A method, system, device and medium for measuring diffraction points of mountain peaks based on digital elevation models

Abstract

A method, system, device and medium for measuring diffraction points of mountain peaks based on digital elevation models. The method includes: obtaining a digital elevation model, a digital three-dimensional terrain model, the three-dimensional coordinate positions of a transmitting antenna with absolute height or relative height, and the three-dimensional coordinate positions of a receiving antenna with absolute height or relative height, and successively obtaining terrain triangular facet element data, a two-dimensional profile contour data array of the undulating terrain between the transmitting antenna and the receiving antenna, higher mountain peak elements, adjacent mountain peak array elements, a mountain peak three-dimensional coordinate array, a mountain peak linked list through data processing or calculation, inserting mountain peak diffraction nodes into the mountain peak linked list to obtain mountain peak diffraction points; the system, device and medium are used to implement a method for measuring diffraction points of mountain peaks based on digital elevation models; the present invention has the characteristics of comprehensive consideration factors, high accuracy and strong universality.

Description

Technical Field

[0001] The present invention relates to the technical field of diffraction point measurement, and particularly relates to a method, system, device and medium for measuring diffraction points of mountain peaks based on a digital elevation model. Background Art

[0002] At present, the survival and activities of human beings are mainly limited to the surface layer of the earth and some spatial ranges around it. As the carrier of radio communication services, radio waves mainly transmit remote information in these spaces. The undulating terrain and landforms on the earth's surface constitute important boundary conditions for the propagation of radio waves in the natural environment. The terrain is divided into different types according to the irregularity of the ground. Different types of propagation mechanisms will occur when radio waves propagate in different types of terrain, which are mainly summarized as reflection, diffraction and scattering of radio waves, etc.

[0003] In the area network corresponding to the point of ground mobile radio communication, most propagation paths are blocked by undulating terrain or landforms within the spatial area of the first Fresnel ellipsoid. There is one or more separate obstacles. The phenomenon that radio waves bypass the obstacles on the propagation path is called diffraction. For obstacles such as prominent terrain and buildings, radio waves will propagate over such obstacles in a diffractive manner. The energy of radio waves will be severely attenuated during the propagation process. Therefore, it is necessary to estimate these obstacle losses.

[0004] In microwave and ultra-short wave communications, the main obstacle often encountered is an isolated mountain peak. If the obstacle is relatively steep and has a certain width laterally, it can be regarded as a knife-edge peak. The diffraction of the knife-edge peak extends infinitely laterally and half a space longitudinally, that is, it is assumed that the obstacle is a semi-infinite absorbing screen. When radio waves are projected onto the screen, no scattering and reflection occur and they will be completely absorbed, and the ridge of the screen is sharp. In actual situations, as a mountain peak acting as a diffraction obstacle, its mountain body is rough or covered with many trees. It can be seen that regardless of the slope and thickness of the mountain body, it can be approximately regarded as an absorbing screen. Therefore, the above assumptions are approximately valid in actual situations, and the mountain peaks in the propagation path of radio waves in undulating terrain can be approximated as knife-shaped mountain peaks for calculating the diffraction mechanism.

[0005] The existing methods for obtaining diffraction points of mountain peaks in a hilly terrain environment mainly rely on field measurements or manual screening with the aid of digital elevation models. This not only wastes manpower and material resources but also has the drawback of large errors during the measurement and screening processes. Moreover, only the terrain and environment on the ground are classified. For the classification of ground obstacles, they are only divided into terrain obstacles such as plains, hills, and mountainous areas based on the degree of terrain undulation. In areas with large ground undulations, such as mountainous and hilly terrains, simply using the degree of terrain undulation for fuzzy classification is not accurate enough and cannot accurately represent the characteristic areas of mountain peaks, valleys, and foothills on the terrain. Therefore, the existing technology lacks completeness in expressing the characteristic areas of hilly terrains and cannot accurately extract the terrain features in irregular hilly terrains when there are obstructions in the radio wave propagation path. For deterministic propagation models, such as those based on ray-tracing algorithms, accurate terrain feature extraction is required for precise terrain modeling to achieve accurate electromagnetic propagation prediction.

