Method and system for constructing a watershed terrain model based on multi-source elevation data

Abstract

This application relates to a method and system for constructing a watershed topographic model based on multi-source elevation data, comprising: preprocessing an oblique photogrammetry model by removing trees and hollowing out water areas; obtaining a core area ground elevation model using ground point cloud data extracted from the preprocessed oblique photogrammetry model; performing mosaic stitching and boundary zone transition fusion on the core area ground elevation model and a first elevation model to obtain a fused target watershed elevation model; spatially registering and fusion of the land and water area topographic model obtained based on a second elevation model and the preprocessed oblique photogrammetry model using a target rendering engine to obtain a fused core area topographic model; and cropping the fused core area topographic model and the fused target watershed elevation model using a target rendering engine to obtain a seamlessly fused target watershed topographic model.

Description

Technical Field

[0001] This application relates to the field of watershed digital twin geospatial data fusion technology, and in particular to a method and system for constructing watershed terrain models based on multi-source elevation data. Background Technology

[0002] A watershed digital twin is a 3D model constructed in digital space that is synchronized with and interacts with the physical watershed in real time, enabling the digital mapping and intelligent simulation of all elements of the target watershed. The target watershed includes a core area containing water bodies and an outer area surrounding the core area. The core area includes the underwater area at the bottom of the water body and the land area outside the water body.

[0003] In the process of constructing the geospatial data base of the digital twin of the target watershed, it is usually necessary to stitch and mosaic the high-precision core area oblique photogrammetry model, the low-precision target watershed elevation model, and the high-precision underwater topographic elevation model to generate the target watershed topographic model.

[0004] However, due to the different data sources and accuracy of these models, visual gaps exist at the junction when the core area oblique photogrammetry model is spliced ​​with the target watershed elevation model, and step-like protrusions exist at the junction when the underwater topographic elevation model is embedded into the water area of ​​the oblique photogrammetry model, thus making it impossible to generate a high-quality target watershed topographic model. Summary of the Invention

[0005] This application provides a method for constructing a watershed topographic model based on multi-source elevation data, which can achieve seamless integration of the target watershed elevation model, the underwater topographic elevation model and the core area oblique photogrammetry model, thereby generating a seamlessly integrated target watershed topographic model and obtaining a high-quality target watershed topographic model.

[0006] Firstly, this application provides a method for constructing a watershed topographic model based on multi-source elevation data, including:

[0007] The oblique photography model of the core area within the target watershed is preprocessed by removing trees and hollowing out water areas to obtain the preprocessed oblique photography model.

[0008] A ground elevation model of the core area is obtained by extracting ground point cloud data based on the preprocessed oblique photogrammetry model.

[0009] The ground elevation model of the core area and the first elevation model of the target watershed are mosaicked and the boundary zone transition is fused to obtain the fused elevation model of the target watershed.

[0010] Based on the second elevation model of the underwater topography of the water body area within the core area and the fused target watershed elevation model, a water-land area elevation map including the water body area and the water-land transition zone is obtained. The water-land area topography model generated based on the water-land area elevation map and the preprocessed oblique photogrammetry model are spatially registered and fused with the water-land connection through the target rendering engine to obtain the fused core area topography model.

[0011] The target watershed terrain model is obtained by cropping the elevation data of the core area of ​​the merged core area terrain model and the merged target watershed elevation model through the target rendering engine.

[0012] Secondly, this application provides a watershed terrain model construction system based on multi-source elevation data, including:

[0013] The preprocessing module is used to: perform tree removal and water area hollowing preprocessing on the acquired oblique photography model of the core area within the target watershed to obtain the preprocessed oblique photography model.

[0014] The extraction module is used to obtain a ground elevation model of the core area from ground point cloud data extracted based on the preprocessed oblique photogrammetry model.

[0015] The first fusion module is used to: mosaic and stitch together the ground elevation model of the core area and the first elevation model of the target watershed, and perform boundary zone transition fusion to obtain the fused elevation model of the target watershed.

[0016] The second fusion module is used to: obtain a water-land area elevation map including the water body area and the water-land transition zone based on the second elevation model of the underwater topography of the water body area within the core area and the fused target watershed elevation model; and perform spatial registration and water-land connection fusion of the water-land area topography model generated based on the water-land area elevation map and the preprocessed oblique photography model through the target rendering engine to obtain the fused core area topography model.

[0017] The trimming module is used to trim the elevation data of the core area of ​​the merged core area terrain model and the merged target watershed elevation model through the target rendering engine, so as to obtain the target watershed terrain model.

[0018] Thirdly, this application provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the watershed terrain model construction method based on multi-source elevation data provided in the first aspect.

[0019] Fourthly, this application provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, it implements the steps of the watershed terrain model construction method based on multi-source elevation data provided in the first aspect.

[0020] Fifthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the watershed terrain model construction method based on multi-source elevation data provided in the first aspect.

[0021] In this application, firstly, tree removal and water body hollowing are used to remove tree elevation data and water surface elevation data, making the preprocessed oblique photogrammetry model closer to the real terrain; ground point cloud extraction is used to obtain ground coordinate data and elevation data of the land area within the core area, resulting in a core area ground elevation model; the core area ground elevation model and the first elevation model are mosaicked; boundary zone transition fusion is used to smoothly transition the elevation data of the boundary zone between the core area and the outer area in the elevation model obtained after splicing the core area ground elevation model and the first elevation model from the elevation data of the core area ground elevation model to the elevation data of the first elevation model, resulting in a fused target watershed elevation model, enabling the core area ground elevation model and the first elevation model to be accurately fused, achieving seamless fusion of the core area ground elevation model and the first elevation model, thereby achieving seamless fusion of the oblique photogrammetry model and the first elevation model;

[0022] Secondly, by using the second elevation model of the underwater topography and the fused target watershed elevation model, a water-land area elevation map including the water body area and the water-land transition zone is obtained. The target rendering engine then spatially registers the water-land area topography model generated based on the water-land area elevation map with the preprocessed oblique photogrammetry model, accurately reproducing the positional relationship between the water-land area topography model and the preprocessed oblique photogrammetry model in the real world within a 3D virtual space. Finally, the target rendering engine performs water-land fusion, smoothly transitioning the elevation data of the water-land transition zone between the water body area and the land area in the spatially registered water-land area topography model and the preprocessed oblique photogrammetry model from the elevation data of the water-land area topography model to the elevation data of the preprocessed oblique photogrammetry model, resulting in a fused core area topography model. This allows for precise fusion of the water-land area topography model and the preprocessed oblique photogrammetry model, achieving seamless fusion of the water-land area topography model and the preprocessed oblique photogrammetry model, thereby achieving seamless fusion of the second elevation model and the preprocessed oblique photogrammetry model.

[0023] Thirdly, the elevation data of the target watershed elevation model located in the core area is cropped and fused by the target rendering engine. The elevation data of the fused core area terrain model is used as the elevation data of the core area of ​​the target watershed terrain model, and the elevation data of the fused target watershed elevation model located in the outer area is used as the elevation data of the outer area of ​​the target watershed terrain model. Based on the above-mentioned retained elevation data of the core area and the retained elevation data of the fused target watershed elevation model located in the outer area, the target watershed terrain model is obtained.

[0024] Therefore, the watershed topography model construction method based on multi-source elevation data provided in this application can achieve seamless integration of the target watershed elevation model (i.e., the first elevation model), the underwater topography elevation model (i.e., the second elevation model), and the core area oblique photography model (i.e., the oblique photography model) to construct a seamlessly integrated target watershed topography model, thereby generating a high-quality target watershed topography model. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0027] Figure 1 This is a schematic diagram of the first process of a watershed terrain model construction method based on multi-source elevation data provided in this application embodiment.

[0028] Figure 2 This is a schematic diagram of the second process of a watershed terrain model construction method based on multi-source elevation data provided in the embodiments of this application.

[0029] Figure 3 This is a 3D visual crack image formed by directly overlaying the oblique photogrammetry model with the first elevation model.

