Multi-resolution river network spatial data fusion assimilation method

Abstract

The invention provides a multi-resolution river network spatial data fusion assimilation method. The method comprises the following steps: extracting river reach from a hydrodriver data set and integrating the river reach into a complete river; an OSM river center line associated with each hydrodriver river is selected from the OSM river center line map layer; the OSM river center line coordinates are fused into a hydrodriver river, and the OSM river center line coordinates are fused into the hydrodriver river; the topological relation of each hydrodriver river is restored; and screening and manually repairing the abnormal river reach. According to the multi-resolution river network spatial data fusion assimilation method provided by the invention, the river similarity is judged through multiple constraints such as the spatial distance and the topological relation, and then fusion of rivers with different resolutions is realized by adopting multiple distances.

Description

Technical Field

[0001] The invention relates to the technical field of remote sensing target recognition, in particular to a multi-resolution river network spatial data fusion and assimilation method. Background Art

[0002] With the continuous advancement of large-scale data acquisition technologies such as satellite remote sensing and drones, data production methods have gradually diversified, resulting in a variety of data resources from different sources and resolutions. This increasing abundance of data resources has also led to conflicts between similar data from different sources, causing significant inconvenience for data users. Currently, there are two main methods for producing river data. The first method uses GIS software based on high-resolution terrain data to generate topological river centerlines and topological networks based on hydrological confluence relationships. The second method utilizes high-resolution remote sensing imagery to obtain river centerline or surface data through image classification or manual mapping. River data obtained using these two methods each have advantages and disadvantages. River data extracted using terrain data has good topological relationships and offers significant advantages in hydrological calculations. However, due to the influence of terrain accuracy, the spatial accuracy of river centerlines is low, especially in flat areas, where river lines deviate significantly from the actual river direction. River data obtained using high-resolution remote sensing imagery has high spatial resolution, but because many rivers are seasonal, it is difficult to obtain a complete picture of the river from remote sensing imagery alone, especially during the dry season, when rivers extracted from remote sensing imagery are difficult to obtain continuously. Furthermore, the topological relationships of rivers cannot be obtained from remote sensing imagery, so remote sensing imagery can only be used for display purposes and cannot meet the needs of professional applications such as hydrological simulation and analysis. Currently, the two most popular and widely used types of river data are hydroriver and river data from the OpenStreetMap dataset (OSM), both of which have global coverage. HydroRiver mainly uses terrain data extraction and has very accurate and complete topological relationships, including river direction, catchment area, length and other information; the OSM river layer is drawn by many users based on remote sensing images or high-precision maps, with high spatial resolution, but there is a lack of topological relationships between rivers, many rivers are missing, and the data is not standardized enough.

[0003] Patent application number CN107423753A discloses a rapid fusion calculation method for multi-source spatial data, comprising the following steps: data format conversion, data gridding, data normalization, and data fusion. Data in different formats are converted into NetCDF raster data files. Using R programming, a unified spatial resolution and grid coordinates are applied to different raster data layers, and the raster data layers are standardized to obtain a normalized data source with the same spatial geographic location. Data layers from different sources and formats are unified in resolution and spatial geographic grid. Using R programming, vector polygons of the study area are used to cut the different data layers, resulting in polygonal NetCDF format data layers. Weight coefficients are assigned to each data layer based on the research objectives, and a mathematical model is established. Numerical calculations based on the model are then performed to determine the spatial distribution of the objective function. However, this method is based on the traditional concept of extracting vectors from raster data and employs raster-vector overlay analysis, making it incapable of multi-resolution vector data fusion.

[0004] In November 2021, the 11th issue of "Guangdong Water Conservancy and Hydropower" magazine published an article titled "Research and Application of River Data Fusion Technology Taking Spatial Relationships into Account" by Shan Senhua, Wang Zhanyou, Feng Min, Lin Ping, and Lin Ming. Based on river coding and digital elevation models, the article establishes a one-to-many or many-to-one association mapping between river sections and between rivers and river-related projects, and automatically aggregates their spatial, attribute, video and other data. A river data fusion technology that takes spatial relationships into account is proposed to systematically reflect the spatial relationship between rivers and river-related objects. It is hoped that this will provide a reference for reducing the cost of river spatial data association processing and enhancing the application value of river spatial data. The disadvantage of this method is that it processes a single type of river data, uses spatial relationships to realize river data integration and establish relationships between water conservancy projects, and cannot fuse multiple types of river data with different resolutions. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes a multi-resolution river network spatial data fusion and assimilation method, which judges the similarity of rivers through multiple constraints such as spatial distance and topological relationship, and then uses multiple distances to achieve the fusion of rivers with different resolutions.