[0006] The patent application with the publication number [CN101090301] discloses "A Method for Simulating and Measuring Radio Wave Path Loss". The steps of its measurement method include: inputting a digital map, determining the map matrix and the path loss matrix, and obtaining the propagation model and transmitting antenna parameters; generating a series of layered rays starting from the transmitting antenna according to the transmitting antenna parameters and the range to be measured, taking a series of sampling points on each ray, and determining valid sampling points according to the map grid corresponding to the sampling point positions in the map matrix; calculating the effective height and diffraction loss of the transmitting antenna according to the geographical information corresponding to the positions of the valid sampling points in the map, and calculating the path loss of the valid sampling points in combination with the propagation model; taking the path loss of the valid sampling points as the path loss of the map grid corresponding to the valid sampling points and saving it into the path loss matrix. Since the calculation principle of the knife-edge peaks in this invention is: draw a line from the transmitting antenna to the receiving antenna, and the set of intersection points of this line and the mountain peaks is the set of knife-edge peaks. However, in actual terrain environments, many hilly terrains are irregular, with special protrusions and depressions. Therefore, obtaining knife-edge peaks only through the intersection points of the line connecting the transmitting and receiving antennas and the mountain peaks is not comprehensive. It cannot obtain the true knife-edge peaks in the actual terrain and cannot obtain the valley and foothill features in the terrain either. Therefore, it has the drawbacks of incomplete consideration factors and inaccurate prediction results.

[0007] The patent application with the publication number [CN110677296] discloses "A method for computer simulation of radio wave communication in a single-edge peak terrain", and its method steps include: S1. Load a three-dimensional digital map; S2. Set the positions of a communication transmitter and a receiver on the three-dimensional digital map; S3. Set the operating frequency of the communication devices used by the communication transmitter and the receiver; S4. On the three-dimensional digital map, form a terrain elevation profile between the communication transmitter and the receiver; S5. Determine the single-edge peak terrain according to the three-dimensional digital map and the terrain elevation profile; S6. Calculate the terrain attenuation correction factor A(U); S7. Calculate the free space transmission loss of radio waves; S8. Calculate the radio wave transmission loss according to the terrain attenuation correction factor A(U) and the free space transmission loss; S9. Use the radio wave transmission loss as the attenuation value of the radio wave communication for communication. And the patent application with the publication number [CN110677205] discloses "A method for computer simulation of radio wave communication in a double-peak terrain", and its method steps include: S1. Load a three-dimensional digital map; S2. Set the positions of a communication transmitter and a receiver on the three-dimensional digital map; S3. Set the operating frequency of the communication devices used by the communication transmitter and the receiver; S4. On the three-dimensional digital map, form a terrain elevation profile between the communication transmitter and the receiver; S5. Determine the double-peak terrain according to the three-dimensional digital map and the terrain elevation profile; the double-peak terrain includes a first peak and a second peak; S6. Calculate the terrain attenuation correction factor A(U); S7. Calculate the free space transmission loss of radio waves; S8. Calculate the radio wave transmission loss according to the terrain attenuation correction factor and the free space transmission loss A(U); S9. Use the radio wave transmission loss as the attenuation value of the radio wave communication for simulation communication. Since in the real geographical terrain environment, it is too ideal that there is only a single or double-edge peak terrain. In the point-to-area network of ground mobile radio communication, most propagation paths are usually blocked by multiple individual obstacles within the spatial region of the first Fresnel ellipsoid. Therefore, it has the disadvantages of incomplete consideration factors and inaccurate prediction results.

[0008] The patent application with the publication number [CN110581740] discloses "A method for computer simulation of radio wave communication in irregular terrain", and its method steps include: S1. Load a three-dimensional digital map; S2. Set the positions of the communication transmitter and receiver on the three-dimensional digital map; S3. Set the operating frequency of the communication devices used by the communication transmitter and receiver; S4. On the three-dimensional digital map, form a terrain elevation profile between the communication transmitter and the receiver; S5. Judge the irregular terrain according to the three-dimensional digital map and the terrain elevation profile; S6. Calculate the terrain attenuation correction factor A(U), and step S6 includes the following steps: S61: Introduce a parameter Δh to characterize the degree of terrain irregularity; S62: Establish the relationship between the terrain attenuation correction factor and the distance from the transmitter under different Δh; S63: Calculate the terrain attenuation correction factor A(U); S7. Calculate the free space transmission loss of radio waves; S8. Calculate the radio wave transmission loss; S9. Use the radio wave transmission loss as the attenuation value of radio wave communication for simulated communication. Since in the wireless network planning of the near-ground point-to-area, most propagation paths are blocked by undulating terrain or landforms in the spatial region of the first Fresnel ellipsoid, there are multiple individual obstacles, and it is not accurate enough to make a vague division only by the degree of terrain undulation, and it cannot accurately represent the characteristic areas of mountains, valleys and foothills on the terrain. Therefore, it has the disadvantages of incomplete consideration factors and inaccurate prediction results. Summary of the Invention

[0009] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method, system, device and medium for measuring mountain diffraction points based on a digital elevation model. Through the digital elevation model, the characteristics of valleys and mountains in the real terrain environment are extracted, and the ground height picking function and the two-dimensional profile calculation function are used to extract the refined and multi-level environmental characteristics of the complex terrain environment. According to the extracted characteristic parameters, screening and calculation are carried out to obtain the measurement result of the mountain diffraction point based on the digital elevation model; therefore, it has the characteristics of comprehensive consideration factors, high accuracy rate and strong universality.

