Method and system for mutually converting elevation map and bathymetric map, and storage medium

Abstract

The invention discloses an elevation map and bathymetric map mutual conversion method and system, and the method comprises the steps: obtaining dynamic waterline information and water level information in real time, correcting the dynamic waterline information and the water level information to obtain a corrected instantaneous waterline, and unifying the corrected instantaneous waterline to an elevation point on a target moment waterline; constructing a first Delaunay triangulation network according to the elevation points on the waterline; dividing the first map into an underwater topographic map and a shore topographic map by taking the corrected instantaneous waterline at the target moment as a segmentation line; based on the underwater topographic map, extracting an underwater first point map layer; the first point diagram layer is superposed in the first Delaunay triangulation network; calculating second points corresponding to the first points in the triangular mesh in the first Delaunay triangulation network one by one by adopting an interpolation algorithm; according to the second point, constructing a second Delaunay triangulation network, generating a second line, and further obtaining a corresponding terrain; and superposing the corresponding terrain and the shore topographic map to generate a second map, thereby realizing efficient and accurate conversion.

Description

Technical Field

[0001] The present invention relates to the field of geographic information system and hydrological measurement technology, and in particular to a method, system and storage medium for converting elevation map and water depth map. Background Art

[0002] In hydrological surveying, elevation maps and bathymetry maps are two commonly used and core two-dimensional representations of three-dimensional data. The elevation map represents the height information of the land surface, while the bathymetry map reflects the depth information from the bottom of the water body to the water surface. In some specific application scenarios, it is necessary to convert the elevation map into a bathymetry map, or convert the bathymetry map into an elevation map. Traditional conversion methods usually require a lot of manual operations, have low conversion efficiency, do not consider real-time water level changes, and are prone to introduce errors. It is difficult to solve the conversion between elevation maps and bathymetry maps with large riverbed gradients. Especially when facing scenes with steep changes in the riverbed or complex terrain, this conversion becomes particularly difficult, which is not only time-consuming and labor-intensive, but also has poor accuracy and efficiency.

[0003] With the development of computer technology and automation systems, some software tools and algorithms have been developed to support these conversions, but most of them rely on precise input data and complex mathematical models. When faced with large-scale and wide-ranging topographic map data processing and conversion, especially in areas with large riverbed gradients, the lateral gradient of the water surface on the left and right banks is ignored, resulting in unsatisfactory conversion efficiency and accuracy. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the traditional method of converting between elevation map and water depth map requires a lot of manual operation, has low conversion efficiency, is prone to introduce errors, and has low real-time and accuracy. It is particularly difficult to adapt to the conversion problem when the riverbed changes steeply or in complex terrain scenes. The purpose of the present invention is to provide a method, system and storage medium for converting between elevation map and water depth map. The present invention effectively utilizes the terrain data processing advantages of the Delaunay triangulation algorithm, solves the problems of low efficiency and inaccuracy of traditional manual conversion, achieves more efficient and accurate conversion, and demonstrates its stability and applicability in a variable terrain environment.

[0005] The present invention is achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for converting an elevation map to a depth map, the method comprising:

[0007] The dynamic water edge information and water level information are obtained in real time, and correction is performed based on the dynamic water edge information and water level information to obtain the corrected instantaneous water edge and unify it to the elevation point on the water edge at the target time;

[0008] According to the elevation points on the waterside line, the first Delaunay triangulation is constructed; the construction form of the first Delaunay triangulation can reflect the actual curvature and direction of the waterside;

[0009] Preprocessing the first image to be converted, unifying the data format and layer attributes of the first point data in the first image; and dividing the first image into an underwater topographic map and a shore topographic map by using the instantaneous water edge line corrected at the target time as a dividing line;

[0010] Based on the underwater topographic map, extract the first point layer underwater; and superimpose the first point layer onto the first Delaunay triangulation; the first point layer is the collection of all first points;

[0011] The interpolation algorithm is used to calculate the second point corresponding to the first point in the triangle mesh of the first Delaunay triangulation one by one;

[0012] According to the second point, a second Delaunay triangulation is constructed, and a second line is generated; according to the second point and the second line, a corresponding terrain is obtained;

[0013] The corresponding topography is superimposed on the onshore topographic map to generate a second map.

[0014] Further, if the first map is an elevation map, the first point is an elevation point, the second point is a water depth point, and the second line is a water depth line, then the second map is a water depth map.

[0015] Further, if the first map is a water depth map, the first point is a water depth point, the second point is an elevation point, and the second line is an isobath, then the second map is an elevation map.

[0016] Furthermore, the dynamic water edge information and water level information are acquired in real time, and correction is performed based on the dynamic water edge information and water level information, including:

[0017] Real-time acquisition of dynamic waterside information through an unmanned aerial vehicle system; the unmanned aerial vehicle system is configured with a high-precision GPS, an IMU sensor, a camera or a laser radar, and a wireless communication module;

[0018] Obtaining real-time water level information through a hydrological station; the hydrological station is equipped with a water level sensor, a data acquisition and transmission module;

[0019] Synchronize the dynamic water edge information with the real-time water level information to ensure that the corresponding time points of the two are consistent;

[0020] The real-time water level data is applied to the dynamic water edge information to correct the water edge position; the Geographic Information System (GIS) software is used to fuse and process the data to generate the corrected instantaneous water edge.