[0006] The present invention aims to provide a multi-resolution river network spatial data fusion and assimilation method, which includes extracting river sections from a hydroriver dataset and integrating them into complete rivers, and further includes the following steps:

[0007] Step 1: Select the OSM river centerline associated with each hydroriver from the OSM river centerline layer;

[0008] Step 2: Merge the OSM river centerline coordinates into the hydroriver river;

[0009] Step 3: Repair the topological relationship of each hydroriver;

[0010] Step 4: Screen and manually repair abnormal river sections.

[0011] Preferably, extracting river sections from the hydroriver dataset and integrating them into a complete river comprises the following sub-steps:

[0012] Step 01: Save the river segments from HydroRiver in a separate layer. The river is divided into many segments in this layer.

[0013] Step 02: Integrate the river sections into complete rivers based on their confluence relationships.

[0014] In any of the above schemes, it is preferred that the river section integration method includes tracing back upstream from the terminal river section to the upstream source river section, accumulating the total length of each source river section to the terminal river section, and integrating all river sections from the source river section with the largest total length to the terminal river section into a complete river.

[0015] In any of the above solutions, preferably, step 02 includes the following sub-steps:

[0016] Step 021: All river sections flowing into the river are taken as new terminal river sections and integrated according to the river section integration method to obtain all first-level rivers;

[0017] Step 022: All river sections flowing into the first-level river are taken as new terminal river sections and integrated according to the river section integration method to obtain all second-level rivers;

[0018] Step 023: The river sections flowing into the secondary rivers are regarded as the terminal rivers, and are integrated according to the river section integration method to obtain all the third-level rivers;

[0019] Step 024: Integrate all river sections into a complete river according to the river section integration method;

[0020] Step 025: After all rivers are integrated, the code of the source river section is used as the code of the river.

[0021] In any of the above solutions, preferably, step 1 includes the following sub-steps:

[0022] Step 11: Create a 5km buffer using each complete hydroriver, and select the OSM river centerline that intersects the buffer as the candidate river centerline for the river.

[0023] Step 12: Calculate the average distance, number of closest points, ratio of closest points, and direction angle between each OSM river centerline and its associated hydroriver. Use the densify tool in ArcGIS to densify the nodes of all hydrorivers and OSM centerlines, setting the densification distance to 100 meters.

[0024] Step 13: Filter OSM centerlines based on the average distance, number of closest points, ratio of closest points, and direction angle, and select OSM centerlines that meet the selection criteria;

[0025] Step 14: After selecting the OSM centerline, sort the centerline corresponding to each hydroriver.

[0026] In any of the above solutions, preferably, the calculation formula of the average distance is:

[0027]

[0028] d min(n) =min(d n,1 ,d n,2 ,……d n,t )

[0029] Among them, D ave is the average distance from an OSM centerline to the corresponding hydroriver, m is the number of nodes in the OSM centerline, n is the node number, d min(n) The shortest distance from node n of the OSM centerline to the hydroriver river, d n,t is the distance from node n of the OSM centerline to node t of the hydroriver.

[0030] In any of the above solutions, it is preferred that the distance d between the two nodes is i,j The calculation method is:

[0031]

[0032] Among them, x i 、y i are the x-coordinate and y-coordinate of node i, respectively. j 、y j are the x-coordinate and y-coordinate of node j respectively.

[0033] In any of the above schemes, it is preferred that for each hydroriver, each node on the river is traversed, all nodes of all associated OSM centerlines are calculated, the nearest point corresponding to each hydroriver node is found, and the OSM centerline where the nearest node is located is recorded, and then the number of nearest nodes on each OSM centerline is summed up to obtain C. near .

[0034] In any of the above solutions, preferably, the closest point ratio P of each OSM center line is near The calculation formula is:

[0035]

[0036] Among them, C total is the total number of nodes on the OSM centerline.