[0010] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0011] A method for measuring mountain diffraction points based on a digital elevation model includes the following steps:

[0012] Step 1, obtain the digital elevation model, the digital three-dimensional terrain model, the three-dimensional coordinate position of the transmitting antenna with absolute height or relative height, and the three-dimensional coordinate position of the receiving antenna with absolute height or relative height;

[0013] Step 2, triangulate the digital three-dimensional terrain model obtained in Step 1 according to the grid accuracy to obtain terrain triangle element data;

[0014] Step 3: Calculate the two-dimensional profile contour data array of the undulating terrain between the transmitting antenna and the receiving antenna by using the two-dimensional profile contour calculation function with the terrain triangular facet element data obtained in Step 2, the three-dimensional coordinate positions of the transmitting antenna with absolute height or relative height obtained in Step 1, and the three-dimensional coordinate positions of the receiving antenna with absolute height or relative height.

[0015] Step 4: Compare the elements of the two adjacent two-dimensional profile contour arrays in the two-dimensional profile contour data array of the undulating terrain obtained in Step 3, and filter out the higher mountain peak elements and the adjacent mountain peak array elements.

[0016] Step 5: Calculate, filter, and aggregate the higher mountain peak elements, the adjacent mountain peak array elements obtained in Step 4, the three-dimensional coordinate positions of the transmitting antenna with absolute height or relative height obtained in Step 1, and the three-dimensional coordinate positions of the receiving antenna with absolute height or relative height in sequence to obtain the mountain peak three-dimensional coordinate array.

[0017] Step 6: Based on the mountain peak three-dimensional coordinate array obtained in Step 5, sequentially determine whether there is a new occlusion point between two adjacent mountain peaks. If so, go to Step 7; if not, continue to judge until all mountain peaks are traversed, and obtain the mountain peak linked list by positively looping through the mountain peak three-dimensional coordinate array.

[0018] Step 7: Based on the adjacent mountain peaks with occlusion points obtained in Step 6, obtain the occlusion points existing between two adjacent peaks, that is, the mountain peak diffraction nodes, and insert the mountain peak diffraction nodes into the nodes of the mountain peak linked list to obtain the mountain peak linked list.

[0019] Step 8: Assign the mountain peak linked lists obtained in Step 6 and Step 7 to the mountain peak diffraction path to obtain the mountain peak diffraction points.

[0020] The specific process of Step 1 is as follows: Import the digital elevation model in the format of suffixes.asc and.txt, load the digital elevation model into a digital three-dimensional terrain model representing the undulating terrain simulation environment. In the same coordinate system as the digital three-dimensional terrain model, input the three-dimensional coordinate positions of the transmitting antenna and the receiving antenna, and use the ground height picking function to project the three-dimensional coordinate position (x 1 , y 1 , z 1 ) of the transmitting antenna onto the undulating terrain to obtain the projection point (x 1 , y 1 ) of the current terrain of the transmitting antenna; project the three-dimensional coordinate position (x 2 , y 2 , z 2 ) of the receiving antenna onto the undulating terrain to obtain the projection point (x 2 , y 2), according to the plane equation where the projection points (x 1 , y 1 ) and (x 2 , y 2 ) are located, obtain the height of the terrain plane corresponding to the projection point of the three-dimensional coordinate position. If the three-dimensional coordinate positions of the imported transmitting antenna and receiving antenna are absolute heights, directly proceed to step two; if the three-dimensional coordinate positions of the imported transmitting antenna and receiving antenna are relative heights, then add the relative height to the height of the terrain plane corresponding to the projection point of the three-dimensional coordinate position to obtain the absolute height of the three-dimensional coordinate position, and proceed to step two;

[0021] The ground height pickup function is expressed as:

[0022]

[0023]

[0024] where z 地 is the ground height obtained on the ground, and x TRI , y TRI and z TRI are the three-dimensional coordinates of the right-angled vertex of the triangular element, is the normal vector of the triangular element where it is located, and x 地 , y 地 are the coordinates of the projection point projected onto the triangular element;

[0025] The plane equation is expressed as:

[0026] A×(x TRI -x 地 ) + B×(y TRI -y 地 ) + C×(z TRI -z 地 ) = 0

[0027]

[0028] where, is the normal vector of the triangular element where it is located, and x TRI , y TRI and z TRI are the three-dimensional coordinates of the right-angled vertex of the triangular element, and x 地 , y 地 and z 地 are the three-dimensional coordinates of any point on the triangular element except the vertex.