[0021] Furthermore, the first Delaunay triangulation includes a number of river-crossing triangles, and the three vertices in each river-crossing triangle satisfy the following conditions:

[0022] Two of the vertices are on the left bank waterline, the third vertex should be on the right bank waterline, and each vertex is constructed in a preset rule order;

[0023] Or two of the vertices are on the right bank waterline, and the third vertex is on the left bank waterline, and the vertices are constructed in sequence according to a preset rule.

[0024] Furthermore, the interpolation algorithm is used to calculate the water depth points corresponding to the elevation points in the triangular mesh in the first Delaunay triangulation one by one, including:

[0025] Retrieve and identify local elevation points and the first Delaunay triangulation;

[0026] By calculating the distance and ray intersection, it is determined whether the projection point of the elevation point is inside the first Delaunay triangulation. The determination method is: each triangle mesh of the first Delaunay triangulation is regarded as a closed area, and the transformation point is determined whether it is inside the triangle according to the projection coordinates of the transformation point in the plane, so as to determine the first Delaunay triangle required for the transformation point.

[0027] If yes, then use the interpolation algorithm to calculate the water depth point value H at the projection point P; make a ray AP through the projection point P and the vertex A of the triangle mesh, and intersect the line segment BC at point O; the line segment BC is the line formed between the vertex B and the vertex C of the triangle mesh; the interpolation calculation formula of the water depth point value H is:

[0028] H=H1+(H3+(H3-H2)*L2 / (L1+L2)-H1)*d1 / (d1+d2)

[0029] Among them, H1, H2, and H3 are the elevation values ​​(vertical coordinates) corresponding to the vertices A, B, and C of the triangle mesh respectively; d1 and d2 are the lengths of the line segments PA and PO respectively; L1 and L2 are the lengths of the line segments BO and CO respectively.

[0030] Furthermore, the method further comprises:

[0031] The second line is filtered and smoothed using a step-size equal-division mean wave removal method.

[0032] Further, filtering and smoothing the second line includes:

[0033] Identify the obvious bending feature points of the second line to obtain the obvious bending feature points;

[0034] Segmenting the second line according to the obvious bending feature points to obtain a segmented second line;

[0035] Input the filtering step size, select all the second lines after segmentation and traverse, perform wave removal on each second line after segmentation, generate new multi-line segments and delete the source multi-line segments;

[0036] The number of equally divided segments is determined by calculating the length of the polyline segment and the step size; based on the number of equally divided segments, a point set is obtained and a new polyline segment is created as the processed second line.

[0037] In a second aspect, the present invention further provides a system for converting an elevation map to a water depth map, the system using the above-mentioned method for converting an elevation map to a water depth map; the system comprises:

[0038] Information acquisition unit, used to obtain dynamic water edge information and water level information in real time,

[0039] The instantaneous water edge correction unit is used to correct the instantaneous water edge based on the dynamic water edge information and the water level information, obtain the corrected instantaneous water edge and unify it to the elevation point on the water edge at the target time;

[0040] The first Delaunay triangulation construction unit is used to construct the first Delaunay triangulation according to the elevation points on the waterside line; the construction form of the first Delaunay triangulation can reflect the actual curvature and direction of the waterside;

[0041] A first image preprocessing unit, used for preprocessing the first image to be converted, and unifying the data format and layer attributes of the first point data in the first image;

[0042] a segmentation unit, for dividing the first image into an underwater topographic map and a shore topographic map by taking the instantaneous water edge line corrected at the target moment as a segmentation line;

[0043] The first point extraction and superposition unit is used to extract the first underwater point layer based on the underwater topographic map; and superimpose the first point layer into the first Delaunay triangulation network; the first point layer is a collection of all first points;

[0044] A second point calculation unit is used to calculate the second point corresponding to the first point in the triangular mesh of the first Delaunay triangulation one by one by using an interpolation algorithm;

[0045] A second Delaunay triangulation construction unit is used to construct a second Delaunay triangulation according to the second point and generate a second line; and obtain a corresponding terrain according to the second point and the second line;

[0046] The second map generating unit is used to superimpose the corresponding terrain with the onshore terrain map to generate a second map.

[0047] In a third aspect, the present invention further provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the above-mentioned method for converting between an elevation map and a depth map.

[0048] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0049] 1. The present invention provides a method, system and storage medium for converting elevation maps to depth maps. The present invention realizes efficient and high-precision conversion between depth maps and elevation maps by introducing two Delaunay triangulation constructions. The first time, a special cross-river Delaunay triangulation is introduced to calculate the converted depth points with a single cross-river triangle as the calculation unit; the second time, the Delaunay triangulation is reconstructed based on all the converted depth points to generate depth lines. The present invention solves the problems of low efficiency and inaccuracy of traditional manual conversion, realizes more efficient and accurate conversion, and demonstrates its stability and applicability in variable terrain environments.

