Digital twin basin topographic image service fusion method

Abstract

The invention discloses a digital twin basin topographic image service fusion method. The method comprises the following steps: S1, planning map data according to the data precision and the construction range of geographic spatial data of the digital twin basin; s2, according to the precision and range planned in the S1, collecting and processing map data meeting the requirements of the digital twinborn basin; s3, formulating a map pyramid hierarchy loading strategy in different scenes of the digital twin basin; s4, performing tile fusion on the DOM data of the L1-level digital twinning, the L2-level digital twinning and the L3-level digital twinning; s5, making a tile fusion meta-file, and outputting a watershed digital twin image tile data set; s6, performing fusion slicing on the L1-level, L2-level and L3-level digital twinborn DEM data, and outputting a drainage basin digital twinborn terrain tile data set; and S7, publishing the digital twin basin image service and terrain service of the basin. The method has the advantage of realizing light weight of map data and services.

Description

Technical Field

[0001] The present invention belongs to the technical field of watershed digital twin applications, and specifically relates to a digital twin watershed terrain image service fusion method. Background Art

[0002] The application of digital twin technology in watershed management is to combine the concept of digital twin with watershed management, and to build a digital twin model that can highly realistically reflect the hydrological and environmental changes in the actual physical watershed by integrating key technologies such as geographic information system (GIS), building information model (BIM), Internet of Things technology, and water conservancy professional models. Such a model can provide scientific and accurate support and decision-making basis for business applications such as prevention of flood and drought disasters, optimal allocation of water resources, protection of water environment and ecological restoration, and disaster emergency response. The digital twin technology of the watershed is an innovative management method. By building a digital twin model, it can reproduce the complex hydrological and environmental changes of the real physical watershed with high fidelity. The implementation of this technology needs to rely on the support of key technologies such as GIS, BIM, Internet of Things, and water conservancy professional models. In the process of building a digital twin model of the watershed, in order to meet the high-precision requirements of digital twins for spatial data, spatial data are usually divided into different levels to create map scenes of different levels; these levels include L1, L2 and L3, each level corresponds to different regions and accuracy requirements; especially in the L3 level, the division of engineering 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 the characteristics of discontinuous geographical scope and discontinuous spatial scale accuracy. In order to cope with the geographical scope and accuracy requirements of different regions, it is usually necessary to divide the data into multiple different services. The traditional way to establish a map service is to perform pyramid tile processing of images and terrain for each region in each level separately, and publish the corresponding services. However, this approach will lead to the generation of 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 high-precision image tiles at a small scale in a macroscopic scene, there is actually only a small effective area in the macroscopic scene or mesoscopic scene (0 to 16 pyramid tiles), which not only affects the visualization effect, but also the image data of L1 or L2 precision is sufficient to meet the precision and visualization requirements of the digital twin at this level. Too many image and terrain tile services will also reduce the efficiency of data loading and occupy unnecessary storage resources; Therefore, it is necessary to develop a digital twin watershed terrain image service fusion method that can reduce the number of map services, simplify the maintenance and management process of spatial data services, and reduce the generation of redundant tile data. Summary of the invention

[0003] The purpose of the present invention is to provide a method for fusing terrain image services of a digital twin watershed, reduce the number of map services, simplify the maintenance and management process of spatial data services, reduce the generation of redundant tile data, and realize the lightweight of map data and services; the present invention plans L1, L2, and L3 map data that meet the digital twin standards, and formulates a loading strategy for the map pyramid level of the digital twin watershed in different scenarios; by tile fusion of DOM (digital orthophoto) data and fusion slicing of DEM (digital elevation model) data, a unified image tile service and a unified terrain tile service are finally released, thereby meeting the requirements and visualization effects of the digital twin of the entire watershed for map services; and solves the problem that the spatial data of the digital twin of the watershed is too detailed in accuracy and regional division, resulting in too many image and terrain pyramid tile services.

[0004] 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 at 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; 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.