[0030] Figure 4 This is a 3D image of the water body surface in the oblique photography model.

[0031] Figure 5 A three-dimensional image of stepped protrusions formed after the second elevation model is inlaid into the water area of ​​the oblique photogrammetry model.

[0032] Figure 6This illustration shows the process of generating a textureless white film repair area by removing trees from the oblique photogrammetry model provided in this embodiment; wherein, Figure 6 Image 'a' is a 3D image of the oblique photogrammetry model before preprocessing. Figure 6 b is a 3D image of the cavity region formed by the oblique photography model. Figure 6 c represents a 3D diagram showing the connection skeleton formed by the hollow areas of the oblique photography model. Figure 6 d is a 3D image of the textureless white film repair area formed in the hollow area of ​​the oblique photography model.

[0033] Figure 7 This is a three-dimensional image obtained by superimposing the core area ground elevation model and the preprocessed oblique photogrammetry model provided in the embodiments of this application.

[0034] Figure 8 This is a three-dimensional view of the preliminary mosaic terrain elevation model provided in the embodiments of this application.

[0035] Figure 9 This is a three-dimensional diagram of the fused target watershed elevation model provided in the embodiments of this application.

[0036] Figure 10 This is a three-dimensional view of the water and land mosaic terrain model provided in the embodiments of this application.

[0037] Figure 11 This is a 3D view of the fused core area terrain model provided in the implementation of this application; wherein, Figure 11 a is a schematic diagram after geometric restoration. Figure 11 b is a schematic diagram showing the geometric repair and material assignment.

[0038] Figure 12 This is a three-dimensional diagram of the target watershed terrain model provided in the embodiments of this application.

[0039] Figure 13 This is a schematic diagram of the watershed terrain model construction system based on multi-source elevation data provided in the embodiments of this application.

[0040] Figure 14 This is a schematic diagram of the structure of the electronic device provided in the embodiments of this application. Detailed Implementation

[0041] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0042] Please see Figure 1and Figure 2 The watershed terrain model construction method based on multi-source elevation data provided in this application includes steps 100 to 500, which will be described in detail below.

[0043] Step 100: Perform tree removal and water area hollowing preprocessing on the obtained oblique photography model of the core area within the target watershed to obtain the preprocessed oblique photography model.

[0044] Step 200: Obtain the ground elevation model of the core area using the ground point cloud data extracted based on the preprocessed oblique photogrammetry model.

[0045] Step 300: The ground elevation model of the core area and the first elevation model of the target watershed are mosaicked and the boundary zone transition is fused to obtain the fused elevation model of the target watershed.

[0046] Step 400: Based on the second elevation model of the underwater topography of the water body area within the core area and the fused target watershed elevation model, a water-land area elevation map including the water body area and the water-land transition zone is obtained; the water-land area topography model generated based on the water-land area elevation map and the preprocessed oblique photogrammetry model are spatially registered and fused using a target rendering engine to obtain the fused core area topography model.

[0047] Step 500: Using the target rendering engine, the elevation data of the core area of ​​the merged core area terrain model and the merged target watershed elevation model are cropped to obtain the target watershed terrain model.

[0048] It should be noted that, in this application, the target watershed includes a core area and a peripheral area. The peripheral area refers to the area outside the core area within the target watershed. The core area includes a water body area and a land area. The topography of the core area includes the underwater topography corresponding to the water body area and the land topography corresponding to the land area. In this application, the elevation model refers to a digital elevation model. It should also be noted that, for the purpose of convenience, different expressions are used for the same object in this application. Specifically, the first elevation model and the target watershed elevation model refer to the same object; the second elevation model and the underwater topography elevation model refer to the same object; the oblique photography model and the core area oblique photography model refer to the same object.

[0049] In this embodiment, the oblique photography model, with its ability to accurately reproduce dams, dikes, hydraulic structures and coastal features, becomes a key data source for constructing core area scenes; the first elevation model is the core foundation for accurately describing the topographic features of the entire target watershed and supporting hydrological analysis and flood evolution simulation; the second elevation model can compensate for the lack of water surface and underwater topographic elevation data in the water body area.

[0050] It is understood that in the embodiments of this application, the oblique photogrammetry model, the first elevation model, and the second elevation model have different data sources and different data accuracies. For example, the oblique photogrammetry model is acquired through drone aerial photography, with a spatial resolution of 3 cm, and the elevation data uses the 1985 National Elevation Datum; the first elevation model is generated through aerospace topographic data collected by remote sensing satellites, with a spatial resolution of 12.5 meters, and the elevation data uses the WGS84 geodetic datum; the second elevation model is acquired through a shipborne multibeam echo sounder system, with a spatial resolution of 0.5 meters, and the elevation data uses the 1985 National Elevation Datum. It is understood that spatial resolution refers to the size of a pixel or grid in the planar direction. The size of the spatial resolution is equal to the pixel size and also equal to the grid size.

[0051] The spatial reference coordinate system of the oblique photogrammetry model is the CGCS2000 coordinate system, the spatial reference coordinate system of the first elevation model is the WGS84 coordinate system, and the spatial reference coordinate system of the second elevation model is the CGCS2000 coordinate system.

[0052] In this embodiment, the target rendering engine can be Unreal Engine (UE), such as UE4 or UE5. For example, the target rendering engine can be UE5.3.2.

[0053] Understandably, during the fusion of the oblique photogrammetry model of the core area and the first elevation model of the target watershed: on the one hand, the boundary of the oblique photogrammetry model of the core area contains a large number of non-surface features, resulting in an extremely irregular outline; on the other hand, the oblique photogrammetry model of the core area has high data accuracy while the first elevation model of the target watershed has low data accuracy. Therefore, directly superimposing the oblique photogrammetry model of the core area onto the first elevation model of the target watershed will create severe visual gaps. Please refer to [link / reference needed]. Figure 3 On the other hand, considering that water bodies in the oblique photography model may exhibit water surface breaks, please refer to [the relevant documentation / reference]. Figure 4 In cases where underwater topographic elevation data is missing, a newly acquired second elevation model of the underwater topography needs to be inlaid into the water area of ​​the oblique photogrammetry model. Because the source and accuracy of the land topographic data in the core area differ from the newly acquired underwater topographic data, there are differences in elevation. This results in an unnatural, stepped protrusion at the water-land interface when the second elevation model of the newly acquired underwater topography is inlaid into the water area of ​​the oblique photogrammetry model. Please refer to [link / reference needed]. Figure 5 .

[0054] In this embodiment, firstly, tree removal and water body hollowing are used to remove tree elevation data and water surface elevation data, making the preprocessed oblique photogrammetry model closer to the real terrain; ground point cloud extraction is used to obtain ground coordinate data and elevation data of the land area within the core area to obtain a core area ground elevation model; the core area ground elevation model and the first elevation model are mosaicked; boundary zone transition fusion is used to smoothly transition the elevation data of the boundary zone between the core area and the outer area in the elevation model obtained after splicing the core area ground elevation model and the first elevation model from the elevation data of the core area ground elevation model to the elevation data of the first elevation model, to obtain the fused target watershed elevation model, so that the core area ground elevation model and the first elevation model are accurately fused, achieving seamless fusion of the core area ground elevation model and the first elevation model, thereby achieving seamless fusion of the oblique photogrammetry model and the first elevation model;

[0055] Secondly, by using the second elevation model of the underwater topography and the fused target watershed elevation model, a water-land area elevation map including the water body area and the water-land transition zone is obtained. The target rendering engine then spatially registers the water-land area topography model generated based on the water-land area elevation map with the preprocessed oblique photogrammetry model, accurately reproducing the positional relationship between the water-land area topography model and the preprocessed oblique photogrammetry model in the real world within a 3D virtual space. Finally, the target rendering engine performs water-land fusion, smoothly transitioning the elevation data of the water-land transition zone between the water body area and the land area in the spatially registered water-land area topography model and the preprocessed oblique photogrammetry model from the elevation data of the water-land area topography model to the elevation data of the preprocessed oblique photogrammetry model, resulting in a fused core area topography model. This allows for precise fusion of the water-land area topography model and the preprocessed oblique photogrammetry model, achieving seamless fusion of the water-land area topography model and the preprocessed oblique photogrammetry model, thereby achieving seamless fusion of the second elevation model and the preprocessed oblique photogrammetry model.