[0050] 2. The present invention provides a method, system and storage medium for converting elevation maps and water depth maps. By utilizing the real-time water level information of the UAV system and the hydrological station and combining the existing terrain information of the old map (i.e., the elevation map or water depth map to be converted), the planar position of the instantaneous water edge line and the instantaneous water level information are corrected for the target water level information, thereby greatly improving the real-time performance and accuracy of the conversion between the elevation map and the water depth map. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0052] Figure 1 A flow chart of a method for converting an elevation map to a depth map according to the present invention;

[0053] Figure 2 A detailed flow chart of converting an elevation map to a water depth map according to the present invention;

[0054] Figure 3 The present invention is a certain time t B Flowchart for obtaining the instantaneous water edge at any moment;

[0055] Figure 4 It is a characteristic schematic diagram of the first Delaunay triangulation of the present invention;

[0056] Figure 5 It is a schematic diagram of calculating the water depth value H at the projection point P when the projection point P is on a triangular polyline according to the present invention;

[0057] Figure 6A schematic diagram of the present invention showing that a point P is projected inside a triangular polyline and a water depth value H at the projected point P is calculated;

[0058] Figure 7 The image data (a) acquired by the drone system of the present invention, the point cloud data (b) acquired by the drone system, and the extracted instantaneous water edge information (c);

[0059] Figure 8 Schematic diagram of the instantaneous water edge of the present invention (the blue line is 2021 / 12 / 01 10:00; the cyan line is 2021 / 12 / 01 14:00; the green line is 2021 / 12 / 01 18:00);

[0060] Fig. 9 The instantaneous water edge line schematic diagram is corrected according to the contour lines of the old map and the aerial point cloud data of the present invention;

[0061] Fig.10 The present invention uses the instantaneous water level at the target time (2021 / 12 / 01 14:00) as the dividing line to divide the old map before conversion into the onshore part A and the underwater part B; (a) is the onshore part A (i.e., the onshore topographic map), and (b) is the underwater part B (i.e., the underwater topographic map);

[0062] Fig.11 Schematic diagram of the construction and superposition of the first Delaunay triangulation of the present invention, (a) is the construction of the first Delaunay triangulation, (b) is the superposition of the underwater elevation and the first Delaunay triangulation;

[0063] Fig.12 Schematic diagram of the construction of the first Delaunay triangulation and the second Delaunay triangulation and the superposition of isobaths (unfiltered) and water depth points of the present invention, (a) schematic diagram of the superposition of the first Delaunay triangulation and the calculated water depth points, (b) construction of the second Delaunay triangulation, (c) schematic diagram of the superposition of isobaths (unfiltered) and water depth points;

[0064] Fig.13 This is the depth map result after conversion by the present invention (2021 / 12 / 01 14:00);

[0065] Fig.14 The present invention is a structural block diagram of a system for converting elevation maps and water depth maps. DETAILED DESCRIPTION

[0066] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0067] The traditional and commonly used method of converting elevation map (water depth map) to water depth map (elevation map) is to divide the interval with a small difference in water level into a polygonal area, divide the interval to be converted into several polygonal intervals, and take the average water level in the polygonal interval as the water surface height of the area, subtract the bottom elevation (water depth value), and convert the area into each polygonal block to obtain the water depth point (elevation point). The traditional method of converting elevation map to water depth map requires a lot of manual operation, has low conversion efficiency, does not consider the real-time water level change, and inevitably introduces water depth (underwater elevation) conversion errors, resulting in low conversion precision and accuracy; in particular, it is difficult to adapt to the conversion problem at a specific target time when the riverbed changes steeply or in complex terrain scenes. With the development of computer technology and automation systems, although some software tools and algorithms have been developed to support these conversions, most of them rely on accurate input data and complex mathematical models. When facing large-scale and large-scale terrain map data processing and conversion, especially when converting in areas with large riverbed gradients, the horizontal gradient of the water surface on the left and right banks is ignored, resulting in low conversion efficiency and accuracy.

[0068] Therefore, considering that Delaunay triangulation network is a mathematical algorithm, its advantage is that it can efficiently process spatial coordinate point data and construct a triangulated network, and digital terrain modeling often uses this algorithm to generate a three-dimensional grid model of the terrain. The present invention takes into account the advantages of Delaunay triangulation network in processing irregular and complex terrain data, efficient spatial data indexing and fast neighborhood search, and designs a method for converting elevation maps and water depth maps to solve the shortcomings of the prior art, achieve more efficient and more accurate conversion, and show its stability and applicability in a variable terrain environment.

[0069] The present invention realizes the efficient and high-precision conversion between the water depth map and the elevation map by introducing the construction of two Delaunay triangulations. The first time, a special cross-river Delaunay triangulation is introduced to calculate the converted water depth points (or underwater elevation points) with a single cross-river triangle as the calculation unit; the second time, the Delaunay triangulation is reconstructed based on all the converted water depth points (underwater elevation points), and then the water depth lines (isodepth lines) are generated; and then the obvious bending feature points on the water depth lines (isodepth lines) are obtained as the segment nodes of the polyline, and the water depth lines (isodepth lines) are smoothed by the step-length equal-division mean wave removal method. The method fully considers factors such as the longitudinal water level change and the horizontal gradient of the river, and solves the problems of the longitudinal water level change and the horizontal gradient of the river by constructing a Delaunay triangulation: at the bend of the river or the area with large terrain undulations, the Delaunay triangulation can generate triangles that are more in line with the actual terrain, thereby more accurately simulating the longitudinal water level change. The horizontal gradient can be accurately calculated in the cross-river Delaunay triangle according to the elevations of different positions on the left and right banks. In addition, by utilizing the real-time water level information from the drone system and the hydrological station and combining it with the existing terrain information from the old map (i.e. the elevation map or depth map to be converted), the target water level information is corrected for the plane position of the instantaneous water edge and the instantaneous water level information, which greatly improves the real-time and accuracy of the conversion of the elevation map (depth map) to the depth map (elevation map).