[0037] In any of the above solutions, preferably, the direction angle is calculated as follows:

[0038] Step 121: Calculate the angle of each OSM centerline;

[0039] Step 122: Find the closest nodes on the hydroriver to the first and last nodes on the OSM centerline, record the node numbers as a and b respectively, and calculate the angle of the hydroriver corresponding to the OSM centerline;

[0040] Step 123: Calculate the angle between the OSM centerline and the centerline of the hydroriver;

[0041] Step 124: Control the centerline angle within 90°.

[0042] In any of the above solutions, it is preferred that the angle between each OSM centerline is calculated as follows:

[0043]

[0044] Among them, atan is the inverse cotangent function in trigonometric function, x start 、y start are the x and y coordinates of the first node on the OSM centerline, x end 、y end is the x and y coordinates of the last node on the OSM center line. end =x start When A osm =90°.

[0045] In any of the above solutions, it is preferred that the calculation formula for the angle of the hydroriver corresponding to the OSM centerline is:

[0046]

[0047] Among them, x a 、y a are the x and y coordinates of the node numbered a on the hydroriver. b 、y b are the x and y coordinates of the node numbered b on the hydroriver. a =x b When A osm =90°.

[0048] In any of the above solutions, preferably, the calculation formula of the centerline angle is:

[0049] A diff =|A osm -A hydro |

[0050] When A diff When ≥360°, A diff =A diff -360°;

[0051] When 360°≥A diff >180°, A diff =360°-A diff ;

[0052] When 180°≥A diff >90°, A diff =180°-A diff ;

[0053] When 90°≥A diff >0°, A diff =A diff .

[0054] In any of the above schemes, it is preferred that the selection condition is

[0055] D ave <1000 and C near >50 and P near >0.4 and A diff <20°.

[0056] In any of the above schemes, preferably, step 14 includes calculating the number of the node from each OSM centerline to the nearest hydroriver river node, calculating the average value of the node number on the hydroriver river corresponding to the node of each OSM centerline, and sorting the OSM centerlines from large to small according to the average value.

[0057] In any of the above solutions, preferably, step 2 includes the following sub-steps:

[0058] Step 21: Eliminate the hydroriver sections that do not need to be merged;

[0059] Step 22: For the hydroriver sections that require coordinate modification, modify the coordinates of each node one by one;

[0060] Step 23: Find the nearest OSM centerline node in the order of the nodes of the hydroriver section.

[0061] In any of the above solutions, preferably, step 21 includes calculating the shortest distance d between all nodes of each hydroriver section and the nodes of the associated multiple OSM centerlines. min , when d min When it is >2000, it is determined that the node cannot find the nearest node.

[0062] In any of the above schemes, preferably, step 21 also includes if there are more than 20 nodes at the front end or the back end of a hydroriver section and the nearest node cannot be found, then it is determined that the section does not need to be modified and the node coordinates are not modified.

[0063] In any of the above solutions, preferably, step 22 includes numbering the nodes on the OSM centerline associated with the hydroriver, with the numbering sequence increasing from upstream to downstream.

[0064] In any of the above solutions, preferably, step 23 includes determining that the closest point is found when the distance between the two points is less than 2000, and processing according to the following two situations:

[0065] Case 1: If the code2 of the OSM centerline node found is continuous with the code1 of the OSM centerline node found by the previous hydroriver node, that is, code2=code1 or code2-code1=1, then the coordinates of the hydroriver section node are replaced with the coordinates of the OSM centerline node.

[0066] Case 2: If the number code2 of the found OSM center point is not continuous with the number code1 of the OSM centerline node found by the previous HydroRiver node, that is, code2-code1>1, then add the OSM centerline nodes from code1+1 to code2-1 to the HydroRiver section, and replace the coordinates of the HydroRiver section node with the coordinates of the code2 node.

[0067] In any of the above schemes, preferably, step 3 includes traversing each river section in the hydroriver, and when there is a situation where one adjacent river section has its coordinates modified and the other has not, moving the endpoint of the modified river section to the endpoint of the unmodified river section.

[0068] In any of the above solutions, preferably, step 4 includes calculating the change in length of each river section before and after modification, using the formula:

[0069] L diff =|L new -L orgin |

[0070]

[0071] in, L diff is the absolute value of the length change of the river before and after modification, L ratio The length change ratio of the river before and after modification, L new is the modified length, L orgin The length before modification.