[0029] The specific process of the second step is to traverse the grid nodes in the digital three-dimensional terrain model obtained in the first step row by row. Two adjacent grid nodes in two adjacent rows of data form the four three-dimensional coordinate vertices of a grid, namely DEM[i][j], DEM[i + 1][j], DEM[i][j + 1], and DEM[i + 1][j + 1]. Among them, three three-dimensional coordinate vertices can form a triangular facet. The triangular facets are stored in clockwise order, that is: DEM[i][j], DEM[i + 1][j], and DEM[i][j + 1] or DEM[i + 1][j], DEM[i + 1][j + 1], and DEM[i][j + 1]. All the triangular facets are sorted first by row and then by column to obtain the terrain triangular facet data.

[0030] The specific process of the third step is to use the two-dimensional profile calculation function with the terrain triangular facet data obtained in the second step, the three-dimensional coordinate position of the transmitting antenna with absolute height or relative height obtained in the first step, and the three-dimensional coordinate position of the receiving antenna with absolute height or relative height. A unit vector is established, that is, starting from the transmitting antenna, traversing to the receiving antenna at a fixed step along the direction from the transmitting antenna to the receiving antenna, and sequentially obtaining the height of the terrain plane where each step projection point is located. Each step projection point and its corresponding terrain height are combined into three-dimensional coordinates (x i , y i , z i ) and stored in order to obtain the two-dimensional profile data array of the undulating terrain between the transmitting antenna and the receiving antenna;

[0031] The two-dimensional profile calculation function is expressed as:

[0032] For the case where the slope formed by the projection points of the transmitting antenna and the receiving antenna does not exist, that is, x 发射天线 = x 接收天线 , y 发射天线 ≠ y 接收天线 :

[0033]

[0034] Among them, x i , y i and z i are the three-dimensional coordinate points of the two-dimensional profile, i is the index number of the three-dimensional coordinate points of the two-dimensional profile, f(x i , y i ) is the ground height picking function, step is the fixed step for traversing along the direction from the transmitting antenna to the receiving antenna, x 发射天线 , y 发射天线 are the coordinates of the projection point of the transmitting antenna, x 接收天线 , y 接收天线The projection point coordinates of the transmitting antenna;

[0035] For the case where the slope formed by the projection point of the transmitting antenna and the projection point of the receiving antenna is 0, i.e., x 发射天线 ≠x 接收天线 , y 发射天线 =y 接收天线 :

[0036]

[0037] where x i , y i and z i are the three-dimensional coordinate points of the two-dimensional profile, i is the index number of the three-dimensional coordinate points of the two-dimensional profile, f(x i , y i ) is the ground height picking function, step is the fixed step length traversed along the direction from the transmitting antenna to the receiving antenna, x 发射天线 , y 发射天线 are the projection point coordinates of the transmitting antenna, x 接收天线 , y 接收天线 are the projection point coordinates of the transmitting antenna;

[0038] For the case where the slope formed by the projection point of the transmitting antenna and the projection point of the receiving antenna exists and is not 0, i.e., x 发射天线 ≠x 接收天线 , y 发射天线 ≠y 接收天线 :

[0039]

[0040]

[0041]

[0042] where x i , y i and z i are the three-dimensional coordinate points of the two-dimensional profile, i is the index number of the three-dimensional coordinate points of the two-dimensional profile, f(x i , y i ) is the ground height picking function, step is the fixed step length traversed along the direction from the transmitting antenna to the receiving antenna, k is the slope formed by the projection point of the transmitting antenna and the projection point of the receiving antenna, x 发射天线 , y 发射天线 are the projection point coordinates of the transmitting antenna, x 接收天线 , y 接收天线 are the projection point coordinates of the transmitting antenna.

[0043] The specific process of the fourth step is as follows: According to the two-dimensional profile contour data array of the undulating terrain obtained in the third step, compare adjacent two-dimensional profile contour array elements, and judge whether the current element is a peak value. If it is, store the current element into the mountain peak value array; if not, the current element is a valley value element, and delete the valley value element; judge whether the distance between two peak value array elements stored in the mountain peak value array is greater than the search spacing. If it is, retain the higher mountain peak value element; if not, retain the adjacent mountain peak value array elements.

[0044] The specific process of the fifth step is as follows: Use the higher mountain peak value elements obtained in the fourth step, the adjacent mountain peak value array elements, the three-dimensional coordinate positions of the transmitting antenna with absolute height or relative height and the three-dimensional coordinate positions of the receiving antenna with absolute height or relative height obtained in the first step, and calculate using the obstacle point clearance calculation formula to obtain the obstacle point clearance. Judge whether the mountain peak obstacle point clearance between the transmitting antenna and the receiving antenna is greater than zero. If it is, retain the current mountain peak value element; if not, remove the current mountain peak value element, and collect the retained current mountain peak value elements in order to obtain the mountain peak three-dimensional coordinate array.