[0070] Example 1

[0071] like Figure 1 As shown, the present invention provides a method for converting an elevation map and a water depth map, the method comprising:

[0072] The dynamic water edge information and water level information are obtained in real time, and correction is performed based on the dynamic water edge information and water level information to obtain the corrected instantaneous water edge and unify it to the elevation point on the water edge at the target time;

[0073] According to the elevation points on the waterside line, the first Delaunay triangulation is constructed; the construction form of the first Delaunay triangulation can reflect the actual curvature and direction of the waterside;

[0074] Preprocessing the first image to be converted, unifying the data format and layer attributes of the first point data in the first image; and dividing the first image into an underwater topographic map and a shore topographic map by using the instantaneous water edge line corrected at the target time as a dividing line;

[0075] Based on the underwater topographic map, extract the first point layer underwater; and superimpose the first point layer onto the first Delaunay triangulation; the first point layer is the collection of all first points;

[0076] The interpolation algorithm is used to calculate the second point corresponding to the first point in the triangle mesh of the first Delaunay triangulation one by one;

[0077] According to the second point, a second Delaunay triangulation is constructed, and a second line is generated; according to the second point and the second line, a corresponding terrain is obtained;

[0078] The corresponding topography is superimposed on the onshore topographic map to generate a second map.

[0079] Specifically, the conversion between elevation map and depth map includes:

[0080] First, convert the elevation map to a depth map, that is, if the first map is an elevation map, and the first point is an elevation point, the second point is a depth point, and the second line is a depth line, then the second map is a depth map. Figure 2 As shown, the execution flow of this method is:

[0081] The dynamic water edge information and water level information are obtained in real time, and correction is performed based on the dynamic water edge information and water level information to obtain the corrected instantaneous water edge and unify it to the elevation point on the water edge at the target time;

[0082] According to the elevation points on the waterside line, the first Delaunay triangulation is constructed; the construction form of the first Delaunay triangulation can reflect the actual curvature and direction of the waterside;

[0083] Preprocess the elevation map to be converted, unify the data format and layer attributes of the existing elevation point data in the elevation map; and use the instantaneous water edge line corrected at the target time as the dividing line to divide the elevation map to be converted into an underwater topographic map and a shore topographic map;

[0084] Based on the underwater topographic map, extract the underwater elevation point layer; and superimpose the elevation point layer into the first Delaunay triangulation; the elevation point layer is a collection of all elevation points;

[0085] The interpolation algorithm is used to calculate the water depth points corresponding to the elevation points in the triangular mesh of the first Delaunay triangulation one by one;

[0086] According to the water depth points, the second Delaunay triangulation is constructed and the water depth lines are generated; according to the water depth points and water depth lines, the corresponding terrain is obtained;

[0087] The corresponding topography is superimposed on the onshore topographic map to generate a bathymetric map.

[0088] Second, convert the water depth map to an elevation map, that is, if the first map is a water depth map, and the first point is a water depth point, the second point is an elevation point, and the second line is an isobath, then the second map is an elevation map. The execution process of this method is:

[0089] The dynamic water edge information and water level information are obtained in real time, and correction is performed based on the dynamic water edge information and water level information to obtain the corrected instantaneous water edge and unify it to the elevation point on the water edge at the target time;

[0090] According to the elevation points on the waterside line, the first Delaunay triangulation is constructed; the construction form of the first Delaunay triangulation can reflect the actual curvature and direction of the waterside;

[0091] Preprocess the depth map to be converted, unify the data format and layer attributes of the existing depth point data in the depth map; and use the instantaneous water edge line corrected at the target time as the dividing line to divide the depth map into an underwater topographic map and an onshore topographic map;

[0092] Based on the underwater topographic map, extract the underwater water depth point layer; and superimpose the water depth point layer on the first Delaunay triangulation; the water depth point layer is a collection of all water depth points;

[0093] The interpolation algorithm is used to calculate the elevation points corresponding to the water depth points in the triangular mesh of the first Delaunay triangulation one by one;

[0094] According to the elevation points, the second Delaunay triangulation is constructed and the isobaths are generated; according to the elevation points and isobaths, the corresponding terrain is obtained;

[0095] The corresponding terrain is superimposed on the onshore topographic map to generate an elevation map.

[0096] In this embodiment, the dynamic water edge information and water level information are acquired in real time, and correction is performed based on the dynamic water edge information and water level information, including:

[0097] Real-time acquisition of dynamic waterside information through an unmanned aerial vehicle system; the unmanned aerial vehicle system is configured with a high-precision GPS, an IMU sensor, a camera or a laser radar, and a wireless communication module;

[0098] Obtaining real-time water level information through a hydrological station; the hydrological station is equipped with a water level sensor, a data acquisition and transmission module;

[0099] Synchronize the dynamic water edge information with the real-time water level information to ensure that the corresponding time points of the two are consistent;

[0100] The real-time water level data is applied to the dynamic water edge information to correct the water edge position; the Geographic Information System (GIS) software is used to fuse and process the data to generate the corrected instantaneous water edge.

[0101] Specifically, (1) the dynamic waterside information is obtained in real time through the UAV system; the UAV system is equipped with high-precision GPS, IMU sensors, high-resolution cameras or laser radars and wireless communication modules; specifically, high-precision GPS and IMU sensors are used to ensure accurate positioning and attitude data; high-resolution cameras or laser radars are used to obtain detailed data on terrain and waterside; and wireless communication modules (such as 4G / 5G networks) can be used to transmit waterside data (images or laser point clouds) back to the ground station in real time. In specific implementation, 1) flight mission planning. ① According to the target area, the flight path of the UAV is planned to ensure coverage of the entire waterside area. ② The flight altitude and speed are set to ensure the accuracy and efficiency of data collection. 2) Data collection. The UAV flies along the predetermined path and collects terrain and waterside data in real time. Using real-time image processing algorithms, waterside information is identified and extracted. 3) Data transmission and processing. The waterside data is transmitted back to the ground station in real time through a wireless communication module (such as 4G / 5G networks). Preliminary data processing is performed at the ground station to generate a dynamic waterside.