[0005] 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, level L1 is the low-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 includes key business focus areas such as river basin flood control with DOM resolution better than 20 centimeters, L2 level includes important sections of major rivers and main tributaries, important lakes, national flood storage areas, and key areas of soil and water conservation with DOM resolution better than 1 meter and DEM grid size better than 15 meters; L3 level includes engineering management and protection scope with DOM resolution better than 1 meter and DEM grid size better than 5 meters, L3 level includes hydraulic construction / structures with DOM resolution better than 10 centimeters and DEM grid size better than 2 meters.

[0006] In the above technical solution, in S2, the map data that meets the requirements of digital twins includes data from different areas (land and underwater areas), different precisions (meter level, sub-meter level, centimeter level), and different data sources (satellite remote sensing, drone flight, unmanned ship); 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: In order to ensure the visualization effect of digital twin images, the collected DOM data is post-processed and the DOM result data is finally output; the post-processing methods of the collected DOM data include: uniform light and color, shadow removal of hydraulic structures, replacement of riverbed texture with water surface, mosaic and cropping, etc.; S2-3: In order to ensure the visualization effect of digital twin terrain, the collected DEM data is post-processed and finally the DEM result data is output; the methods for post-processing the collected DEM data include: removing residual noise, partial U-shaped excavation of the reservoir, smoothing the boundaries of terrain with different accuracies, mosaicking and cropping, etc.

[0007] In the above technical solution, in S3, different scenarios of the digital twin river basin include macro scenarios, meso scenarios, and micro scenarios; among them, the macro scenario mainly focuses on a larger area, with a range of 10 to 20 kilometers along the river basin, displaying geographic information at the national, provincial, and municipal levels; the meso scenario mainly focuses on key river basins or key focus areas, with a range of 500 to 1,000 meters along the river basin, displaying geographic information at the river basin level and regional level; the micro scenario mainly focuses on key building areas, with a range of 100 to 200 meters along the river basin, displaying geographic information at the management level and building level.

[0008] In the above technical solution, 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 global, national, and provincial areas; secondly, the L2 area is divided, which includes key focus areas; finally, the L3 area is divided, which includes important entity areas; S3-2, design a vertical loading strategy for the map pyramid; In order to meet the accuracy and visualization effect of digital twins, the overall map pyramid level is designed to be 21 levels. Levels 0-13 are macro scene loading levels, all of which are L1 regional tiles. Among them, levels 0-7 are global regional tiles, levels 8-10 are national regional tiles, and levels 11-13 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 area and L3 area tiles, and levels 20-21 are L3 area tiles. The present invention supports multi-level precision loading through a pyramid level loading strategy to meet the needs of different scenarios for multi-precision data.

[0009] In the above technical solution, 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 digital twins; specific areas refer to DOM data in the L1 / L2 / L3 area range; specific zoom levels refer to extracting tiles of several levels after slicing the DOM data in the L1 / L2 / L3 area; for example, the DOM in the L2 area is sliced ​​to get levels 0-19, which belongs to the mesoscopic scene loading level, and only tiles of levels 14-19 need to be obtained; the DOM in the L3 area is sliced ​​to get levels 0-21, and tiles of levels 17-21 need to be obtained; Tile merging specifies the tile range, level, and order to be merged, and stitches them into a complete tile image dataset.

[0010] In the above technical solution, the method for making tiles for DOM data includes: Determine the tile size, resolution and coordinate system according to requirements, use professional map tile cutting tools or software to cut the geospatial data according to predetermined specifications, generate multiple tiles, and store the cut tiles on disk or in a database according to a certain directory structure.

[0011] In the above technical solution, the tile results finally generated by DOM data tile production include global level 0-7 tiles, national level 0-10 tiles, provincial level 0-13 tiles, L2 area level 0-19 tiles, L3 area level 0-21 tiles and the corresponding tilemapresource.xml tile fusion metadata file.

[0012] In the above technical solution, the process of extracting tiles from DOM data includes: Based on the tile results produced above, global level 0-7 tiles, national level 8-10 tiles, provincial level 11-13 tiles, L2 area level 14-19 tiles, and L3 area level 17-21 tiles are extracted respectively.

[0013] In the above technical solution, the method for performing tile fusion on DOM data includes: 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.