[0072] In any of the above schemes, it is preferred that when L diff >2000 or L ratio When the error is >0.2, it is determined that the changes before and after the restoration are beyond expectations. A comparison check is then performed using high-definition remote sensing images to determine whether the modified river matches the river in the remote sensing image. If the modification result does not match the remote sensing image, manual restoration is performed based on the topological relationship and in combination with the remote sensing image.

[0073] The present invention proposes a multi-resolution river network spatial data fusion and assimilation method, which improves the spatial resolution of river data while maintaining the topological relationship of the river network.

[0074] HydroRIVERS is a global river network data project developed by the World Wildlife Fund (WWF) in collaboration with several international organizations. It aims to provide high-precision river network data through satellite and terrain data analysis.

[0075] OSM, the OpenStreetMap dataset, is an open source global collaborative map project. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 The present invention is a flowchart of a preferred embodiment of the multi-resolution river network spatial data fusion and assimilation method.

[0077] Figure 2The present invention is a flowchart of another preferred embodiment of the multi-resolution river network spatial data fusion and assimilation method. DETAILED DESCRIPTION

[0078] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0079] Example 1

[0080] like Figure 1 As shown, a multi-resolution river network spatial data fusion and assimilation method executes step 1000 to extract river segments from the hydroriver dataset and integrate them into complete rivers, including the following sub-steps:

[0081] Execute step 1010 to save the river segments from hydroriver in a separate layer, where the river is divided into multiple segments.

[0082] Execute step 1020 to integrate the river sections into a complete river based on the confluence relationship of the river sections. The river section integration method includes tracing back upstream from the terminal river section to the upstream source river section, accumulating the total length from each source river section to the terminal river section, and integrating all river sections from the source river section with the largest total length to the terminal river section into a complete river.

[0083] Step 1020 includes the following sub-steps:

[0084] Execute step 1021 to take all river sections flowing into the river as new terminal river sections and integrate them according to the river section integration method to obtain all first-level rivers;

[0085] Execute step 1022 to take all river sections flowing into the first-level river as new terminal river sections, and integrate them according to the river section integration method to obtain all second-level rivers;

[0086] Execute step 1023, taking the river sections flowing into the secondary rivers as the terminal rivers, and integrate them according to the river section integration method to obtain all the third-level rivers;

[0087] Executing step 1024, integrating all river sections into a complete river according to the river section integration method;

[0088] Execute step 1025, after completing the integration of all rivers, use the code of the source river section as the code of the river.

[0089] Executing step 1100 to select the OSM river centerline associated with each hydroriver from the OSM river centerline layer includes the following substeps:

[0090] Execute step 1110 to create a 5 km buffer using each complete hydroriver river, and select the OSM river centerline that intersects the buffer as the candidate river centerline for the river.

[0091] Execute step 1120 to calculate the average distance, number of closest points, ratio of closest points, and direction angle between each OSM river centerline and its associated hydroriver. Use the densify tool in ArcGIS to densify the nodes of all hydrorivers and OSM centerlines, setting the densification distance to 100 meters.

[0092] The calculation formula of the average distance is:

[0093]

[0094] d min(n) =min(d n,1 ,d n,2 ,……d n,t )

[0095] Among them, D ave is the average distance from an OSM centerline to the corresponding hydroriver, m is the number of nodes in the OSM centerline, n is the node number, d min(n) The shortest distance from node n of the OSM centerline to the hydroriver river, d n,t is the distance from node n of the OSM centerline to node t of the hydroriver.

[0096] The distance d between two nodes i,j The calculation method is:

[0097]

[0098] Among them, x i 、y i are the x-coordinate and y-coordinate of node i, respectively. j 、y j are the x-coordinate and y-coordinate of node j respectively.

[0099] For each hydroriver, traverse each node on the river, calculate all the nodes of all the associated OSM centerlines, find the nearest point corresponding to each hydroriver node, and record the OSM centerline where the nearest node is located. Then, summarize the number of nearest nodes on each OSM centerline C. near .

[0100] The closest point ratio P of each OSM center line near The calculation formula is:

[0101]

[0102] Among them, C total is the total number of nodes on the OSM centerline.