[0102] (2) Obtain water level information in real time through the hydrological station; the hydrological station is equipped with a water level sensor and a data acquisition and transmission module; specifically, the water level sensor is used to monitor water level changes in real time; the data acquisition and transmission module is used to ensure the continuous acquisition and real-time transmission of real-time water level data, and the water level data can be transmitted to a central server or ground station through wireless communication (such as LoRa, NB-IoT or 4G / 5G).

[0103] When implementing it, Figure 3 As shown, the UAV system obtains a certain t A The image (including water edge information) and point cloud data at the time; the water level station acquisition includes at least t A ,t B Real-time water level information at all times;

[0104] t B Time to t A The elevation correction coefficient △ at time t B Time to t A The instantaneous water edge elevation correction coefficient △ at the moment;

[0105] Through the instantaneous water edge elevation correction coefficient △ correction, UAV point cloud and old map data correction t B The instantaneous water edge and the elevation points on the water edge at the moment.

[0106] In this embodiment, preprocessing of the first image to be converted includes noise filtering, format conversion, unit unification, etc.

[0107] In this embodiment, the interpolation algorithm adopts linear interpolation method, and the instantaneous water edge line is discretely added with elevation points according to the real-time water level information. The elevation points on the instantaneous water edge line should be able to reflect the curved shape characteristics of the water edge line. If the characteristic points are missing, the water edge elevation point P2 is interpolated based on the previous water edge elevation point P1 and the next water edge elevation point P3; the formula of linear interpolation method is:

[0108]

[0109] Among them, P1 (X1, Y1, H1) is the three-dimensional coordinate of the elevation point P1, X1, Y1, H1 are the ordinate, abscissa and ordinate of point P1 respectively; P2 (X2, Y2, H2) is the three-dimensional coordinate of the elevation point P2, X2, Y2, H2 are the ordinate, abscissa and ordinate of point P2 respectively; P3 (X3, Y3, H3) is the three-dimensional coordinate of the elevation point P3, X3, Y3, H3 are the ordinate, abscissa and ordinate of point P3 respectively.

[0110] In this embodiment, the construction of the first Delaunay triangulation is based on the Southern cass10.1, and can basically reflect the curvature of the waterside line. Figure 4 The features shown are that the first Delaunay triangulation includes a number of river-crossing triangles, and the three vertices in each river-crossing triangle meet the following conditions:

[0111] Two of the vertices are on the left bank waterline, the third vertex should be on the right bank waterline, and each vertex is constructed in a preset rule order;

[0112] Or two of the vertices are on the right bank waterline, and the third vertex is on the left bank waterline, and the vertices are constructed in sequence according to a preset rule.

[0113] The triangles of the first Delaunay triangulation constructed above should be river-crossing triangles.

[0114] In this embodiment, the interpolation algorithm is used to calculate the water depth points corresponding to the elevation points in the triangular mesh in the first Delaunay triangulation one by one, including:

[0115] (1) Retrieve and identify local elevation points and the first Delaunay triangulation;

[0116] (2) By calculating the distance and ray intersection, determine whether the projection point of the elevation point is inside the first Delaunay triangulation. The determination method is: regard each triangle mesh of the first Delaunay triangulation as a closed area, and determine whether the transformation point is inside the triangle according to the projection coordinates of the transformation point in the plane, so as to determine the first Delaunay triangle required for the transformation point.

[0117] Determine whether a point is inside a polyline by calculating distance and ray intersection, etc. Loop through the triangulation set (tv2). The specific algorithm is used to determine whether a point P is on (inside) a closed triangle polyline.

[0118] A. First determine that point P is on the closed triangular polyline. Assume the triangle △ABC, with endpoints A(x1, y1), B(x2, y2), and B(x3, y3).

[0119] ①For side AB

[0120]

[0121] ②For edge BC

[0122]

[0123] ②For edge CA

[0124]

[0125] Check whether the point is on the line segment of the edge: Even if the distance between the point and an edge is zero, it is necessary to ensure that the point P is within the range of the line segment of the edge.

[0126] For side AB, determine whether point P is within the line segment of AB:

[0127] min(x1,x2)≤x≤max(x1,x2)

[0128] min(y1,y2)≤y≤max(y1,y2)

[0129] First, check whether the two-dimensional distance from the point to the closed triangle polyline is small enough. If so, return true.

[0130] The same process is performed for edges BC and CA.

[0131] If the distance from point P to an edge is zero and satisfies the line segment range condition of the edge, then point P is on the polyline of the triangle.

[0132] In the case of a triangular polyline, calculate the water depth H at the point P, such as Figure 5 shown.

[0133] H=H2+(H3-H1)*d2 / (d1+d2)

[0134] Where d1 and d2 are the line segment lengths of PA and PB respectively.

[0135] B. If point P is determined to be inside the closed triangle polyline, set the Z coordinate of the point to 0, and create two rays Ray1 and Ray2, one along the positive direction and the other along the negative direction of the X axis.