[0014] In the above technical solution, in S5, the method of preparing 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 title and projection mode (for example, EPSG:3857; other data can also be selected according to usage); S5-2: Set the bounding box of the map to the global range, covering the complete area of ​​the Web Mercator projection, 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; the present invention is more critical to set a unified origin to achieve tile fusion and prevent tile loading failure; row and column number naming and loading calculation are calculated based on the origin, and the origins and other information of different DOM separate slices of L1 / L2 / L3 are different. By setting a unified origin, range box and other information, a service is published; S5-3: Define the size of the tile (e.g. 256x256 pixels, or other pixels depending on the usage), and set the resolution and order of each level to cover 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.

[0015] In the above technical solution, 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 data set 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, tile format, etc.; use the tool to fuse the 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.

[0016] In the above technical solution, in S7, the method for outputting the digital twin watershed image service and terrain service includes: 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.

[0017] The beneficial effects of the present invention are as follows: (1) Through the fusion processing of image and terrain data (wherein, DOM service fusion is realized through steps S4 and S5, and DEM fusion is realized 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; the problem that the existing traditional map service establishment method is to perform pyramid tile processing of images and terrain for each area in each level separately and publish corresponding services, resulting in a large number of image and terrain services, thereby making the maintenance and management of spatial data services extremely difficult is solved; (2) The present invention optimizes the data loading process into a data service by adopting the data tile fusion method through steps S4, S5, and S6, thereby optimizing the data loading process, reducing the generation of redundant tile data, improving the efficiency of data loading, and saving storage resources; and 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, too many image and terrain tile services will reduce the efficiency of data loading, and occupy unnecessary storage resources, affecting the loading efficiency and causing computer freezes; (3) Optimizing service performance; the present invention adopts a centralized data and service publishing mechanism, and provides the fused elevation and image data to users as a single service, which effectively reduces the server's operating load, 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 that the existing technology needs to collect and process a large amount of image and terrain data. These spatial data have the characteristics of discontinuous geographical range and discontinuous spatial scale accuracy. In order to meet the geographical range and accuracy requirements of different regions, it is usually necessary to divide the data into multiple different services, that is, different regions and different accuracy DOMs publish their own image map services, and to publish data at levels 0-21, it is necessary to publish the DOM and DEM of many services, resulting in reduced data loading efficiency, greatly increasing the response time, and reducing the robustness and applicability of the system; (4) The present invention integrates services by merging data tiles, merging different data of multiple regions with multiple precisions into one service. The dom (digital orthophoto) merges tiles of different precisions in different regions of L3 / L2 (L2 / L3 regions are smaller but have higher precision) into corresponding pyramid-level tiles corresponding to the L1 level (larger range but lower precision); the dem (digital elevation model) merges and slices dems of different precisions and regions, and finally realizes that dom and dem each have only one service. This meets the requirements and visualization effects of the digital twin of the entire watershed for map services and solves the problem of the existing technology in realizing map services. The requirements and visualization effects of map services require the release of many service DOMs and DEMs, which generates a large amount of redundant tile data (the existing technology generally uses different regions and different precision DOMs to release their own image map services, such as: Region A releases L3 services at level L3 and 0.1 meters, Region B releases L3 services at level L3 and 0.1 meters, Region C releases L2 services at level L3 and 0.2 meters, and so on. The digital twin of the watershed has many regions and levels of DOMs and DEMs). This not only affects the visualization effects of map services, but too many image and terrain tile services will reduce the efficiency of data loading and occupy unnecessary storage resources. (5) The map data and services in the publishing service are lightweight, making the construction of the digital twin watershed model more efficient and solving the problem that too many map layers will affect efficiency. The final published unified image tile service and unified terrain tile service meet the requirements and visualization effects of the digital twin of the entire watershed for map services, providing more intuitive, accurate and effective support for watershed management (such as flood and drought prevention, optimal utilization of water resources, water environment protection and ecological restoration, disaster emergency response, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a general implementation flow chart of a digital twin watershed terrain image service fusion method of the present invention; Figure 2 The flowchart of the present invention is to perform tile fusion on the DOM data and output a watershed digital twin image tile dataset. DETAILED DESCRIPTION

[0019] The following is a detailed description of the implementation of the present invention in conjunction with the accompanying drawings, but they do not constitute a limitation of the present invention and are only given as examples. At the same time, the advantages of the present invention are made clearer and easier to understand through the description.