[0045] The calculation formula for the obstacle point clearance is as follows:

[0046]

[0047] Where K is the equivalent earth radius coefficient; d T is the ground distance from the transmitting antenna to the knife-edge obstacle mountain peak, with the unit of km; d R is the ground distance from the receiving antenna to the knife-edge obstacle mountain peak, with the unit of km; d is the ground distance from the transmitting antenna to the receiving antenna, with the unit of km; h T is the altitude of the transmitting antenna, with the unit of m; h R is the altitude of the receiving antenna, with the unit of m; h is the altitude of the knife-edge obstacle mountain peak, with the unit of m.

[0048] A mountain peak diffraction point measurement system based on a digital elevation model includes:

[0049] A terrain loading module: used to load the digital elevation model into a digital three-dimensional terrain model representing an undulating terrain simulation environment;

[0050] A terrain triangular facet meshing module: used to perform triangular facet meshing on the digital three-dimensional terrain model according to the grid accuracy to obtain terrain triangular facet data;

[0051] An antenna height setting module: used to obtain the three-dimensional coordinate positions of the transmitting antenna with absolute height or relative height and the three-dimensional coordinate positions of the receiving antenna with absolute height or relative height;

[0052] Two-dimensional profile calculation module: It is used to obtain the two-dimensional profile data array of the undulating terrain between the transmitting antenna and the receiving antenna by using the two-dimensional profile calculation function based on the terrain triangular element data, the three-dimensional coordinate position of the transmitting antenna with absolute height or relative height, and the three-dimensional coordinate position of the receiving antenna with absolute height or relative height;

[0053] Mountain peak element acquisition and screening module: It is used to compare two adjacent elements of the two-dimensional profile array, determine whether the current element is a peak value. If so, store the current element into the mountain peak value array; if not, the current element is a valley value element, and delete the valley value element; determine whether the distance between two peak value array elements stored in the mountain peak value array is greater than the search spacing. If so, retain the higher mountain peak element; if not, retain the adjacent mountain peak array elements;

[0054] Diffraction point screening module: It is used to calculate the obstacle point clearance by using the obstacle point clearance calculation formula for the obtained higher mountain peak elements, adjacent mountain peak array elements, the three-dimensional coordinate position of the transmitting antenna with absolute height or relative height, and the three-dimensional coordinate position of the receiving antenna with absolute height or relative height, and determine whether the mountain peak obstacle point clearance between the transmitting antenna and the receiving antenna is greater than zero. If so, retain the current mountain peak element; if not, remove the current mountain peak element, and order and set the retained current mountain peak elements to obtain the mountain peak three-dimensional coordinate array;

[0055] Terrain occlusion judgment module: It is used to judge whether there is a new occlusion point between two adjacent peaks. If there is an occlusion point, obtain the occlusion point, that is, the mountain peak diffraction node, and store the mountain peak diffraction node into the mountain peak linked list to obtain a new mountain peak linked list; if there is no occlusion point, judge whether the mountain peaks have been traversed. If the mountain peaks have been traversed, output the mountain peak diffraction path; if the mountain peaks have not been traversed, continue to judge whether there is a new occlusion point between two adjacent peaks and perform iteration; assign the traversed mountain peaks and the mountain peak linked list to the mountain peak diffraction path to obtain the mountain peak diffraction points;

[0056] Terrain feature calculation module: It is used to extract features of the mountain and valley terrain between the specified transmitting antenna and receiving antenna within the specified search spacing based on the digital elevation model, in combination with the terrain loading module, terrain triangular element dissection module, antenna height setting module, and two-dimensional profile calculation module.

[0057] A mountain peak diffraction point measuring device based on a digital elevation model, comprising:

[0058] Memory: It is used to store the computer program for implementing the method for measuring mountain peak diffraction points based on the digital elevation model;

[0059] A processor for implementing the method for measuring diffraction points of mountain peaks based on digital elevation model when executing the computer program.

[0060] A computer-readable storage medium,

[0061] The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it can implement the method for measuring diffraction points of mountain peaks based on digital elevation model.

[0062] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0063] 1. In a specific field undulating terrain environment, compared with traditional terrain field mapping, the present invention adopts a digital elevation model, restores and reconstructs the terrain surface by using the fewest sampling points, can improve the lack of valley and mountain peak features on the complex terrain surface, performs secondary processing on the terrain data, obtains two-dimensional profile contour data of the undulating terrain and terrain features of mountain peak vertices, and can dynamically adjust the two-dimensional profile line and the search spacing of mountain peak vertices to ensure the accuracy of measuring diffraction points of mountain peaks.