[0136] By obtaining the number of intersections between these two rays and the triangle polyline.

[0137] If the number of these two intersection points is an odd number, the point is considered to be inside the triangle polyline, otherwise it is outside the triangle polyline.

[0138] Inside the triangular polyline, calculate the water depth H at the point P, such as Figure 6 shown.

[0139] A ray AP is made through the projection point P and the vertex A of the triangular mesh, intersecting the line segment BC at point O; the line segment BC is the line formed between the vertex B and the vertex C of the triangular mesh; the interpolation calculation formula of the water depth point value H is:

[0140] H=H1+(H3+(H3-H2)*L2 / (L1+L2)-H1)*d1 / (d1+d2)

[0141] Among them, H1, H2, and H3 are the elevation values ​​(vertical coordinates) corresponding to the vertices A, B, and C of the triangle mesh respectively; d1 and d2 are the lengths of the line segments PA and PO respectively; L1 and L2 are the lengths of the line segments BO and CO respectively.

[0142] As a further implementation, the method further comprises:

[0143] The second line is filtered and smoothed using a step-size equal-division mean de-wavy method.

[0144] Specifically, filtering and smoothing the second line includes:

[0145] Identifying obvious bending feature points of the second line to obtain obvious bending feature points;

[0146] Segmenting the second line according to the obvious bending feature points to obtain a segmented second line;

[0147] Input the filtering step size, select all the second lines after segmentation and traverse, perform wave removal on each second line after segmentation, generate new multi-line segments and delete the source multi-line segments;

[0148] The number of equally divided segments is determined by calculating the length and step size of the multi-line segment; based on the number of equally divided segments, a point set is obtained and a new multi-line segment is created as the processed second line.

[0149] In specific implementation, this embodiment provides a case of converting an elevation map to a water depth map based on a Delaunay triangulation network. The specific implementation steps are as follows:

[0150] 1. Obtain dynamic waterside information in real time through the UAV system (such as Figure 7 (a) Image data obtained by the UAV system) and real-time water level information of the hydrological station (Table 1), and the real-time instantaneous water edge ( Figure 7 (b)).

[0151] Table 1 Water level information data in the region of the embodiment

[0152] Equipment No. Site Name Collection time Original water level (m) Elevation water level (m) WJGL0000011 **Water level 2021-12-01 00:00:00 0.842 594.317 WJGL0000011 **Water level 2021-12-01 00:35:00 0.944 594.419 WJGL0000011 **Water level 2021-12-01 01:00:00 1.017 594.492 WJGL0000011 **Water level 2021-12-01 01:30:00 1.114 594.589 WJGL0000011 **Water level 2021-12-01 02:00:00 1.21 594.685 WJGL0000011 **Water level 2021-12-01 02:35:00 1.314 594.789 WJGL0000011 **Water level 2021-12-01 03:00:00 1.387 594.862 WJGL0000011 **Water level 2021-12-01 04:00:00 1.445 594.92 WJGL0000011 **Water level 2021-12-01 05:00:00 1.409 594.884 WJGL0000011 **Water level 2021-12-01 06:00:00 1.305 594.78 WJGL0000011 **Water level 2021-12-01 06:40:00 1.2 594.675 WJGL0000011 **Water level 2021-12-01 07:00:00 1.16 594.635 WJGL0000011 **Water level 2021-12-01 07:45:00 1.065 594.54 WJGL0000011 **Water level 2021-12-01 08:00:00 1.035 594.51 WJGL0000011 **Water level 2021-12-01 09:00:00 1.017 594.492 WJGL0000011 **Water level 2021-12-01 09:15:00 0.908 594.383 WJGL0000011 **Water level 2021-12-01 10:00:00 0.866 594.341 WJGL0000011 **Water level 2021-12-01 11:00:00 0.828 594.303 WJGL0000011 **Water level 2021-12-01 12:00:00 0.782 594.257 WJGL0000011 **Water level 2021-12-01 13:00:00 0.76 594.235 WJGL0000011 **Water level 2021-12-01 14:00:00 0.714 594.189 WJGL0000011 **Water level 2021-12-01 15:00:00 0.692 594.167 WJGL0000011 **Water level 2021-12-01 16:00:00 0.693 594.168 WJGL0000011 **Water level 2021-12-01 17:00:00 0.688 594.163 WJGL0000011 **Water level 2021-12-01 18:00:00 0.682 594.157 WJGL0000011 **Water level 2021-12-01 19:00:00 0.674 594.149 WJGL0000011 **Water level 2021-12-01 20:00:00 0.674 594.149 WJGL0000011 **Water level 2021-12-01 21:00:00 0.714 594.189 WJGL0000011 **Water level 2021-12-01 22:00:00 0.803 594.278 WJGL0000011 **Water level 2021-12-01 23:00:00 0.89 594.365

[0153] The assumption is to take the instantaneous water edge at 2021 / 12 / 01 14:00 and 2021 / 12 / 01 18:00.

[0154] From Table 1 above, we can see that the water level information data of a hydrological station within a certain range of the region is 594.341 meters at 10:00 on 2021 / 12 / 01, 594.189 meters at 14:00 on 2021 / 12 / 01, and 594.157 meters at 18:00 on 2021 / 12 / 01. It can be obtained that the elevation correction coefficient from 14:00 on 2021 / 12 / 01 to 10:00 on 2021 / 12 / 01 is △h1=594.189-594.341=-0.152, and the elevation correction coefficient from 18:00 on 2021 / 12 / 01 to 10:00 on 2021 / 12 / 01 is △h2=594.157-594.341=-0.184. The instantaneous water edge at 2021 / 12 / 01 14:00 and 2021 / 12 / 01 18:00 was corrected with reference to the original old map data and the elevation correction coefficient. The correction results are: Fig. 9 shown.