[0020] Referring to the attached drawings, it can be seen that the present invention discloses a method for fusion of digital twin watershed terrain image services, which aims to solve the problem of too many image and terrain pyramid tile services caused by too detailed spatial data accuracy and regional division in the existing watershed digital twin technology. The present invention includes the steps of map data planning, acquisition processing, map pyramid level loading strategy formulation, DOM and DEM data tile production, slice fusion and tile fusion metafile production for the three-level regions and precisions of the watershed digital twin L1, L2, and L3. According to different precisions and ranges, the digital twin watershed is multi-level modeled, and map data of different regions, precisions and data sources are processed through specific software tools to realize the fusion output of image and terrain services. The method realizes the tile fusion of DOM (digital orthophoto) data and the fusion slices of DEM (digital elevation model) data by planning L1, L2, and L3 map data that meet the digital twin standards, and formulating pyramid level loading strategies under different scenarios, thereby publishing unified image tile services and terrain tile services. The present invention systematically integrates map data of different sources, regions and precisions into a unified service by formulating accurate map data planning and hierarchical loading strategies, avoiding the complex operations of multiple loading and publishing of multiple map services, and improving data fusion efficiency. On the basis of meeting the requirements for the construction of the digital twin watershed data base, the present invention realizes lightweight processing of map data and services, significantly reduces the storage space occupied, and improves the map loading efficiency and management efficiency. By formulating pyramid-level loading strategies under different scenarios, the present invention can accurately display national, provincial, and municipal-level geographic information and detailed information of key watersheds or regions, and enhances the visualization effect of map services. With the further development of digital twin technology, the digital twin watershed terrain image service fusion method described in the present invention provides a unified geographic information basic map service for the watershed digital twin model, and will gradually become a core technical support means in the fields of flood and drought prevention, water resources optimization allocation, water environment protection and ecological restoration, laying a solid foundation for the intelligent and refined management of digital twin watersheds, and promoting watershed management to a higher level.

[0021] The present invention is dedicated to the field of watershed digital twins, and collects data according to relevant specifications. It is aimed at the tile fusion of watershed digital twin watershed map scenes, and can be relatively well applied to map scenes with dom and dem in related projects in the field of watershed digital twins; the present invention meets the scenarios with different spatial ranges and resolution requirements (that is, it is suitable for large-scale, multi-level geographic data management scenarios) through L1, L2, and L3 hierarchical data loading strategies, especially in the case of efficient loading of multi-regional and multi-scale map data, such as large-scale geographic analysis and resource management across watersheds; it solves the problems of unified integration, lightweight, data redundancy control, and accuracy and regional division optimization of map images and terrain services; the present invention simplifies the map tile management and service maintenance process in the watershed digital twin by reducing the number of map services, and is suitable for watershed digital twin systems that require long-term operation and maintenance and low-cost operation, and is suitable for the operation and maintenance and management scenarios of efficient map services, meeting the map service needs of different scenarios (such as simulation, visualization, and decision support) within the watershed.

[0022] The present invention has the following characteristics: (1) Support for all data types: The present invention covers digital orthophotos (DOM) and digital elevation models (DEM), supports the comprehensive integration 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 to meet the multi-scenario requirements of digital twin watersheds, while optimizing accuracy and performance; (3) Lightweight design: The present invention reduces the number of redundant tile data and services through data fusion and service unification, thereby achieving system lightweight and efficient maintenance; (4) Designed specifically for watershed digital twins: The present invention clearly targets the requirements of digital twin systems, solves the problem of overly detailed division of watershed spatial data, and optimizes service structure and data management; (5) Solve the redundancy problem: The present invention uses tile fusion metafiles and Slicing technology effectively controls data redundancy, reduces resource consumption and maintenance costs; (6) Strong watershed adaptability: The present invention provides unified image tile services and terrain tile services to ensure the visualization and consistency of the overall watershed system; it overcomes the problems of data type limitations in the prior art, lack of multi-level precision support, inability to meet the scenarios with different precision requirements in the watershed digital twin system, inability to reduce redundant tiles and optimize the number of services, and inability to achieve lightweight in large-scale distributed map services. At the same time, it overcomes the problems of the prior art that the single focus on privacy and security, the narrow target range, the inability to achieve lightweight, fusion, precision planning and other requirements of map data, the lack of unified support for image and terrain data, the existence of functional limitations, and the inability to achieve global map data integration or watershed digital twin scenario requirements.