[0103] The calculation method of the direction angle is:

[0104] Execute step 1121 to calculate the angle of each OSM center line. The calculation formula is:

[0105]

[0106] Among them, atan is the inverse cotangent function in trigonometric function, x start 、y start are the x and y coordinates of the first node on the OSM centerline, x end 、y end is the x and y coordinates of the last node on the OSM center line. end =x start When A osm =90°.

[0107] Execute step 1122 to find the closest nodes on the hydroriver to the first and last nodes on the OSM centerline. Record the node numbers as a and b respectively. Calculate the angle of the hydroriver corresponding to the OSM centerline using the following formula:

[0108]

[0109] Among them, x a 、y a are the x and y coordinates of the node numbered a on the hydroriver. b 、y b are the x and y coordinates of the node numbered b on the hydroriver. a =x b When A osm =90°

[0110] Execute step 1123 to calculate the angle between the OSM centerline and the centerline of the hydroriver. The calculation formula is:

[0111] A diff =|A osm -A hydro |.

[0112] Execute step 1124 to control the center line angle within 90 degrees.

[0113] When Adiff When ≥360°, A diff =A diff -360°;

[0114] When 360°≥A diff >180°, A diff =360°-A diff ;

[0115] When 180°≥A diff >90°, A diff =180°-A diff ;

[0116] When 90°≥A diff >0°, A diff =A diff .

[0117] Execute step 1130 to filter the OSM center lines based on the average distance, the number of closest points, the closest point ratio, and the direction angle, and filter out the OSM center lines that meet the selection conditions. The selection conditions are:

[0118] D ave <1000 and C near >50 and P near >0.4 and A diff <20°.

[0119] Execute step 1140. After selecting the OSM centerline, sort the centerlines corresponding to each hydroriver, including calculating the number of the node from each OSM centerline to the nearest hydroriver node, calculating the average value of the node number on the hydroriver corresponding to each OSM centerline node, and sorting the OSM centerlines from large to small according to the average value.

[0120] Executing step 1200 to merge the OSM river centerline coordinates into the hydroriver river includes the following sub-steps:

[0121] Execute step 1210 to remove the hydroriver sections that do not need to be merged, including calculating the closest distance d between all nodes of each hydroriver section and the nodes of the associated multiple OSM centerlines. min , when d min When it is >2000, it is determined that the node cannot find the nearest node; if there are more than 20 nodes at the front or back end of a hydroriver section and the nearest node cannot be found, it is determined that the section does not need to be modified and the node coordinates are not modified.

[0122] Execute step 1220 to modify the coordinates of each node of the hydroriver section that needs to have its coordinates modified, including numbering the nodes on the OSM centerline associated with the hydroriver, with the numbering order increasing from upstream to downstream.

[0123] Execute step 1230, and search for the nearest OSM centerline node in the order of the nodes of the hydroriver section. When the distance between the two points is less than 2000, it is determined that the nearest point has been found. The following two cases are processed:

[0124] Case 1: If the code2 of the OSM centerline node found is continuous with the code1 of the OSM centerline node found by the previous hydroriver node, that is, code2=code1 or code2-code1=1, then the coordinates of the hydroriver section node are replaced with the coordinates of the OSM centerline node.

[0125] Case 2: If the number code2 of the found OSM center point is not continuous with the number code1 of the OSM centerline node found by the previous HydroRiver node, that is, code2-code1>1, then add the OSM centerline nodes from code1+1 to code2-1 to the HydroRiver section, and replace the coordinates of the HydroRiver section node with the coordinates of the code2 node.

[0126] Execute step 1300 to repair the topological relationship of each hydroriver, including traversing each river section in the hydroriver. When one adjacent river section has its coordinates modified and the other has not, move the endpoint of the modified river section to the endpoint of the unmodified river section.

[0127] Execute step 1400 to screen and manually repair abnormal river sections, including calculating the length change of each river section before and after modification, using the formula:

[0128] L diff =|L new -L orgin |

[0129]

[0130] in, L diff is the absolute value of the length change of the river before and after modification, L ratio The length change ratio of the river before and after modification, L new is the modified length, Lorgin The length before modification.

[0131] When L diff >2000 or L ratio When the error is >0.2, it is determined that the changes before and after the restoration are beyond expectations. A comparison check is then performed using high-definition remote sensing images to determine whether the modified river matches the river in the remote sensing image. If the modification result does not match the remote sensing image, manual restoration is performed based on the topological relationship and in combination with the remote sensing image.