[0056] Thirdly, the elevation data of the target watershed elevation model located in the core area is cropped and fused by the target rendering engine. The elevation data of the fused core area terrain model is used as the elevation data of the core area of ​​the target watershed terrain model, and the elevation data of the fused target watershed elevation model located in the outer area is used as the elevation data of the outer area of ​​the target watershed terrain model. Based on the above-mentioned retained elevation data of the core area and the retained elevation data of the fused target watershed elevation model located in the outer area, the target watershed terrain model is obtained.

[0057] Therefore, the watershed topography model construction method based on multi-source elevation data provided in this application can achieve seamless integration of the target watershed elevation model (i.e., the first elevation model), the underwater topography elevation model (i.e., the second elevation model), and the core area oblique photography model (i.e., the oblique photography model) to construct a seamlessly integrated target watershed topography model, thereby generating a high-quality target watershed topography model.

[0058] The following description Figure 1 Further optional specific embodiments for each step in the watershed terrain model construction process based on multi-source elevation data, as described in the example.

[0059] Step 100: Perform tree removal and water area hollowing preprocessing on the obtained oblique photography model of the core area within the target watershed to obtain the preprocessed oblique photography model.

[0060] In this embodiment, tree removal and water body hollowing are used to remove tree elevation data and water surface elevation data, making the preprocessed oblique photogrammetry model closer to the real terrain.

[0061] In some embodiments, the steps of removing trees and hollowing out water features include: flattening trees in flat areas of the oblique photogrammetry model using an oblique photogrammetry modeling tool, deleting trees in mountainous areas of the oblique photogrammetry model, and patching and texture repairing the hollow areas formed by the deletion process; the step of hollowing out water features includes: deleting triangular facets of the water surface in the water feature area using an oblique photogrammetry modeling tool.

[0062] In some embodiments, the steps of deleting trees in the mountain area of ​​the oblique photogrammetry model and patching and texturing the hollow areas formed by the deletion process include: deleting the triangular facets corresponding to the branches and leaves below the canopy of the trees in the mountain area of ​​the oblique photogrammetry model to obtain the terrain under the trees in the mountain area with hollow areas; patching and texturing the hollow areas to obtain the preprocessed oblique photogrammetry model.

[0063] In some embodiments, the steps of removing trees and hollowing out water features include: importing the oblique photogrammetry model into the oblique photogrammetry modeling tool; flattening the trees in the flat areas of the oblique photogrammetry model to obtain the terrain under the trees in the flat areas; deleting the triangular facets corresponding to the top of the trees to the branches and leaves below the crown of the trees in the mountain areas of the oblique photogrammetry model to obtain the terrain under the trees in the mountain areas with hollow areas; patching and texture repairing the hollow areas; and deleting the triangular facets of the water surface in the water areas.

[0064] In this embodiment, the oblique photography model is imported into the oblique photography model repair tool. The oblique photography model repair tool is used to flatten or delete, patch, and repair the texture of the trees in the oblique photography model to complete the tree removal process. The oblique photography model repair tool is also used to delete the triangular facets of the water surface in the oblique photography model to complete the water body hollowing process.

[0065] For example, importing an oblique photogrammetry model into an oblique photogrammetry modeling tool allows for geometric and texture editing. For example, functional modules within the oblique photogrammetry modeling tool can be used to remove trees and hollow out water features. For instance, a flattening module can be used to flatten the model, a bridging module to form a connecting skeleton, and a hole-filling module to fill voids. For example, the oblique photogrammetry modeling tool can be the oblique photogrammetry modeling software DP-Modeler, or it can be ModelFun.

[0066] In some embodiments, the steps of patching and texture restoration include: completing patching by bridging and filling the void areas to obtain a textureless white film restoration area; and completing texture restoration by performing texture mapping on the textureless white film restoration area to obtain a texture-covered restoration area.

[0067] In some embodiments, the bridging and filling steps include: forming a connecting skeleton between two triangular facets with a relatively large elevation difference at the edge of the cavity area to maintain the continuity of the mountain slope and topography; and performing surface reconstruction on the cavity between the boundary of the cavity area and the boundary of the connecting skeleton to complete the cavity filling and obtain a textureless white film repair area.

[0068] Please see Figure 6 , Figure 6 This illustration shows the process of removing trees from the oblique photogrammetry model of the core area provided in this embodiment to generate a textureless white film restoration area. The oblique photogrammetry model tree removal process generates a textureless white film restoration area.

[0069] In some embodiments, the steps of tree removal and water body hollowing preprocessing include: preparing the oblique photography model (see [reference needed]). Figure 6 a. Import the oblique photogrammetry modeling tool; flatten the trees in flat areas to obtain the understory terrain; for trees in complex mountainous areas, delete the triangular facets corresponding to the branches and leaves below the canopy from the top of the trees to obtain the understory terrain with hollow areas in the mountainous areas. (See also...) Figure 6b; For the hollow areas, surface patching and texture restoration are performed. The surface patching and texture restoration steps include: completing the surface patching by bridging and filling the hollow areas to obtain a textureless white film restoration area; the bridging and filling steps include: forming a connecting skeleton between two triangular facets with relatively large elevation differences at the edge of the hollow area. Please refer to [link to relevant documentation]. Figure 6 c. Used to maintain the slope and topographical continuity of the mountain; surface reconstruction is performed on the boundaries of the cavity area and the cavities connecting the framework boundaries to complete the cavity filling and obtain a textureless white film repair area. Please refer to [link / reference]. Figure 6 d; The texture restoration step includes: performing texture mapping on the textureless white film restoration area to complete the texture restoration, thereby obtaining a restoration area with texture coverage; The water body hollowing step includes: deleting the water surface triangle patches in the water body area to obtain an oblique photography model with tree removal and water body hollowing preprocessing completed.

[0070] Step 200: Obtain the ground elevation model of the core area using the ground point cloud data extracted based on the preprocessed oblique photogrammetry model.

[0071] In this embodiment, ground point cloud is extracted to obtain ground elevation data of the land area within the core area, thus obtaining a ground elevation model of the core area.

[0072] In some embodiments, the step of obtaining a ground elevation model of the core area from ground point cloud data obtained based on a preprocessed oblique photogrammetry model includes:

[0073] For the preprocessed oblique photogrammetry model, the spatial reference information and origin information are analyzed, the position coordinates of the vertices of the triangular facets are extracted, the position coordinates of the extracted triangular facet vertices are corrected, and the initial point cloud data is obtained.

[0074] Ground point cloud data is extracted by filtering the initial point cloud data to remove isolated and noisy point data.

[0075] Based on ground point cloud data, a ground elevation model of the core area is generated using spatial interpolation.

[0076] Understandably, parsing spatial reference information is used to correctly align the position coordinates of the preprocessed oblique photogrammetry model to the spatial reference coordinate system; parsing origin information is used to map and convert the position coordinates of the preprocessed oblique photogrammetry model into real-world position coordinates after parsing spatial reference information. Parsing both spatial reference information and origin information ensures spatial consistency between the extracted ground point cloud data and the preprocessed oblique photogrammetry model. Therefore, for the preprocessed oblique photogrammetry model, parsing spatial reference information and origin information, extracting the position coordinates of the vertices of the triangular facets, and correcting the extracted position coordinates of the triangular facet vertices yields initial point cloud data with real-world geographical location attributes.

[0077] In some embodiments, the steps of parsing spatial reference information and origin information, extracting the position coordinates of the vertices of the triangular facets, correcting the extracted position coordinates of the vertices of the triangular facets, and obtaining the initial point cloud data from the preprocessed oblique photogrammetry model can be completed using the OpenSceneGraph library. In some embodiments, the preprocessed oblique photogrammetry model is in OSGB format. It is understood that the OpenSceneGraph library, abbreviated as OSG, is an open-source 3D graphics rendering engine based on C++. The OpenSceneGraph library can load the preprocessed oblique photogrammetry model in OSGB format using node file reading functions.