[0155] 2. Data preprocessing: First, obtain the elevation data of the area to be converted (i.e. the elevation map to be converted). These data can come from field measurements, remote sensing acquisition, or existing geographic information databases. If the data contains noise, it needs to be filtered, and necessary format conversion and unit unification are required.

[0156] 3. Extract underwater data and onshore data separately. Use the instantaneous water level at the target time (2021 / 12 / 01 14:00) as the dividing line to divide the old map before conversion into the onshore part A, the underwater part B, the reference water edge line and the elevation point on the water edge line as C. Fig.10 As shown, (a) is the onshore part A (i.e., the onshore topographic map), and (b) is the underwater part B (i.e., the underwater topographic map).

[0157] 4. Construction of the first Delaunay triangulation and superposition of underwater elevation and triangulation: Using the reference water edge and the elevation point on the water edge, i.e., C, the first Delaunay triangulation of the water edge is constructed. Fig.11 As shown, (a) is the construction of the first Delaunay triangulation of part C, and (b) is the superposition of the underwater elevation and the first Delaunay triangulation.

[0158] 5. Calculate elevation or water depth. Calculate elevation points based on the constructed first Delaunay triangulation. At this point, each triangular mesh is regarded as a small plane, and the elevation point values ​​of unknown points in the mesh are calculated using the interpolation algorithm based on the elevation data of known points on the plane.

[0159] 6. Construct the second Delaunay triangulation and generate the second line (isodepth line). Construct the second Delaunay triangulation according to the water depth points of each point in the second Delaunay triangulation and draw the isobath using cass software. Fig.12 shown.

[0160] 7. Smooth the water depth line. Combine the transformed underwater part and the shore part into a whole to get a complete water depth map, such as Fig.13 shown.

[0161] Example 2

[0162] like Fig.14 As shown, the difference between this embodiment and embodiment 1 is that this embodiment provides a system for converting an elevation map to a water depth map, and the system uses a method for converting an elevation map to a water depth map in embodiment 1; the system corresponds one-to-one to a method for converting an elevation map to a water depth map in embodiment 1; the system includes:

[0163] Information acquisition unit, used to obtain dynamic water edge information and water level information in real time,

[0164] The instantaneous water edge correction unit is used to correct the instantaneous water edge based on the dynamic water edge information and the water level information, obtain the corrected instantaneous water edge and unify it to the elevation point on the water edge at the target time;

[0165] The first Delaunay triangulation construction unit is used to construct the first Delaunay triangulation according to the elevation points on the waterside line; the construction form of the first Delaunay triangulation can reflect the actual curvature and direction of the waterside;

[0166] A first image preprocessing unit, used for preprocessing the first image to be converted, and unifying the data format and layer attributes of the first point data in the first image;

[0167] a segmentation unit, for dividing the first image into an underwater topographic map and a shore topographic map by taking the instantaneous water edge line corrected at the target moment as a segmentation line;

[0168] The first point extraction and overlay unit is used to extract the first underwater point layer based on the underwater topographic map (if the number of underwater elevation points is too small to accurately and detailedly express the underwater topography, the underwater topographic points should be encrypted or the points of the underwater contour lines (which should have elevation value attributes) should be extracted as the first point layer); and the first point layer is overlaid on the first Delaunay triangulation network; the first point layer is the collection of all first points;

[0169] A second point calculation unit is used to calculate the second point corresponding to the first point in the triangular mesh of the first Delaunay triangulation one by one by using an interpolation algorithm;

[0170] A second Delaunay triangulation construction unit is used to construct a second Delaunay triangulation according to the second point and generate a second line; and obtain a corresponding terrain according to the second point and the second line;

[0171] The second map generating unit is used to superimpose the corresponding terrain with the onshore terrain map to generate a second map.

[0172] Among them, the execution process of each unit can be executed according to the process steps of a method for converting an elevation map and a water depth map in Example 1, and will not be repeated one by one in this embodiment.

[0173] At the same time, the present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the above-mentioned method for converting between an elevation map and a water depth map.

[0174] The present invention not only greatly saves manpower and reduces workload, but also can more accurately reflect the real underwater terrain depth information compared with traditional methods, especially in scenes with complex river terrain and undulating seabed. In addition, the present invention improves the automation level of map conversion, reduces the influence of human errors, and improves the reliability and accuracy of data processing.

[0175] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0176] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0177] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0178] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0179] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for converting an elevation map to a depth map, characterized in that: The method includes: Acquire dynamic water edge information and water level information in real time, perform correction based on the dynamic water edge information and water level information, obtain a corrected instantaneous water edge and unify it to the elevation point on the water edge at the target time; Constructing a first Delaunay triangulation according to the elevation points on the waterside line; the construction form of the first Delaunay triangulation can reflect the actual curvature and direction of the waterside; Preprocessing the first image to be converted, unifying the data format and layer attributes of the first point data in the first image; and dividing the first image into an underwater topographic map and a shore topographic map by using the instantaneous water edge line corrected at the target time as a dividing line; Based on the underwater topographic map, extract a first underwater point layer; and superimpose the first point layer onto a first Delaunay triangulation network; the first point layer is a collection of all first points; The interpolation algorithm is used to calculate the second point corresponding to the first point in the triangle mesh of the first Delaunay triangulation one by one; According to the second point, a second Delaunay triangulation is constructed, and a second line is generated; according to the second point and the second line, a corresponding terrain is obtained; The corresponding terrain is superimposed on the shore terrain map to generate a second map.