[0132] Example 2

[0133] This paper proposes a method for fusing and assimilating river data from different sources. While maintaining the topological relationship of the river network, it improves the spatial resolution of river data. It uses multiple constraints such as spatial distance and topological relationship to determine the similarity of rivers, and then uses multiple distances to achieve the fusion of rivers with different resolutions.

[0134] like Figure 2 As shown in FIG, a multi-resolution river network spatial data fusion and assimilation method includes the following steps:

[0135] In the first step, river segments are extracted from the hydroriver dataset and integrated into complete rivers.

[0136] First, save the river segments from hydroriver in a separate layer, in which the river is divided into many segments;

[0137] Next, river segments are integrated into complete rivers based on their confluence relationships. Specifically, trace back upstream from the terminal segment (the most downstream section of a river, typically where it flows into the sea, a lake, or an inland river) to the upstream source segment. Each terminal segment thus corresponds to multiple source segments. The total length from each source segment to the terminal segment is accumulated, and the segments from the source segment with the largest total length to the terminal segment are integrated into a complete first-level river. Next, all river segments that flow into the first-level river are used as new terminal segments, and the same method is used to obtain all second-level rivers. Finally, river segments that flow into the second-level river are used as terminal segments to obtain all third-level rivers. This method continues to integrate all river segments into complete rivers. After all rivers are integrated, the source segment code is used as the river code.

[0138] Finally, sort all river segments of each complete river in the layer from upstream to downstream. The source segment is the first segment, the inflow segment is the second segment, and so on until the end of the river.

[0139] In the second step, the river centerline associated with each hydroriver is selected from the OSM river centerline layer.

[0140] First, a 5 km buffer zone was created using each complete hydroriver, and the OSM river centerline that intersected with the buffer zone was selected as the candidate river centerline for the river.

[0141] Secondly, the average distance, number of closest points, proportion of closest points, and direction angle between each OSM river centerline and its associated hydroriver were calculated.

[0142] Using the densify tool of ArcGIS, all hydroriver rivers and OSM center lines were densified, and the densification distance was set to 100 meters.

[0143] (1) Average distance

[0144]

[0145] d min(n) =min(d n,1 ,d n,2 ,……d n,t )

[0146] Where D ave It represents the average distance from an OSM centerline to the corresponding hydroriver; m represents the number of nodes in the OSM centerline, n represents the node number, d min(n) The shortest distance from node n of the OSM centerline to the hydroriver; d n,t Indicates the distance from node n of the OSM centerline to node t of the hydroriver.

[0147] The distance between two nodes is calculated as:

[0148]

[0149] Where x i 、y i Represents the x-coordinate and y-coordinate of the i-node, respectively. j 、y j Represent the x-coordinate and y-coordinate of node j respectively.

[0150] (2) Number of closest points

[0151] For each hydroriver, we traverse each node on the river, calculate all the nodes of all the OSM centerlines associated with it, find the nearest point corresponding to each hydroriver node, and record the OSM centerline where the nearest node is located. Then we summarize the number of nearest nodes on each OSM centerline (C near ).

[0152] (3) Proportion of closest point

[0153] Calculate the nearest node ratio for each OSM centerline.

[0154]

[0155] Where C near Indicates the number of nearest nodes on the OSM centerline, C total Indicates the total number of nodes on this OSM centerline.

[0156] (4) Direction angle

[0157] First, calculate the angle of each OSM centerline

[0158]

[0159] In the formula, atan is the inverse cotangent function in trigonometric function, x start 、y start Indicates the x and y coordinates of the first node on the OSM centerline, x end 、y end Indicates the x, y coordinates of the last node on the OSM centerline. end =x start , A osm =90.

[0160] Find the closest nodes on the hydroriver to the first and last nodes on the OSM centerline, numbering them a and b respectively. Calculate the angle of the hydroriver relative to the OSM centerline.

[0161]

[0162] In the formula, atan is the inverse cotangent function in trigonometric function, x a 、y a Indicates the x and y coordinates of the node numbered a on the hydroriver. b 、y b Indicates the x and y coordinates of the node numbered b on the hydroriver. a =x b , then A osm =90.