[0078] In some embodiments, the step of extracting the position coordinates of the vertices of the triangular facet includes:

[0079] Iterate through all the tile data of the preprocessed oblique photogrammetry model, access all the triangular faces in each tile data, and extract the position coordinates of the vertices of each triangular face.

[0080] It is understandable that the position coordinates of the vertices of the triangle are used to define the position of the vertices of the triangle in the real world, and the spatial reference coordinate system used for the position coordinates is the CGCS2000 coordinate system.

[0081] In some embodiments, the step of correcting the position coordinates of the extracted triangular facet vertices includes:

[0082] The position coordinates of the extracted triangular facet vertices are corrected using the model bounding box of the preprocessed oblique photogrammetry model.

[0083] Understandably, in this embodiment, the origin offset value of the oblique photogrammetry model is used to correct the position coordinates of the extracted triangular facet vertices. The origin offset value of the oblique photogrammetry model comes from the model bounding box of the oblique photogrammetry model. The model bounding box of the oblique photogrammetry model is a minimum cuboid that can just enclose the oblique photogrammetry model, and the origin offset value is provided by the coordinate value of the center point.

[0084] In some embodiments, after extracting the position coordinates of the vertices of the triangular facet, the method further includes:

[0085] Extract the texture coordinates of the vertices of the triangular facet.

[0086] It is understandable that texture coordinates are used to define the sampling positions of the vertices of the triangular facets on a two-dimensional texture image, and the coordinate system used is the texture coordinate system. Therefore, for the preprocessed oblique photogrammetry model, the spatial reference information and origin information are parsed, the position coordinates of the triangular facet vertices are extracted, the extracted position coordinates of the triangular facet vertices are corrected, and the texture coordinates of the triangular facet vertices are extracted to obtain the initial point cloud data, which has real-world geographical location and real-world color attributes.

[0087] In some embodiments, the step of extracting the texture coordinates of the vertices of the triangular facets includes: traversing all tile data of the preprocessed oblique photogrammetry model, accessing all triangular facets in each tile data, and extracting the texture coordinates of the vertices of each triangular facet.

[0088] In some embodiments, after obtaining the initial point cloud data, the method further includes: organizing the obtained initial point cloud data into a unified data structure, constructing a header and scaling factor according to the standard LAS format, and outputting an initial point cloud data file in the standard LAS format, so as to ensure the consistency of the position of the point cloud corresponding to the initial point cloud data with the position of the preprocessed oblique photogrammetry model, and to achieve efficient conversion from the preprocessed oblique photogrammetry model to dense point cloud.

[0089] In some embodiments, after obtaining the initial point cloud data, the method further includes: organizing the obtained initial point cloud data into a unified data structure, constructing a header, scaling factor, and color field according to the standard LAS format, and outputting an initial point cloud data file in the standard LAS format, so as to ensure the consistency of position and color attributes between the point cloud corresponding to the initial point cloud data and the preprocessed oblique photogrammetry model, and to achieve efficient conversion from the preprocessed oblique photogrammetry model to dense point cloud.

[0090] In some embodiments, the step of extracting ground point cloud data after filtering the initial point cloud data to remove isolated point data and noise point data includes:

[0091] The initial point cloud data is first filtered by the local outlier factor algorithm to remove isolated point data and noisy point data, resulting in filtered point cloud data.

[0092] The filtered point cloud data is subjected to a second filtering process using a cloth simulation filtering algorithm to extract ground point cloud data.

[0093] It is understandable that the Local Outlier Factor algorithm can also be called the LOF algorithm; the cloth simulation filtering algorithm can also be called the CSF algorithm. The filtered point cloud data obtained after the first filtering process retains the point cloud data reflecting the overall distribution characteristics of the initial point cloud data. The second filtering process, which uses the cloth simulation filtering algorithm, involves inverting the point cloud corresponding to the filtered point cloud data, placing a layer of virtual cloth on the inverted point cloud surface, and simulating the natural falling process of the virtual cloth. During the fall, the virtual cloth is supported by terrain high points and gradually covers the terrain surface until it stops falling. At this point, the contact surface between the virtual cloth and the point cloud corresponding to the filtered point cloud data is considered the ground. This ground has an approximately coplanar relationship with the ground of the land area in the preprocessed oblique photogrammetry model, especially at the boundaries of the land area. It should be noted that the ground mentioned here does not include trees. Please refer to [link to relevant documentation]. Figure 7 , Figure 7 This is a 3D image obtained by overlaying the core area ground elevation model and the preprocessed oblique photogrammetry model provided in the embodiments of this application. Figure 7 The image clearly shows the ground elevation model of the core area, which is approximately coplanar with the preprocessed oblique photogrammetry model.

[0094] In some embodiments, the step of performing a second filtering process on the filtered point cloud data using a cloth simulation filtering algorithm further includes:

[0095] Adjustments were made to the parameters of fabric stiffness, gravity, and iteration step size to extract ground point cloud data under different terrain conditions.

[0096] Understandably, spatial interpolation is used to transform discrete ground point cloud data into ground elevation models of core areas with continuous surfaces.

[0097] In some embodiments, spatial interpolation can be the inverse distance weighted algorithm, also known as the IDW algorithm; spatial interpolation can also be the natural domain algorithm, the radial basis function (RBF) algorithm, or the Kriging algorithm.

[0098] Step 300: The ground elevation model of the core area and the first elevation model of the target watershed are mosaicked and the boundary zone transition is fused to obtain the fused elevation model of the target watershed.

[0099] In this embodiment, firstly, tree removal and water body hollowing are used to remove tree elevation data and water surface elevation data, making the preprocessed oblique photogrammetry model closer to the real terrain; ground point cloud extraction is used to obtain ground coordinate data and elevation data of the land area within the core area, resulting in a core area ground elevation model; the core area ground elevation model and the first elevation model are mosaicked; boundary zone transition fusion is used to smoothly transition the elevation data of the boundary zone between the core area and the outer area in the elevation model obtained after splicing the core area ground elevation model and the first elevation model from the elevation data of the core area ground elevation model to the elevation data of the first elevation model, resulting in a fused target watershed elevation model, enabling the core area ground elevation model and the first elevation model to be accurately fused, achieving seamless fusion of the core area ground elevation model and the first elevation model, thereby achieving seamless fusion of the oblique photogrammetry model and the first elevation model.

[0100] In some embodiments, the inlay splicing step includes:

[0101] The first elevation model and the ground elevation model of the core area are spatially unified, and the spatial benchmark unification includes spatial reference coordinate system one and elevation benchmark unification.

[0102] For the ground elevation model of the core area after spatial benchmark unification, the pixel boundary between effective elevation value pixels and invalid elevation value pixels is identified, and the first vector polygon boundary of the core area is generated.

[0103] The first elevation model after spatial benchmark unification is resampled to obtain the resampled first elevation model. This resampled first elevation model has the same spatial resolution as the ground elevation model of the core area after spatial benchmark unification.

[0104] Create a first empty target grid of the same size as the first elevation model. Fill the grid within the first vector polygon boundary of the first empty target grid with the core area ground elevation model after spatial benchmark unification. Fill the grid outside the first vector polygon boundary of the first empty target grid with the resampled first elevation model to obtain a preliminary mosaic terrain elevation model.

[0105] Understandably, the first elevation model and the core area ground elevation model are converted to use the same spatial reference coordinate system to eliminate the first position offset caused by the inconsistency of coordinate benchmarks; the first elevation model and the core area ground elevation model are also converted to use the same elevation benchmark to eliminate the elevation system differences caused by the inconsistency of elevation benchmarks.