[0023] Embodiment: The present invention is now described in detail by taking the application of the present invention to a certain region for fusion of digital twin watershed terrain image services as an embodiment, which also has a guiding role in the application of the present invention to other regions for fusion of digital twin watershed terrain image services.

[0024] In this embodiment, a certain area includes a macro scene, a meso scene, and a micro scene: 1) The overall background scene is constructed with L1 spatial data (the scope is 40 kilometers along the project line, DOM with 5m spatial resolution accuracy superimposed on DEM with 12.5m spatial resolution accuracy); 2) The mesoscopic scene uses L2 spatial data (the range is 10km along the project and 500 meters on both sides, using DOM with 0.8m spatial resolution and DEM with 5m spatial resolution) to construct the overall mesoscopic scene; 3) According to the characteristics of the project and the route, 22 L3 spatial data with a total area of ​​about 106.61 km² were selected as key areas for the micro-scene (the scope includes hydraulic structures, project management and protection scope, and a 200-meter range on both sides of the project, using 0.1 spatial resolution accuracy DOM superimposed with 0.5-meter spatial resolution accuracy DEM) to construct the overall micro-background scene; If image and terrain services are published normally according to the traditional map service establishment method, it is necessary to publish 1 L1, 44 L2 (22 images, 22 terrains), and 44 L3 (22 images, 22 terrains), a total of 89 services. The existence of multiple data services means that different data sources need to be managed and processed, which increases the complexity of the system, especially during data integration and analysis. Publishing multiple services at the same time may increase the server load and affect data access speed and response time, especially in high concurrency situations. When users access and use data of different scales, they may need to switch between multiple platforms or services, which increases the difficulty and time cost of use; data of different scales may be redundant, resulting in waste of storage and management.

[0025] like Figure 1 As shown, this embodiment adopts the method of the present invention to fuse the digital twin watershed terrain image data service, and the implementation steps include: 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; 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.