[0163] Calculate the angle between the OSM centerline and the hydroriver centerline.

[0164] A diff =|A osm -A hydro|

[0165] Then perform the following three steps in sequence to control the angle within 90 degrees:

[0166] If A diff >360,A diff =A diff -360;

[0167] If A diff >180,A diff =360-A diff ;

[0168] If A diff >90,A diff =180-A diff .

[0169] OSM centerlines are filtered based on the average distance, number of closest points, ratio of closest points, and direction angle. The OSM centerlines that meet the following conditions are selected:

[0170] D ave <1000 and C near >50 and P near >0.4 and A diff <20

[0171] After selecting the OSM centerlines, sort the centerlines corresponding to each hydroriver. This is done by calculating the number of the node on each OSM centerline to the nearest hydroriver node (since the hydroriver sections are sorted, the numbers increase from upstream to downstream). Then, the average number of the hydroriver node corresponding to each OSM centerline node is calculated, and the OSM centerlines are sorted from largest to smallest based on the average number.

[0172] The third step is to merge the OSM centerline coordinates into the hydroriver.

[0173] To preserve the topology of the HydroRiver and integrate the high-precision OSM centerline into the HydroRiver, the HydroRiver nodes were moved to the nearest OSM centerline node. This was done by processing each HydroRiver segment individually.

[0174] First, remove the hydroriver sections that do not need to be merged. Calculate the closest distance d between all nodes of each hydroriver section and the nodes of the associated multiple OSM centerlines. min , if dmin If the node coordinates are greater than 2000, the node is considered to have no nearest node. If there are more than 20 nodes at the front or back end of a hydroriver section that cannot find the nearest node, the section is considered to not need to be modified and no node coordinates will be modified later.

[0175] Secondly, for the hydroriver sections that need coordinate modification, modify the coordinates of each node one by one. Before modification, number the nodes on the OSM centerline associated with the hydroriver, with the numbering order increasing from upstream to downstream.

[0176] According to the node order of the hydroriver section, the nearest OSM centerline node is searched in turn. If the distance between the two points is less than 2000, it is considered that the nearest point is found, and then the processing is divided into two cases:

[0177] The first case: If the number (code2) of the OSM centerline node found is continuous with the number (code1) of the OSM centerline node found by the previous hydroriver node (code2=code1 or code2-code1=1), the coordinates of the hydroriver section node are replaced with the coordinates of the OSM centerline node.

[0178] Second case: If the number of the found OSM center point (code2) is not continuous with the number of the OSM centerline node (code1) found by the previous HydroRiver node (code2-code1>1), then add the OSM centerline nodes from code1+1 to code2-1 to the HydroRiver section, and replace the coordinates of the HydroRiver section node with the coordinates of the code2 node.

[0179] The fourth step is to repair the topological relationship of each hydroriver.

[0180] Traverse each river section in the hydroriver. If there is a situation where one of the adjacent river sections has its coordinates modified and the other has not, move the endpoint of the modified river section to the endpoint of the unmodified river section to ensure the connectivity of the two river sections.

[0181] Step 5: Screen and manually repair abnormal river sections.

[0182] Calculate the change in length of each river section before and after modification:

[0183] L diff =|L new -L orgin |

[0184]

[0185] Where, L new Indicates the modified length, L orgin Indicates the length before modification, in meters.

[0186] If L diff >2000 or L ratio If the value is >0.2, it is considered that the changes before and after the restoration are large and the river section needs to be checked. If the modification is unreasonable, manual restoration is performed based on the topological relationship and combined with remote sensing images.

[0187] In order to better understand the present invention, the above is described in detail in conjunction with the specific embodiments of the present invention, but it is not intended to limit the present invention. Any simple modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention. Each embodiment in this specification focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referred to each other. For the system embodiment, since it basically corresponds to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