[0106] For example, the first elevation model uses the WGS84 coordinate system as the spatial reference coordinate system; the oblique photogrammetry model uses the CGCS2000 coordinate system as the spatial reference coordinate system. The first elevation model and the ground elevation model of the core area are combined into the CGCS2000 coordinate system as the spatial reference coordinate system.

[0107] For example, the first elevation model uses the WGS84 geodetic datum; the oblique photogrammetry model uses the 1985 National Elevation Datum. The core area ground elevation model obtained through the oblique photogrammetry model also uses the 1985 National Elevation Datum. The elevation datum is unified between the first elevation model and the core area ground elevation model: the elevation data of the core area ground elevation model remains unchanged, while the elevation data of the first elevation model is converted to use the 1985 National Elevation Datum.

[0108] In some embodiments, an elevation anomaly model can be used to unify the elevation datum between the first elevation model and the core area ground elevation model. For example, this can be achieved using GIS software, specifically geographic information system software. For example, the elevation anomaly model can be the EGM2008 global gravity field model.

[0109] In some embodiments, the boundary band transition fusion step includes:

[0110] Based on the preliminary mosaic terrain elevation model, a boundary zone is formed inward from the boundary of the first vector polygon.

[0111] Calculate the distance between each pixel within the boundary band and the boundary of the first vector polygon to obtain the first distance;

[0112] The fused elevation value is obtained by weighting and averaging the first elevation value of each pixel within the boundary zone, which originates from the first elevation model after resampling, and the second elevation value, which originates from the ground elevation model of the core area after spatial benchmark unification. The weight of the first elevation value is negatively correlated with the first distance, and the weight of the second elevation value is positively correlated with the first distance.

[0113] The fused elevation values ​​are filled into the corresponding pixels to obtain a fused target watershed elevation model with a smooth transition and seamless connection at the boundary of the first vector polygon.

[0114] Understandably, a preliminary mosaic terrain elevation model is obtained by mosaicking the ground elevation model of the core area with the first elevation model. Please refer to [link / reference needed]. Figure 8Because the ground elevation model of the core area and the first elevation model have different data sources and accuracies, even after processing to ensure spatial reference coordinate system consistency and spatial resolution uniformity, elevation deviations still exist. This results in abrupt elevation changes at the first vector polygon boundary of the preliminary mosaic terrain elevation model obtained after stitching. Figure 8 The elevation change shown in the red box is the aforementioned abrupt change.

[0115] Understandably, the core area ground elevation model and the first elevation model are mosaicked and merged, and the boundary zone transition is integrated to obtain the merged target watershed elevation model. Please refer to [link / reference needed]. Figure 9 After boundary zone transition fusion, the elevation abrupt changes in the first vector polygon boundary of the initial mosaic terrain elevation model were eliminated, resulting in a fused target watershed elevation model with a smooth and seamless elevation transition at the first vector polygon boundary. Figure 9 As shown in the red box, the elevation transitions smoothly and seamlessly at the boundary of the first vector polygon.

[0116] In some embodiments, the step of identifying the pixel boundaries between valid and invalid elevation value pixels and generating the first vector polygon boundary of the core area in the ground elevation model of the core area after spatial benchmark unification includes:

[0117] Using a grid data processing algorithm, the pixel boundary between effective and invalid elevation value pixels in the ground elevation model of the core area after spatial benchmark unification is identified.

[0118] Based on the identified pixel boundaries, the first vector polygon boundary of the core region is generated using a grid-to-vector conversion algorithm.

[0119] For example, the grid data processing algorithm can be provided through the grid toolset in GIS software; the grid-to-vector conversion algorithm can be provided through the grid-to-vector conversion tool in GIS software. It is understood that the grid-to-vector conversion algorithm includes a contour tracking algorithm. The step of generating the first vector polygon boundary can also be: generating the first vector polygon boundary of the core area using the globalmapper software on the ground elevation model of the core area after spatial benchmark unification. Alternatively, the step of generating the first vector polygon boundary can be: generating the first vector polygon boundary of the core area using the rasterio features shapes function on the ground elevation model of the core area after spatial benchmark unification.

[0120] Understandably, a pixel is the smallest unit of grid data that constitutes an elevation model, and it is also a grid unit that includes spatial location information and elevation value information.

[0121] It is understandable that a valid elevation value pixel refers to a pixel with elevation data, and the collective valid elevation value pixels constitute the valid elevation data area; an invalid elevation value pixel refers to a pixel that does not have elevation data and only has an elevation data missing identifier, and the collective invalid elevation value pixels constitute the invalid elevation data area; the pixel boundary is the pixel boundary of the valid elevation data area, the pixel boundary of the invalid elevation data area, and also the pixel boundary of the core area. The first vector polygon boundary is used to define the contact range between the core area and the outer area, and serves as a boundary reference for subsequent mosaicking and boundary zone transition fusion of the core area ground elevation model and the first elevation model.

[0122] In some embodiments, the resampling step includes: obtaining a resampled first elevation model using a resampling tool in GIS software. Specifically, this can be achieved by using the cubic convolution interpolation method in the resampling tool of the GIS software to obtain the resampled first elevation model. It is understood that the resampled first elevation model having the same spatial resolution as the core area ground elevation model means that the pixel size of the resampled first elevation model is consistent with that of the core area ground elevation model. For example, if the spatial resolution of the elevation model is 0.5 meters, that is, the pixel size is 0.5 meters × 0.5 meters, it means that each pixel of the elevation model corresponds to a 0.5 meter × 0.5 meter grid area in the real world.

[0123] It is understood that the resampling is used to fully align the pixels of the first elevation model with the pixels of the core area ground elevation model, thereby achieving pixel-level georegistration.

[0124] Understandably, based on the boundary of the first vector polygon, the ground elevation model of the core area after the spatial benchmark is unified is stitched together with the first elevation model after resampling. Since the two models have different data sources and different data precision, although the spatial reference coordinate system and the pixels are fully aligned, there will still be elevation deviations. This results in the preliminary mosaic terrain elevation model obtained after stitching having elevation abrupt changes at the boundary of the first vector polygon.

[0125] It is understood that the boundary zone in the step of forming a boundary zone inward based on the boundary of the first vector polygon as a reference, based on the preliminary mosaic terrain elevation model, is a ring-shaped area with a certain width, serving as a transition area between the resampled first elevation model and the core area ground elevation model after spatial benchmark unification.

[0126] The first elevation value is the elevation value of each pixel within the boundary band, derived from the resampled first elevation model. The second elevation value is the elevation value of each pixel within the boundary band, derived from the core area ground elevation model after spatial benchmark unification. A weighted average of the first and second elevation values ​​for each pixel in the boundary band is used to obtain the fused elevation value for each pixel. The weight of the first elevation value is negatively correlated with the first distance, while the weight of the second elevation value is positively correlated with the first distance. This ensures that pixels closer to the boundary of the first vector polygon retain more of the first elevation value, and pixels farther from the boundary retain more of the second elevation value. Based on the optimized elevation values ​​of each pixel, a boundary band with smooth elevation transition and seamless connection is obtained, leading to a fused target watershed elevation model with smooth elevation transition and seamless connection at the boundary of the first vector polygon.

[0127] For example, the "Mottling to New Raster" tool in GIS software can be used to fill the first empty target raster with the ground elevation model of the core area after spatial benchmark unification. The step of forming a boundary zone inward based on the initial mosaic terrain elevation model and using the boundary of the first vector polygon as a reference can be completed within the GIS software.

[0128] In some embodiments, the step of forming a boundary band inward based on the boundary of the first vector polygon and using the preliminary mosaic terrain elevation model as a reference further includes: forming the boundary band with the same width.

[0129] In the step of weighted averaging the first elevation value of each pixel within the boundary zone, derived from the first elevation model after resampling, and the second elevation value, derived from the ground elevation model of the core area after spatial benchmark unification, the formula for weighted averaging is:

[0130] ,

[0131] ,

[0132] in, The merged elevation value of pixel (x,y);

[0133] Let (x,y) be the first elevation value corresponding to the pixel (x,y) derived from the first elevation model after resampling;

[0134] The second elevation value corresponding to pixel (x,y) is derived from the ground elevation model of the core area after the spatial benchmark unification.