[0064] 2. Since the present invention combines a digital elevation model with a ground height picking function and a two-dimensional profile contour calculation function, uses a computer to perform refined and multi-level environmental feature extraction on the complex terrain environment, comprehensively considers various features of the terrain, effectively saves the waste of manpower and material resources brought by on-site measurement and the errors brought by manual measurement. During the feature extraction process of the real terrain environment, while ensuring accuracy, it can also save manpower and material resources to improve work efficiency, and the present invention can comprehensively apply the above functions to complete the extraction of mountain peak diffraction paths in an all-round and efficient manner.

[0065] In summary, the present invention extracts the features of valleys and mountain peaks on the real terrain environment through a digital elevation model, performs refined and multi-level environmental feature extraction on the complex terrain environment by using a ground height picking function and a two-dimensional profile contour calculation function, screens and calculates according to the extracted feature parameters, and obtains the measurement result of diffraction points of mountain peaks based on digital elevation model; therefore, it has the characteristics of comprehensive consideration factors, high accuracy rate, and strong universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 is a flowchart of the method of the present invention.

[0067] Figure 2 is a schematic diagram of terrain triangular element meshing provided by an embodiment of the present invention.

[0068] Figure 3 is a schematic diagram of an algorithm for obtaining a two-dimensional profile of a mountain body provided by an embodiment of the present invention.

[0069] Figure 4 It is a schematic diagram of a two-dimensional mountain profile provided by an embodiment of the present invention.

[0070] Figure 5 It is a schematic diagram of a mountain simulation environment provided by an embodiment of the present invention.

[0071] Figure 6 It is an effect diagram of a two-dimensional mountain profile provided by an embodiment of the present invention.

[0072] Figure 7 It is an effect diagram of a mountain peak provided by an embodiment of the present invention.

[0073] Figure 8 It is an effect diagram of the diffraction point and diffraction path of a mountain peak provided by an embodiment of the present invention. Detailed implementation manners

[0074] The present invention will be described in detail below with reference to the accompanying drawings.

[0075] Refer to Figure 1 , a method for measuring the diffraction point of a mountain peak based on a digital elevation model, comprising the following steps:

[0076] Step 1, obtain a digital elevation model, a digital three-dimensional terrain model, the three-dimensional coordinate positions of a transmitting antenna with an absolute height or a relative height, and the three-dimensional coordinate positions of a receiving antenna with an absolute height or a relative height; the absolute height is the vertical distance between the transmitting antenna or the receiving antenna and the sea level, and the relative height is the vertical distance between the transmitting antenna or the receiving antenna and the ground; the specific process is as follows: import a digital elevation model in the format of.asc and.txt suffixes, load the digital elevation model into a digital three-dimensional terrain model representing the undulating terrain simulation environment, in the same coordinate system as the digital three-dimensional terrain model, input the three-dimensional coordinate positions of the transmitting antenna and the receiving antenna, and use the ground height picking function to project the three-dimensional coordinate positions (x 1 , y 1 , z 1 ) of the transmitting antenna onto the undulating terrain to obtain the projection point (x 1 , y 1 ) of the transmitting antenna on the current terrain; project the three-dimensional coordinate positions (x 2 , y 2 , z 2 ) of the receiving antenna onto the undulating terrain to obtain the projection point (x 2 , y 2) Obtain the height of the terrain plane corresponding to the projection point based on the plane equation where the projection point is located. If the three-dimensional coordinate positions of the imported transmitting antenna and receiving antenna are absolute heights, directly proceed to step two; if the three-dimensional coordinate positions of the imported transmitting antenna and receiving antenna are relative heights, then add the relative height to the height of the terrain plane corresponding to the projection point of the three-dimensional coordinate position to obtain the absolute height of the three-dimensional coordinate position, and enter step two;

[0077] The ground height pickup function is expressed as:

[0078]

[0079]

[0080] where z 地 is the ground height obtained on the ground, and x TRI , y TRI and z TRI are the three-dimensional coordinates of the right-angled vertex of the triangular element, is the normal vector of the triangular element where it is located, and x 地 , y 地 are the coordinates of the projection point projected onto the triangular element.

[0081] The plane equation is expressed as:

[0082] A×(x TRI -x 地 )+B×(y TRI -y 地 )+C×(z TRI -z 地 ) = 0

[0083]

[0084] where is the normal vector of the triangular element where it is located, and x TRI , y TRI and z TRI are the three-dimensional coordinates of the right-angled vertex of the triangular element, and x 地 , y 地 and z 地 are the three-dimensional coordinates of any point on the triangular element except the vertex.