Claims

1. A multi-resolution river network spatial data fusion and assimilation method, comprising extracting river segments from a hydroriver dataset and integrating them into complete rivers, characterized in that: The following steps are also included: Step 1: Select the OSM river centerline associated with each hydroriver from the OSM river centerline layer, including the following substeps: Step 11: Create a 5km buffer using each complete hydroriver, and select the OSM river centerline that intersects the buffer as the candidate river centerline for the river. Step 12: Calculate the average distance, number of closest points, ratio of closest points, and direction angle between each OSM river centerline and its associated hydroriver. Use the densify tool in ArcGIS to densify the nodes of all hydrorivers and OSM centerlines, setting the densification distance to 100 meters. Step 13: Filter OSM centerlines based on the average distance, number of closest points, ratio of closest points, and direction angle, and select OSM centerlines that meet the selection criteria; Step 14: After selecting the OSM centerline, sort the centerline corresponding to each hydroriver; Step 2: Merge the OSM river centerline coordinates into the hydroriver river; Step 3: Repair the topological relationship of each hydroriver; Step 4: Screen and manually repair abnormal river sections.

2. The multi-resolution river network spatial data fusion and assimilation method according to claim 1, characterized in that: Extracting river segments from the hydroriver dataset and integrating them into complete rivers includes the following sub-steps: Step 01: Save the river segments from HydroRiver in a separate layer. The river is divided into many segments in this layer. Step 02: Integrate the river sections into complete rivers based on their confluence relationships.

3. The multi-resolution river network spatial data fusion and assimilation method according to claim 2 is characterized in that: The river section integration method includes tracing back upstream from the terminal river section to the upstream source river section, accumulating the total length of each source river section to the terminal river section, and integrating all river sections from the source river section with the largest total length to the terminal river section into a complete river.

4. The multi-resolution river network spatial data fusion and assimilation method according to claim 3 is characterized in that: Step 02 includes the following sub-steps: Step 021: All river sections flowing into the river are taken as new terminal river sections and integrated according to the river section integration method to obtain all first-level rivers; Step 022: All river sections flowing into the first-level river are taken as new terminal river sections and integrated according to the river section integration method to obtain all second-level rivers; Step 023: The river sections flowing into the secondary rivers are regarded as the terminal rivers, and are integrated according to the river section integration method to obtain all the third-level rivers; Step 024: Integrate all river sections into a complete river according to the river section integration method; Step 025: After all rivers are integrated, the code of the source river section is used as the code of the river.

5. The multi-resolution river network spatial data fusion and assimilation method according to claim 4 is characterized in that: The calculation formula of the average distance is: ， the min(n) =min(d n,1 ,d n,2 ,……d n,t ) Among them, D ave is the average distance from an OSM centerline to the corresponding hydroriver, m is the number of nodes in the OSM centerline, n is the node number, d min(n) The shortest distance from node n of the OSM centerline to the hydroriver river, d n,t is the distance from node n of the OSM centerline to node t of the hydroriver.

6. The multi-resolution river network spatial data fusion and assimilation method according to claim 5, characterized in that: The distance d between two nodes i,j The calculation method is: ， Among them, x i 、y i are the x-coordinate and y-coordinate of node i, respectively. j 、y j are the x-coordinate and y-coordinate of node j respectively.

7. The multi-resolution river network spatial data fusion and assimilation method according to claim 6, characterized in that: For each hydroriver, traverse each node on the river, calculate all the nodes of all the associated OSM centerlines, find the nearest point corresponding to each hydroriver node, and record the OSM centerline where the nearest node is located. Then, summarize the number of nearest nodes on each OSM centerline C. near .

8. The multi-resolution river network spatial data fusion and assimilation method according to claim 7, characterized in that: The closest point ratio P of each OSM center line near The calculation formula is: ， Among them, C total is the total number of nodes on the OSM centerline.

9. The multi-resolution river network spatial data fusion and assimilation method according to claim 8, characterized in that: The calculation method of the direction angle is: Step 121: Calculate the angle of each OSM centerline; Step 122: Find the closest nodes on the hydroriver to the first and last nodes on the OSM centerline, record the node numbers as a and b respectively, and calculate the angle of the hydroriver corresponding to the OSM centerline; Step 123: Calculate the angle between the OSM centerline and the centerline of the hydroriver; Step 124: Control the centerline angle within 90°.

10. The multi-resolution river network spatial data fusion and assimilation method according to claim 9, characterized in that: The calculation formula for the angle of each OSM center line is: ， Among them, atan is the inverse cotangent function in trigonometric function, x start 、y start are the x and y coordinates of the first node on the OSM centerline, x end 、y end is the x and y coordinates of the last node on the OSM center line. end =x start When A osm =90°.

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