[0135] for The corresponding weight of the first elevation value;

[0136] for The corresponding weight of the second elevation value;

[0137] For pixels The distance to the boundary of the first vector polygon is the first distance;

[0138] This is the boundary band transition smoothing factor, which is equal to the width of the boundary band.

[0139] It is understood that in this embodiment, the boundary band is a constant width boundary band, and the boundary band transition smoothing factor is... It equals the width of the boundary band.

[0140] When pixel When located at the boundary of the first vector polygon in the boundary zone, =0, =1, =0, at this time The weight of the corresponding first elevation value is 1. The weight of the corresponding second elevation value is 0. The first elevation value was used, which is The first elevation model after resampling was used. The elevation value.

[0141] When pixel When located on another boundary in the boundary zone opposite to the boundary of the first vector polygon. = , =0, =1, at this time The weight of the corresponding first elevation value is 0. The weight of the corresponding second elevation value is 1. The second elevation value was used, which is The core area ground elevation model adopted after the spatial benchmark unification is in (Elevation value.)

[0142] Step 400: Based on the second elevation model of the underwater topography of the water body area within the core area and the fused target watershed elevation model, a water-land area elevation map including the water body area and the water-land transition zone is obtained; the water-land area topography model generated based on the water-land area elevation map and the preprocessed oblique photogrammetry model are spatially registered and fused using a target rendering engine to obtain the fused core area topography model.

[0143] In this embodiment, a water-land area elevation map, including the water body area and the water-land transition zone, is obtained by using the second elevation model of the underwater topography and the fused target watershed elevation model. A target rendering engine is used to spatially register the water-land area topography model generated based on the water-land area elevation map and the preprocessed oblique photogrammetry model. This is used to accurately recreate the positional relationship between the water-land area topography model and the preprocessed oblique photogrammetry model in the real world within a 3D virtual space. The target rendering engine then performs water-land fusion, smoothly transitioning the elevation data of the water-land transition zone between the water body area and the land area in the spatially registered water-land area topography model and the preprocessed oblique photogrammetry model from the elevation data of the water-land area topography model to the elevation data of the preprocessed oblique photogrammetry model. This results in a fused core area topography model, enabling precise fusion of the water-land area topography model and the preprocessed oblique photogrammetry model, achieving seamless fusion of the water-land area topography model and the preprocessed oblique photogrammetry model, thereby achieving seamless fusion of the second elevation model and the preprocessed oblique photogrammetry model.

[0144] In some embodiments, the step of obtaining a water-land area elevation map including the water body area and the water-land transition zone based on the second elevation model of the underwater topography of the water body area within the core area and the fused target watershed elevation model includes:

[0145] The first address of the preprocessed oblique photogrammetry model is loaded into the target rendering engine; the second address of the fused target watershed elevation model is loaded into the target rendering engine.

[0146] After unifying the spatial reference of the second elevation model and the fused target watershed elevation model, the second elevation model is embedded into the water area of ​​the fused target watershed elevation model to obtain a water-land mosaic topographic model.

[0147] Based on the new boundary formed by expanding the hollow boundary of the water area of ​​the preprocessed oblique photography model by a certain distance, the water-land mosaic terrain model is trimmed to obtain a water-land area elevation model including the water area and the water-land transition zone.

[0148] The elevation model of the land and water area is used to generate an elevation map of the land and water area using an elevation map generation tool.

[0149] As can be understood, a land-water area height map is a grayscale image that uses pixel grayscale values ​​to encode the elevation information of a land-water area. The land-water area includes the water body and the transition zone between land and water. For example, a height map generation tool could be CesiumLab software.

[0150] In some embodiments, the step of unifying spatial references includes:

[0151] For the second elevation model and the fused target watershed elevation model, the spatial reference coordinate system and elevation datum are unified.

[0152] In some embodiments, the step of embedding the second elevation model into the water body region of the fused target watershed elevation model includes:

[0153] For the second elevation model after spatial benchmark unification, the pixel boundary between effective elevation value pixels and invalid elevation value pixels is identified to generate the second vector polygon boundary of the water body area;

[0154] The target watershed elevation model after spatial benchmark unification and fusion is resampled to obtain the resampled fusion target watershed elevation model. This resampled fusion target watershed elevation model has the same spatial resolution as the second elevation model after spatial benchmark unification.

[0155] Create a second empty target grid of the same size as the merged target watershed elevation model. Fill the grid within the second vector polygon boundary of the second empty target grid with the second elevation model after spatial benchmark unification. Fill the grid outside the second vector polygon boundary of the second empty target grid with the resampled merged target watershed elevation model to obtain a land-water mosaic terrain model.

[0156] The steps of generating a height map of the land and water area from the elevation model of the land and water area using a height map generation tool include:

[0157] CesiumLab software was used as the heightmap generation tool;

[0158] The origin of the land and water area elevation model is set using CesiumLab software. This origin is then aligned with the Cesium geographic origin in the target rendering engine. The land and water area elevation model is then used to generate a land and water area height map. During the generation of the height map, the spatial resolution, segment size, and number of components are set. The spatial resolution of the land and water area height map is set based on the grid size of the second elevation model.

[0159] Understandably, please refer to Figure 10 , Figure 10 The image shows an elevation model obtained by mosaicking the second elevation model and the fused target watershed elevation model, replacing the water area portion of the fused target watershed elevation model with the second elevation model. The fused target watershed elevation model is based on an oblique photogrammetry model. Due to the different data sources and accuracies of the second elevation model and the oblique photogrammetry model, there is an elevation deviation at the mosaicking interface, resulting in an unnatural stepped protrusion at the land-water junction after mosaicking. Figure 10 As shown in the red box.

[0160] It is understandable that the spatial resolution is equal to the pixel size, which is also equal to the grid size. The number of components (or data blocks) refers to the total number of components (or data blocks) formed after the elevation model data is divided. The segment size refers to the total number of grids contained in a component (or data block).

[0161] In some embodiments, the step of spatially registering and fusing the land and water area terrain model with the preprocessed oblique photogrammetry model using a target rendering engine to obtain a fused core area terrain model includes:

[0162] Import the elevation map of the land and water area into the target rendering engine; use the target rendering engine to generate a terrain model of the land and water area from the elevation map of the land and water area.

[0163] Spatial registration is performed between the land and water terrain model and the preprocessed oblique photogrammetry model to form the land-water transition area. The land-water transition area is then geometrically repaired using the brush tool in the target rendering engine to obtain a seamlessly integrated core area terrain model.

[0164] Understandably, the brush tool is used to perform geometric repair on the water-land interface. This geometric repair method restores the physical structure of the water-land interface, achieving a seamless physical integration. Please refer to [link / reference needed]. Figure 11 a.

[0165] In some embodiments, the step of generating a land and water area elevation map into a land and water area terrain model using a target rendering engine further includes:

[0166] During the generation of the land and water area terrain model, the spatial resolution, segment size, and number of components of the land and water area terrain model are set according to the spatial resolution, segment size, and number of components of the land and water area elevation map to ensure that the terrain size of the generated land and water area terrain model is consistent with the terrain size of the land and water area elevation model.

[0167] In some embodiments, geometric repair includes: smoothing, sculpting, and leveling. In some embodiments, the step of geometrically repairing the land-water junction area using brush tools in the target rendering engine includes: smoothing and softening the stepped protrusions formed in the land-water junction area using a smoothing brush tool. In some embodiments, the step of geometrically repairing the land-water junction area further includes: aligning and interlocking the gaps and elevation misalignments formed in the land-water junction area using a sculpting brush tool. In some embodiments, the step of geometrically repairing the land-water junction area further includes: setting a target height and uniformly adjusting the riverbank line in the land-water junction area that needs to maintain a specific shape using a leveling brush tool.

[0168] Understandably, after spatial registration of the land and water terrain model and the preprocessed oblique photogrammetry model, the target rendering engine can accurately reproduce their spatial relationship in the real world.