[0085] Step 2: Divide the digitized 3D terrain model obtained in step 1 into triangular facets according to the grid accuracy to obtain terrain triangular facet data. The specific process is: traverse the grid nodes in the digitized 3D terrain model obtained in step 1 by row, and form four 3D coordinate vertices of a grid consisting of two adjacent grid nodes in two adjacent rows of data, namely DEM[i][j], DEM[i+1][j], DEM[i][j+1] and DEM[i+1][j+1], wherein three 3D coordinate vertices can form a triangular facet, and store the triangular facets in clockwise order, namely DEM[i][j], DEM[i+1][j] and DEM[i][j+1] or DEM[i+1][j], DEM[i+1][j+1] and DEM[i][j+1], and sort all the triangular facets by row first and then by column to obtain terrain triangular facet data. The triangular facet data can be used to more accurately reflect the complexity of the terrain and improve the accuracy and precision of the model.

[0086] Step 3: Use the two-dimensional profile calculation function to calculate the terrain triangular face data obtained in step 2, the three-dimensional coordinate position of the transmitting antenna at the absolute height or relative height, and the three-dimensional coordinate position of the receiving antenna at the absolute height or relative height obtained in step 1, to obtain a two-dimensional profile data array of the undulating terrain between the transmitting antenna and the receiving antenna. The specific process is to use the two-dimensional profile calculation function to calculate the terrain triangular face data obtained in step 2, the three-dimensional coordinate position of the transmitting antenna at the absolute height or relative height, and the three-dimensional coordinate position of the receiving antenna at the absolute height or relative height obtained in step 1, to establish a unit vector, that is, starting from the transmitting antenna, traversing along the direction from the transmitting antenna to the receiving antenna at a fixed step length until the receiving antenna ends, and obtaining the height of the terrain plane where each step projection point is located in turn, and combining each step projection point and its corresponding terrain height to form a three-dimensional coordinate (x i ,y i ,z i ) and store them in sequence to obtain a two-dimensional profile data array of the undulating terrain between the transmitting antenna and the receiving antenna;

[0087] The two-dimensional profile calculation function is expressed as:

[0088] The slope formed by the projection point of the transmitting antenna and the projection point of the receiving antenna does not exist, that is, x 发射天线 =x 接收天线 ,y 发射天线 ≠y 接收天线 Situation:

[0089]

[0090] Among them, x i ,y i and zi are the three - dimensional coordinate points of the two - dimensional profile contour, i is the index number of the three - dimensional coordinate points of the two - dimensional profile contour, f(x i , y i ) is the ground height picking function, step is the fixed step size traversed along the direction from the transmitting antenna to the receiving antenna, x 发射天线 , y 发射天线 are the coordinates of the projection point of the transmitting antenna, x 接收天线 , y 接收天线 are the coordinates of the projection point of the transmitting antenna.

[0091] For the case where the slope formed by the projection points of the transmitting antenna and the receiving antenna is 0, that is, x 发射天线 ≠x 接收天线 , y 发射天线 =y 接收天线 :

[0092]

[0093] Among them, x i , y i and z i are the three - dimensional coordinate points of the two - dimensional profile contour, i is the index number of the three - dimensional coordinate points of the two - dimensional profile contour, f(x i , y i ) is the ground height picking function, step is the fixed step size traversed along the direction from the transmitting antenna to the receiving antenna, x 发射天线 , y 发射天线 are the coordinates of the projection point of the transmitting antenna, x 接收天线 , y 接收天线 are the coordinates of the projection point of the transmitting antenna.

[0094] For the case where the slope formed by the projection points of the transmitting antenna and the receiving antenna exists and is not 0, that is, x 发射天线 ≠x 接收天线 , y 发射天线 ≠y 接收天线 :

[0095]

[0096]

[0097]

[0098] Among them, x i , y i and z i are the three - dimensional coordinate points of the two - dimensional profile contour, i is the index number of the three - dimensional coordinate points of the two - dimensional profile contour, f(x i , y i) is the ground height picking function, step is the fixed step size traversed along the direction from the transmitting antenna to the receiving antenna, k is the slope formed by the projection points of the transmitting antenna and the receiving antenna, x 发射天线 and y 发射天线 are the coordinates of the projection point of the transmitting antenna, x 接收天线 and y 接收天线 are the coordinates of the projection point of the transmitting antenna.

[0099] Table 1

[0100]

[0101]

[0102]

[0103]

[0104]

[0105] Table 1 is the two-dimensional profile contour data, where x i and y i are the coordinates of the projection points of the two-dimensional profile contour data, z i is the elevation information corresponding to the projection point coordinates x i and y i of the two-dimensional profile contour. It can be seen that the two-dimensional profile contour data is an ordered three-dimensional space coordinate x i 、y i and z i composed of, so it can be concluded that the two-dimensional profile contour data is stored in the form of an array.