2. A method for converting an elevation map to a depth map according to claim 1, characterized in that: If the first map is an elevation map, the first point is an elevation point, the second point is a depth point, and the second line is a depth line, then the second map is a depth map.

3. A method for converting an elevation map to a depth map according to claim 1, characterized in that: If the first map is a bathymetric map, the first point is a bathymetric point, the second point is an elevation point, and the second line is a depth contour line, then the second map is an elevation map.

4. A method for converting an elevation map to a depth map according to claim 1, characterized in that: Acquiring dynamic water edge information and water level information in real time, and making corrections based on the dynamic water edge information and water level information, including: Real-time acquisition of dynamic waterside information through an unmanned aerial vehicle system; the unmanned aerial vehicle system is configured with a high-precision GPS, an IMU sensor, a camera or a laser radar, and a wireless communication module; Obtaining real-time water level information through a hydrological station; the hydrological station is equipped with a water level sensor, a data acquisition and transmission module; Synchronize the dynamic water edge information with the real-time water level information to ensure that the corresponding time points of the two are consistent; The real-time water level data is applied to the dynamic water edge information to correct the water edge position; the geographic information system software is used to fuse and process the data to generate the corrected instantaneous water edge.

5. The method for converting an elevation map to a depth map according to claim 1, characterized in that: The first Delaunay triangulation includes a plurality of river-crossing triangles, and the three vertices of each river-crossing triangle satisfy the following conditions: Two of the vertices are on the left bank waterline, the third vertex should be on the right bank waterline, and each vertex is constructed in a preset order; Or two of the vertices are on the right bank waterline, and the third vertex is on the left bank waterline, and the vertices are constructed in sequence according to a preset rule.

6. A method for converting an elevation map to a depth map according to claim 2, characterized in that: The interpolation algorithm is used to calculate the water depth points corresponding to the elevation points in the triangular mesh in the first Delaunay triangulation one by one, including: Retrieve and identify local elevation points and the first Delaunay triangulation; By calculating the distance and the ray intersection method, it is determined whether the projection point of the elevation point is inside the first Delaunay triangulation; If yes, then use the interpolation algorithm to calculate the water depth point value H at the projection point P; make a ray AP through the projection point P and the vertex A of the triangle mesh, and intersect the line segment BC at point O; the line segment BC is the line formed between the vertex B and the vertex C of the triangle mesh; the interpolation calculation formula of the water depth point value H is: H=H1+(H3+(H3-H2)*L2 / (L1+L2)-H1)*d1 / (d1+d2) Among them, H1, H2, and H3 are the elevation values ​​corresponding to the vertices A, B, and C of the triangle mesh respectively; d1 and d2 are the lengths of the line segments PA and PO respectively; L1 and L2 are the lengths of the line segments BO and CO respectively.

7. The method for converting an elevation map to a depth map according to claim 1, characterized in that: The method further includes: The second line is subjected to filtering and smoothing processing, and the filtering and smoothing processing adopts a step-size equal-division mean de-wavy method.

8. A method for converting an elevation map to a depth map according to claim 7, characterized in that: The second line is subjected to filtering and smoothing processing, comprising: Identify the obvious bending feature points of the second line to obtain the obvious bending feature points; Segmenting the second line according to the obvious bending feature points to obtain a segmented second line; Input the filtering step size, select all the second lines after segmentation and traverse, perform wave removal on each second line after segmentation, generate new multi-line segments and delete the source multi-line segments; The number of equally divided segments is determined by calculating the length of the multi-line segment and the step size; based on the number of equally divided segments, a point set is obtained and a new multi-line segment is created as the processed second line.

9. A system for converting elevation maps to depth maps, characterized in that: The system includes: Information acquisition unit, used to obtain dynamic water edge information and water level information in real time, An instantaneous water edge correction unit is used to perform correction based on the dynamic water edge information and water level information to obtain a corrected instantaneous water edge and unify it to an elevation point on the water edge at a target moment; A first Delaunay triangulation construction unit is used to construct a first Delaunay triangulation according to the elevation points on the waterside line; the construction form of the first Delaunay triangulation can reflect the actual curvature and direction of the waterside; A first image preprocessing unit, used for preprocessing the first image to be converted, and unifying the data format and layer attributes of the first point data in the first image; a segmentation unit, for dividing the first image into an underwater topographic map and a shore topographic map by taking the instantaneous water edge line corrected at the target moment as a segmentation line; A first point extraction and superposition unit is used to extract a first underwater point layer based on the underwater topographic map; and superimpose the first point layer into a first Delaunay triangulation network; the first point layer is a collection of all first points; A second point calculation unit is used to calculate the second point corresponding to the first point in the triangular mesh of the first Delaunay triangulation one by one by using an interpolation algorithm; A second Delaunay triangulation construction unit is used to construct a second Delaunay triangulation according to the second point and generate a second line; and obtain a corresponding terrain according to the second point and the second line; The second map generating unit is used to superimpose the corresponding terrain with the onshore terrain map to generate a second map.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, a method for converting an elevation map and a depth map according to any one of claims 1 to 8 is implemented.

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