[0169] In some embodiments, after the step of geometrically repairing the water-land interface area using a brush tool in the target rendering engine, the method further includes:

[0170] Materials are created in the target rendering engine and then applied to the terrain model of the land and water areas.

[0171] Understandably, the created materials are applied to the terrain model of the land and water areas. By applying materials, the areas where land and water meet are refined, achieving not only a seamless physical integration but also a seamless visual integration. Please refer to [link / reference needed]. Figure 11 b.

[0172] For example, the steps of creating a material in the target rendering engine and assigning the created material to the water and land terrain model may include: creating a PBR material in the target rendering engine's browser, loading color maps, normal maps, and roughness maps of underwater mud, pebbles, etc., that meet the target resolution from the 3D material resource library integrated into the target rendering engine, configuring the material network, and creating a material instance; and assigning the created material instance to the water and land terrain model in the target rendering engine.

[0173] Step 500: Using the target rendering engine, trim the elevation data of the core area of ​​the merged core region terrain model and the merged target watershed elevation model to obtain the target watershed terrain model. (See also...) Figure 11 b and Figure 12 .

[0174] In this embodiment, the elevation data of the target watershed elevation model located in the core area is cropped and fused by the target rendering engine. The elevation data of the fused core area terrain model is used as the elevation data of the core area of ​​the target watershed terrain model, and the elevation data of the fused target watershed elevation model located in the outer area is used as the elevation data of the outer area of ​​the target watershed terrain model. Based on the above-mentioned retained elevation data of the core area and the retained elevation data of the fused target watershed elevation model located in the outer area, the target watershed terrain model is obtained.

[0175] Therefore, the watershed topography model construction method based on multi-source elevation data provided in this application can achieve seamless integration of the target watershed elevation model (i.e., the first elevation model), the underwater topography elevation model (i.e., the second elevation model), and the core area oblique photography model (i.e., the oblique photography model) to construct a seamlessly integrated target watershed topography model, thereby generating a high-quality target watershed topography model.

[0176] Figure 13 This is a schematic diagram of the watershed terrain model construction system based on multi-source elevation data provided in this embodiment of the application. Please refer to... Figure 13 The watershed terrain model construction system based on multi-source elevation data may include a preprocessing module 510, an extraction module 520, a first fusion module 530, a second fusion module 540, and a trimming module 550. Wherein:

[0177] Preprocessing module 510 is used to perform tree removal and water area hollowing preprocessing on the acquired oblique photography model of the core area within the target watershed to obtain the preprocessed oblique photography model.

[0178] The extraction module 520 is used to obtain the ground elevation model of the core area from the ground point cloud data extracted based on the preprocessed oblique photogrammetry model.

[0179] The first fusion module 530 is used to perform mosaic stitching and boundary zone transition fusion on the ground elevation model of the core area and the first elevation model of the target watershed, so as to obtain the fused elevation model of the target watershed.

[0180] The second fusion module 540 is used to obtain a water-land area elevation map including the water body area and the water-land transition zone based on the second elevation model of the underwater topography of the water body area within the core area and the fused target watershed elevation model; and to perform spatial registration and water-land connection fusion of the water-land area topography model generated based on the water-land area elevation map and the preprocessed oblique photography model through the target rendering engine to obtain the fused core area topography model.

[0181] The clipping module 550 is used to clip the elevation data of the core area of ​​the fused core area terrain model and the fused target watershed elevation model through the target rendering engine to obtain the target watershed terrain model.

[0182] In practical applications, the aforementioned system can be a terminal device or a chip applied to a terminal device. In this application, the system can implement the functions of multiple units through software, hardware, or a combination of both, enabling the system to execute the watershed terrain model construction method steps based on multi-source elevation data provided in any of the above embodiments. Furthermore, the technical effects of each technical solution in this system can be referenced to the corresponding technical effects in the watershed terrain model construction method based on multi-source elevation data; these will not be elaborated upon further in this application.

[0183] Figure 14 This is a schematic diagram of the structure of the electronic device provided in the embodiments of this application.

[0184] Based on the hardware implementation of each unit in the above system, embodiments of this application also provide an electronic device, such as... Figure 14 As shown, the electronic device 80 includes a memory 810 and a processor 820. The memory 810 stores a computer program, and the processor 820 executes the computer program to implement the steps of the watershed terrain model construction method based on multi-source elevation data provided in any of the above embodiments.

[0185] Of course, in practical applications, such as Figure 14 As shown, the various components in the electronic device 80 are coupled together via a bus system 830. It can be understood that the bus system 830 is used to enable communication between these components. In addition to a data bus, the bus system 830 also includes a power bus, a control bus, and a status signal bus. However, for clarity, all buses are labeled as bus system 830 in the figure.

[0186] In practical applications, the aforementioned processor can be at least one of the following: Application-Specific Integrated Circuit (ASIC), Digital Signal Processing Device (DSPD), Programmable Logic Device (PLD), Field-Programmable Gate Array (FPGA), controller, microcontroller, and microprocessor. It is understood that, for different devices, the electronic devices used to implement the functions of the aforementioned processor can also be other types, and the embodiments of this application do not specifically limit this.

[0187] The aforementioned memory can be volatile memory, such as random-access memory (RAM); or non-volatile memory, such as read-only memory (ROM), flash memory, hard disk drive (HDD), or solid-state drive (SSD); or a combination of the above types of memory, and provides instructions and data to the processor.

[0188] The electronic devices described in the embodiments of this application can be terminal devices or chips applied to terminal devices. The terminal devices described in the embodiments of this application can include computers and other terminal devices.

[0189] In an exemplary embodiment, this application also provides a computer-readable storage medium, such as a memory including a computer program, which can be executed by a processor of an electronic device to perform the steps of the aforementioned method.

[0190] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the steps of the method described in any one of the embodiments of this application.

[0191] Optionally, the computer program product can be applied to the electronic device in the embodiments of this application, and the computer program instructions cause the computer to execute the corresponding processes implemented by the electronic device in the various methods of the embodiments of this application. For the sake of brevity, they will not be described in detail here.

[0192] This application also provides a computer program.

[0193] Optionally, the computer program can be applied to the electronic device in the embodiments of this application. When the computer program is run on a computer, it causes the computer to execute the corresponding processes implemented by the electronic device in the various methods of the embodiments of this application. For the sake of brevity, it will not be described in detail here.

[0194] It should be understood that in the embodiments of this application, data such as user information are involved. When the embodiments of this application are applied to specific products or technologies, user permission or consent is required, and the collection, use and processing of related data must comply with the relevant laws, regulations and standards of the relevant countries and regions.

[0195] It should be understood that the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items. The expressions “having,” “may have,” “comprising,” and “including,” or “may include” and “may contain” used herein may be used to indicate the presence of a corresponding feature (e.g., an element such as a number, function, operation, or component), but do not exclude the presence of additional features.

[0196] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another, and are not necessarily used to describe a specific order or sequence. For example, without departing from the scope of this invention, first information may also be referred to as second information, and similarly, second information may also be referred to as first information.

[0197] The technical solutions described in the embodiments of this application can be combined arbitrarily without conflict.

[0198] In the embodiments provided in this application, it should be understood that the disclosed methods, systems, and devices can be implemented in other ways. The embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or units can be electrical, mechanical, or other forms.

[0199] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the units may be selected to achieve the purpose of this embodiment according to actual needs.

[0200] In addition, each functional unit in the various embodiments of this application can be integrated into one processing unit, or each unit can be a separate unit, or two or more units can be integrated into one unit; the integrated unit can be implemented in hardware or in the form of hardware plus software functional units.

