;

[0092] Define the map origin, and the parameter is <origin y="-2.00387e+07" x="-2.00375e+07" / > ;

[0093] Set the pyramid tile dataset, define the map projection method as Web Mercator projection, and the parameter is <TileSetsprofile="global-mercator">; define the resolution and level order of each level of tiles. For example, the parameter for level 0 is <tileset units-per-pixel="156543" order="0" / > , where the parameter order is set in sequence from 0 to 21, and the parameter units-per-pixel are [156543,...,156543 / 2 order , 0.0746455];

[0094] After completing the above operations, next, perform fusion slicing on the DEM result data;

[0095] The main process of performing fusion slicing on the DEM result data specifically includes the following steps:

[0096] Run the Cesiumlab data processing software, click Data Processing - Terrain Slicing, and enter the terrain slicing tool;

[0097] Click the Add button, a file selection dialog box will pop up, select the DEM data to be sliced. It is necessary to select the L3-level, L2-level, and L1-level DEM data in sequence according to the selection principle from high precision to low precision, and ensure that the serial numbers of the L3-level, L2-level, and L1-level terrain layers are arranged from low to high;

[0098] Set the terrain parameters, mainly including the spatial reference as EPSG3857, the maximum level as automatically calculated, and other parameters as default;

[0099] Set the processing parameters, and specify the processing triangle algorithm as CTB;

[0100] Set the output file, specify the storage type as hash, determine the output path for storing the tiles, and finally click Submit for Processing to complete the fusion slicing of the DEM data with multiple precisions and multiple regions simultaneously, and output the fused digital twin terrain tile dataset;

[0101] Place the fused digital twin image tile dataset and the digital twin terrain tile dataset on the map server, use the nginx server tool to configure the service address, map the service address to the image and terrain tile data folders for service publishing, and output the digital twin basin image service and terrain service;

[0102] After the client only needs to load and request a digital twin image service and a digital twin terrain service, it can construct the entire basin digital twin basic map scene, and reproduce the complex hydrological and environmental changes of the real physical basin with high fidelity.

[0103] Conclusion: In this embodiment, the method of the present invention is adopted. By fusing DOM and DEM data services in different regions, different resolutions, and different scales, the data management process is simplified, the data consistency and service performance are improved, the storage redundancy is reduced, the user experience and data update efficiency are optimized, and the data availability and analysis ability are enhanced. Its centralized service method significantly improves the efficiency and reliability of the system, provides strong support for the application of the basin digital twin, and has extremely high practical value.

[0104] Other parts not described are all prior arts.

Claims

1. A digital twin watershed terrain image service fusion method, characterized by: Service integration from the data level, The specific method includes the following steps: S1, planning map data according to the data accuracy and construction scope of the digital twin basin geospatial data; S2, based on the accuracy and scope planned in S1, collects and processes map data that meets the requirements of the digital twin watershed; S3, formulate map pyramid level loading strategies in different scenarios of digital twin watershed; In S3, the process of formulating the map pyramid level loading strategy in different scenarios of the digital twin watershed includes the following steps: S3-1, design a map pyramid lateral loading strategy; First, the L1 level area is divided, which includes the global, national, and provincial areas; secondly, the L2 area is divided, which includes the key focus areas; finally, the L3 area is divided, which includes the important entity areas; S3-2, design the vertical loading strategy of the map pyramid; the overall map pyramid level is designed to be 21 levels, 0-13 levels are macro scene loading levels, all of which are L1 regional tiles, among which 0-7 levels are global regional tiles, 8-10 levels are national regional tiles, and 11-13 levels are provincial regional tiles; Levels 14-18 are mesoscopic scene loading levels, where levels 14-16 are L2 area tiles, and levels 17-18 include L2 and L3 area tiles; Levels 19-21 are micro-scene loading levels, where level 19 includes L2 and L3 area tiles, and levels 20-21 are L3 area tiles; S4, tile fusion of DOM data of L1, L2, and L3 digital twins; S5, making tile fusion metafile and outputting watershed digital twin image tile dataset; S6, fusing and slicing the DEM data of the L1, L2, and L3 digital twins, and outputting the watershed digital twin terrain tile dataset; S7, release the watershed digital twin watershed image service and terrain service.

2. The digital twin watershed terrain image service fusion method according to claim 1 is characterized by: In S1, the data accuracy and construction scope of the digital twin basin geospatial data are divided into three levels: L1, L2, and L3; among them, level L1 is the low- and medium-precision surface modeling of the digital twin basin; level L2 is the fine modeling of key areas of the digital twin basin; level L3 is the modeling of important entity scenes in the digital twin basin; In S1, the map data in the digital twin watershed geospatial data includes DOM data and DEM data; DOM data is a digital orthophoto, which is used to provide geographic information and image information of the map; DEM data is a digital elevation model, which is used to provide elevation information and terrain features of the map; The planning map data include L1, L2 and L3 levels, which correspond to the specific scope and data accuracy of DOM and DEM respectively; among them, L1 level is the national land area, with DOM resolution better than 2 meters and DEM grid size better than 30 meters; L2 level has DOM resolution better than 20 centimeters for key business focus areas, and L2 level has DOM resolution better than 1 meter for important sections of major rivers and main tributaries, important lakes, national flood storage areas, and key areas of soil and water conservation, and DEM grid size better than 15 meters; L3 level has DOM resolution better than 1 meter for engineering management and protection areas, and DEM grid size better than 5 meters, and L3 level has DOM resolution better than 10 centimeters for hydraulic engineering buildings / structures, and DEM grid size better than 2 meters.