[0026] In the step S1, the area and accuracy corresponding to the L1, L2, and L3 DOM and DEM data of the watershed digital twin are planned, and the planned vector range data is output; In step S2, collecting and processing map data that meets the requirements of the digital twin watershed includes the following specific steps: According to the vector range data of the output plan, L1, L2, L3 DOM and DEM data of corresponding areas and precisions are collected to construct the original basic geographic information map data; In order to ensure the visualization effect of digital twin images, the collected DOM data is post-processed: uniform light and color, removal of hydraulic structure shadows, replacement of riverbed texture with water surface, mosaicking and cropping, etc., and finally the DOM result data is output; In order to ensure the visualization effect of digital twin terrain, the collected DEM data is post-processed: removing residual noise, U-shaped excavation of the reservoir, smoothing, mosaicking and clipping of terrain boundaries with different precisions, etc., and finally outputting DEM result data; like Figure 2 As shown, the main process of performing tile fusion on the DOM result data in step S4 specifically includes the following steps: Pyramid tiles are produced for the DOM achievement data of level L1 (global, national, provincial), level L2 (key focus area), and level L3 (important entity area) in turn. The pyramid slice levels are: L1 global level 7, L1 national level 10, L1 provincial level 13, L2 key focus area level 19, and L3 important entity area level 21; Run Cesiumlab data processing software, enter the image slicing tool, and select the DOM data to be sliced; Set the image parameters: spatial reference is EPSG3857, background transparency is band 4; processing parameters: service type is TMS format, projection parameter is Mercator projection, tile size is 256), other parameters remain default, output the file path, and submit for tile production; From the tile results generated above, in accordance with the requirements of the digital twin scene of the watershed for accuracy and visualization, based on the formulated map pyramid level loading strategy in different scenarios of the digital twin watershed, the tile data of the corresponding levels are extracted: L1 global 0-7 level tiles, L1 national 8-10 level tiles, L1 provincial 11-13 level tiles, L2 key focus area 14-19 level tiles, L3 important entity area 17-21 level tiles; Use image processing tools to search and remove tiles with zero pixel transparency to avoid white edges when loading maps in Unreal Engine. Create an image fusion service folder, and input the global, national, provincial, L2, and L3 tile data into the image fusion service folder in order from low to high levels; If tiles are repeated in the overlapping area at the same level of the pyramid, they will be covered based on the principle of replacing low-precision tiles with high-precision tiles. Finally, pyramid image tile data with different data sources, different precisions, and different regions will be constructed. The pyramid levels are 0-21. 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 folders to form the fused digital twin image tile dataset; Modify the pyramid metadata file and set the bounding box to the global range. The parameters are <boundingbox miny="-2.00387e+07" minx="-2.00375e+07" maxy="2.00387e+07" maxx="2.00375e+07" / > ; Define the map origin, the parameters are <origin y="-2.00387e+07" x="-2.00375e+07" / > ; Set the pyramid tile dataset and define the map projection mode as Web Mercator projection. The parameters are<TileSetsprofile="global-mercator"> ; Define the tile resolution and order of each level, for example, the parameters for level 0 are <tileset units-per-pixel="156543" order="0" / > , where the order parameter is set in the order of 0-21, and the units-per-pixel parameter is [156543,...,156543 / 2 order , 0.0746455]; After completing the above operations, the DEM result data will be merged and sliced; The main process of merging and slicing DEM results data includes the following steps: Run Cesiumlab data processing software, click Data Processing-Terrain Slicing, and enter the Terrain Slicing Tool; Click the Add button, and a dialog box for selecting a file will pop up. Select the DEM data to be sliced. You must follow the principle of selecting from high to low precision, and select the L3, L2, and L1 DEM data to add in turn, ensuring that the L3, L2, and L1 terrain layers are arranged in order from low to high. Set terrain parameters, including spatial reference to EPSG3857, maximum level to automatic calculation, and other parameters to default; Set the processing parameters and specify the processing triangulation algorithm as CTB; Set the output file, specify the storage type as hash, determine the output path for tile storage, and finally click Submit to complete the fusion and slicing of multi-precision and multi-region DEM data at the same time, and output the fused digital twin terrain tile dataset; 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; The client only needs to load and request a digital twin image service and a digital twin terrain service to build a digital twin basic map scene for the entire river basin, reproducing the complex hydrological and environmental changes of the real physical river basin with high fidelity.

[0027] Conclusion: This embodiment adopts the method of the present invention, by integrating DOM and DEM data services of different regions, different resolutions and different scales, simplifies the data management process, improves data consistency and service performance, reduces storage redundancy, optimizes user experience and data update efficiency, and enhances data availability and analysis capabilities. Its centralized service mode significantly improves the efficiency and reliability of the system, provides strong support for the application of watershed digital twins, and has extremely high practical value.

[0028] Other parts not described belong to the prior art.

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; 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 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 a vertical loading strategy for the map pyramid; The overall map pyramid level is designed to be 21 levels. Levels 0-13 are macro scene loading levels, all of which are L1 regional tiles. Levels 0-7 are global regional tiles, levels 8-10 are national regional tiles, and levels 11-13 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 area and L3 area tiles, and levels 20-21 are L3 area tiles.

6. The digital twin watershed terrain image service fusion method according to claim 5 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.

7. The digital twin watershed terrain image service fusion method according to claim 6 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.

8. The digital twin watershed terrain image service fusion method according to claim 7 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 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.

9. The digital twin watershed terrain image service fusion method according to claim 8, characterized in that: 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.

10. The digital twin watershed terrain image service fusion method according to claim 9, 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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