[0201] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for constructing a watershed topographic model based on multi-source elevation data, characterized in that, include: The oblique photography model of the core area within the target watershed is preprocessed by removing trees and hollowing out water areas to obtain the preprocessed oblique photography model. A ground elevation model of the core area is obtained by extracting ground point cloud data based on the preprocessed oblique photogrammetry model. The ground elevation model of the core area and the first elevation model of the target watershed are mosaicked and the boundary zone transition is fused to obtain the fused elevation model of the target watershed. Based on the second elevation model of the underwater topography of the water body area within the core area and the fused target watershed elevation model, a water-land area elevation map including the water body area and the water-land transition zone is obtained. The water-land area topography model generated based on the water-land area elevation map and the preprocessed oblique photogrammetry model are spatially registered and fused with the water-land connection through the target rendering engine to obtain the fused core area topography model. The target watershed terrain model is obtained by cropping the elevation data of the core area of ​​the fused core area terrain model and the fused target watershed elevation model through the target rendering engine. The mosaicking process includes: unifying the spatial reference of the first elevation model and the ground elevation model of the core area, wherein the spatial reference unification includes a spatial reference coordinate system and elevation reference unification; identifying the pixel boundaries between valid and invalid elevation value pixels in the ground elevation model of the core area after spatial reference unification, and generating the first vector polygon boundary of the core area; resampling the first elevation model after spatial reference unification to obtain a resampled first elevation model, which has the same spatial resolution as the ground elevation model of the core area after spatial reference unification; creating a first empty target grid of the same size as the first elevation model; filling the grid within the first vector polygon boundary of the first empty target grid with the ground elevation model of the core area after spatial reference unification; and filling the grid outside the first vector polygon boundary of the first empty target grid with the resampled first elevation model to obtain a preliminary mosaic terrain elevation model. The generation steps of the water and land area elevation map specifically include: loading the first address of the preprocessed oblique photogrammetry model to the target rendering engine; loading the second address of the fused target watershed elevation model to the target rendering engine; after unifying the spatial reference of the second elevation model and the fused target watershed elevation model, embedding the second elevation model into the water body area of ​​the fused target watershed elevation model to obtain a water and land mosaic terrain model; based on the new boundary formed by expanding the hollow boundary of the water body area of ​​the preprocessed oblique photogrammetry model, trimming the water and land mosaic terrain model to obtain a water and land area elevation model including the water body area and the water and land transition zone; and generating a water and land area elevation map using a elevation map generation tool.

2. The method for constructing a watershed topographic model based on multi-source elevation data according to claim 1, characterized in that, The step of obtaining the ground elevation model of the core area from the ground point cloud data extracted based on the preprocessed oblique photogrammetry model includes: For the preprocessed oblique photogrammetry model, the spatial reference information and origin information are analyzed, the position coordinates of the vertices of the triangular facets are extracted, the position coordinates of the extracted triangular facet vertices are corrected, and the initial point cloud data is obtained. Ground point cloud data is extracted by filtering the initial point cloud data to remove isolated and noisy point data. Based on ground point cloud data, a ground elevation model of the core area is generated using spatial interpolation.

3. The method for constructing a watershed topographic model based on multi-source elevation data according to claim 1, characterized in that, The boundary band transition fusion step includes: Based on the preliminary mosaic terrain elevation model, a boundary zone is formed inward from the boundary of the first vector polygon. Calculate the distance between each pixel within the boundary band and the boundary of the first vector polygon to obtain the first distance; The fused elevation value is obtained by weighting and averaging the first elevation value of each pixel within the boundary zone, which originates from the first elevation model after resampling, and the second elevation value, which originates from the ground elevation model of the core area after spatial benchmark unification. Among them, the weight of the first elevation value is negatively correlated with the first distance, and the weight of the second elevation value is positively correlated with the first distance. The fused elevation values ​​are filled into the corresponding pixels to obtain a fused target watershed elevation model with a smooth transition and seamless connection at the boundary of the first vector polygon.

4. The method for constructing a watershed topographic model based on multi-source elevation data according to claim 3, characterized in that, The step of forming a boundary band inward based on the boundary of the first vector polygon as a reference, based on the preliminary mosaic terrain elevation model, further includes: forming the boundary band with the same width. In the step of weighted averaging the first elevation value of each pixel within the boundary zone, derived from the first elevation model after resampling, and the second elevation value, derived from the ground elevation model of the core area after spatial benchmark unification, the formula for weighted averaging is: ， ， in, The merged elevation value of pixel (x,y); Let (x,y) be the first elevation value corresponding to the pixel (x,y) derived from the first elevation model after resampling; The second elevation value corresponding to pixel (x,y) is derived from the ground elevation model of the core area after the spatial benchmark unification. for The corresponding weight of the first elevation value; for The corresponding weight of the second elevation value; For pixels The distance to the boundary of the first vector polygon is the first distance; This is the boundary band transition smoothing factor, which is equal to the width of the boundary band.

5. The method for constructing a watershed topographic model based on multi-source elevation data according to claim 1, characterized in that, The steps of spatially registering and fusing the terrain model of the land and water region generated based on the elevation map of the land and water region with the preprocessed oblique photogrammetry model through a target rendering engine to obtain the fused core region terrain model include: Import the elevation map of the land and water area into the target rendering engine; use the target rendering engine to generate a terrain model of the land and water area from the elevation map of the land and water area. Spatial registration is performed between the land and water terrain model and the preprocessed oblique photogrammetry model to form a land-water transition area. The land-water transition area is then geometrically repaired using the brush tool in the target rendering engine to obtain a seamlessly integrated core area terrain model.

6. A watershed topographic model construction system based on multi-source elevation data, characterized in that, include: The preprocessing module is used to perform tree removal and water area hollowing preprocessing on the oblique photography model of the core area within the target watershed, so as to obtain the preprocessed oblique photography model. The extraction module is used to obtain the ground elevation model of the core area from the ground point cloud data extracted based on the preprocessed oblique photogrammetry model. The first fusion module is used to perform mosaic stitching and boundary zone transition fusion on the ground elevation model of the core area and the first elevation model of the target watershed, so as to obtain the fused elevation model of the target watershed. The second fusion module is used to obtain a water-land area elevation map including the water body area and the water-land transition zone based on the second elevation model of the underwater topography of the water body area in the core area and the fused target watershed elevation model; the water-land area topography model generated based on the water-land area elevation map and the preprocessed oblique photogrammetry model are spatially registered and water-land connection fused by the target rendering engine to obtain the fused core area topography model. The trimming module is used to trim the elevation data of the core area of ​​the fused core area terrain model and the fused target watershed elevation model through the target rendering engine to obtain the target watershed terrain model. The first fusion module is further configured to: unify the spatial reference of the first elevation model and the ground elevation model of the core area, wherein the spatial reference unification includes a spatial reference coordinate system and elevation reference unification; identify the pixel boundaries between valid elevation value pixels and invalid elevation value pixels in the ground elevation model of the core area after spatial reference unification, and generate the first vector polygon boundary of the core area; resample the first elevation model after spatial reference unification to obtain a resampled first elevation model, wherein the resampled first elevation model has the same spatial resolution as the ground elevation model of the core area after spatial reference unification; create a first empty target grid of the same size as the first elevation model; fill the grid within the first vector polygon boundary of the first empty target grid with the ground elevation model of the core area after spatial reference unification; and fill the grid outside the first vector polygon boundary of the first empty target grid with the resampled first elevation model to obtain a preliminary mosaic terrain elevation model; The second fusion module is further configured to: load the first address of the preprocessed oblique photogrammetry model to the target rendering engine; load the second address of the fused target watershed elevation model to the target rendering engine; after unifying the spatial reference of the second elevation model and the fused target watershed elevation model, embed the second elevation model into the water body area of ​​the fused target watershed elevation model to obtain a water-land mosaic terrain model; based on the new boundary formed by expanding the hollow boundary of the water body area of ​​the preprocessed oblique photogrammetry model, trim the water-land mosaic terrain model to obtain a water-land area elevation model including the water body area and the water-land transition zone; and generate a water-land area elevation map using a height map generation tool.

7. An electronic device, characterized in that, It includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the steps of the watershed terrain model construction method based on multi-source elevation data provided in any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the watershed terrain model construction method based on multi-source elevation data provided in any one of claims 1 to 5.

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