3. The digital twin watershed terrain image service fusion method according to claim 1 or 2, characterized in that: In S2, map data that meets the requirements of digital twins is collected and processed, including data from different regions, different precisions, and different data sources; The acquisition and processing of map data that meets the requirements of the digital twin watershed includes the following specific steps: S2-1: According to the vector range data of the output plan, collect L1, L2, L3 DOM and DEM data of corresponding areas and precisions respectively, and construct the original basic geographic information map data; S2-2: post-process the collected DOM data and finally output DOM result data; The post-processing methods for the collected DOM data include: uniform light and color, shadow removal of hydraulic structures, replacement of riverbed texture with water surface, mosaicking and cropping; S2-3: Post-process the collected DEM data and finally output DEM result data; the methods for post-processing the collected DEM data include: removing residual noise, partial U-shaped excavation of the reservoir, smoothing the terrain boundaries of different precisions, mosaicking and clipping.

4. The digital twin watershed terrain image service fusion method according to claim 3 is characterized by: In S3, different scenarios of the digital twin river basin include macro scenarios, meso scenarios, and micro scenarios; among them, the macro scenario focuses on a larger geographical area, with a range of 10 to 20 kilometers along the river basin, and displays provincial and municipal-level geographic information; the meso scenario focuses on key river basins or key focus areas, with a range of 500 to 1,000 meters along the river basin, and displays river basin-level and regional-level geographic information; the micro scenario focuses on key building areas, with a range of 100 to 200 meters along the river basin, and displays management-level and building-level geographic information.

5. The digital twin watershed terrain image service fusion method according to claim 4 is characterized by: In S4, tile fusion of DOM data of L1, L2, and L3 digital twins includes tile production, tile extraction, and tile merging of DOM data; Among them, tile production is used to generate image pyramid level tiles in TMS format. By specifying the resolution and tile level of the original DOM, tiles with different scaling ratios are generated so that corresponding tiles can be loaded at different magnification levels. Tile extraction is used to extract tiles of specific areas and specific zoom levels of the digital twin; Tile merging specifies the tile range, level, and order to be merged, and stitches them into a complete tile image dataset.

6. The digital twin watershed terrain image service fusion method according to claim 5 is characterized by: The methods for tile creation of DOM data include: Determine the size, resolution and coordinate system of tiles according to requirements, use professional map tile cutting tools or software to cut geographic spatial data according to predetermined specifications, generate multiple tiles, and store the cut tiles to disk or database according to a certain directory structure; the final tile results generated by DOM data tile production include global 0-7 level tiles, national 0-10 level tiles, provincial 0-13 level tiles, L2 regional 0-19 level tiles, L3 regional 0-21 level tiles and corresponding tilemapresource.xml tile fusion metadata files; The process of tile extraction of DOM data includes: Based on the tile results produced above, we extract global 0-7 level tiles, national 8-10 level tiles, provincial 11-13 level tiles, L2 regional 14-19 level tiles, and L3 regional 17-21 level tiles respectively; The methods for tile fusion of DOM data include: Establish an image fusion service folder, and input the global, national, provincial, L2 regional, and L3 regional tile data into the image fusion service folder in order from low level to high level from the results of tile extraction and processing. If tiles are repeated in the overlapping area at the same level of the pyramid, ensure that high-precision tiles replace low-precision tiles, and finally construct pyramid image tile data that integrates different data sources, different precisions, and different regions.

7. The digital twin watershed terrain image service fusion method according to claim 6 is characterized by: In S5, the method of making a tile fusion metafile and outputting a watershed digital twin image tile dataset includes: S5-1: Define the root element of the tile fusion metafile and set the basic meta information of the map, including the title and projection mode; S5-2: Set the bounding box of the map to the global range, covering the complete area of ​​the Web Mercator projection, and set the origin coordinates of the map to the lower left corner of the global Web Mercator projection, so that image tiles in any area have a unique origin, which serves as the basis for tile fusion; S5-3: Define the size of the tile, and set the resolution and order of each level, covering the tile data of all levels; S5-4: The tile fusion metadata file and the 0-21 level tile folders are placed in the same directory, together forming the fused digital twin image tile dataset.

8. The digital twin watershed terrain image service fusion method according to claim 7 is characterized by: In S6, the method of fusing and slicing the DEM data of the L1, L2, and L3 digital twins and outputting the watershed digital twin terrain tile dataset includes: Import DEM data of different precisions in the order of L3, L2, and L1, and set the terrain slice generation parameters, including coordinate system, slice level, and tile format. Use tools to fuse slices in the order of L3, L2, and L1 layers to ensure high-precision coverage of low-precision sampled DEM data in overlapping areas, and construct a fused watershed digital twin terrain tile dataset.

9. The digital twin watershed terrain image service fusion method according to claim 8, characterized in that: In S7, the methods for outputting digital twin watershed image services and terrain services include: Put the fused digital twin image tile dataset and digital twin terrain tile dataset on the map server, use the nginx server tool to configure the service address, map the service address to the image and terrain tile data folder for service publishing, and output the digital twin watershed image service and terrain service.

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