[0106] Step Four, compare the adjacent two-dimensional profile contour data array elements obtained in Step Three, and judge whether the current element is a peak value. If so, store the current element into the mountain peak value array; if not, the current element is a valley value element, and delete the valley value element; judge whether the distance between the two peak value array elements stored in the mountain peak value array is greater than the search spacing. If so, retain the higher mountain peak value element; if not, retain the adjacent mountain peak value array elements;

[0107] Step 5: Calculate the clearance at the obstacle point using the higher mountain peak element obtained in Step 4, the adjacent mountain peak array elements, and the three-dimensional coordinate positions of the transmitting antenna with absolute or relative height and the three-dimensional coordinate positions of the receiving antenna with absolute or relative height obtained in Step 1, and determine whether the clearance at the mountain peak obstacle point between the transmitting antenna and the receiving antenna is greater than zero. If it is, retain the current mountain peak element; if not, remove the current mountain peak element, and order and set the retained current mountain peak elements to obtain the mountain peak three-dimensional coordinate array. The formula for calculating the clearance at the obstacle point in Step 5 is as follows:

[0108]

[0109] where K is the equivalent earth radius coefficient; d T is the ground distance from the transmitting antenna to the knife-edge obstacle mountain peak, in km; d R is the ground distance from the receiving antenna to the knife-edge obstacle mountain peak, in km; d is the ground distance from the transmitting antenna to the receiving antenna, in km; h T is the altitude of the transmitting antenna, in m; h R is the altitude of the receiving antenna, in m; h is the altitude of the knife-edge obstacle mountain peak, in m.

[0110] Step 6: Based on the mountain peak three-dimensional coordinate array obtained in Step 5, sequentially determine whether there is a new occlusion point between two adjacent mountains. If so, go to Step 7; if not, continue to judge until all mountains are traversed, and obtain the mountain peak linked list by looping through the mountain peak three-dimensional coordinate array in the forward direction;

[0111] Table 2

[0112]

[0113] Table 2 shows the mountain peak point data, where x i and y i are the projected point coordinates of the mountain peak point data, and z i is the elevation information of the projected point coordinates corresponding to x i and y i of the mountain peak point. It can be seen that the mountain peak point data is obtained from the two-dimensional profile contour data in Table 1 and is also composed of the ordered spatial three-dimensional coordinates x i 、y i and z i . And to represent the front and back link relationship between the mountains, the mountain peak point data is stored in the form of a linked list.

[0114] Step 7: Based on the adjacent mountains with occlusion points obtained in Step 6, obtain the occlusion points existing between two adjacent peaks, that is, the mountain diffraction nodes, and insert the mountain diffraction nodes into the nodes of the mountain peak linked list to obtain the mountain peak linked list;

[0115] Step 8: Assign the mountain peak linked lists obtained in Step 6 and Step 7 to the mountain peak diffraction path to obtain the mountain peak diffraction points.

[0116] Table 3

[0117]

[0118] Table 3 is the diffraction point data, that is, the mountain peak diffraction path, where x i and y i are the projected point coordinates of the diffraction point data, and z i is the elevation information of the projected point coordinates x i and y i corresponding to the diffraction point. It can be seen that when there is no occlusion between adjacent mountain peak points, the diffraction point data is obtained from the mountain peak point data in Table 2 and is also composed of the ordered three-dimensional space coordinates x i 、y i and z i and is stored in the form of a linked list to represent the front and back link relationship between diffraction points.

[0119] A mountain peak diffraction point measurement system based on a digital elevation model, comprising:

[0120] A terrain loading module: used to load the digital elevation model into a digital three-dimensional terrain model representing a undulating terrain simulation environment;

[0121] A terrain triangular facet meshing module: used to mesh the digital three-dimensional terrain model according to the grid accuracy to obtain terrain triangular facet data;

[0122] An antenna height setting module: used to obtain the three-dimensional coordinate positions of the transmitting antenna with absolute height or relative height and the three-dimensional coordinate positions of the receiving antenna with absolute height or relative height;

[0123] A two-dimensional profile calculation module: used to use a two-dimensional profile calculation function according to the terrain triangular facet data, the three-dimensional coordinate positions of the transmitting antenna with absolute height or relative height, and the three-dimensional coordinate positions of the receiving antenna with absolute height or relative height to obtain an array of two-dimensional profile data of the undulating terrain between the transmitting antenna and the receiving antenna;

[0124] A mountain peak element acquisition and screening module: used to compare adjacent two-dimensional profile array elements, determine whether the current element is a peak value. If so, store the current element in the mountain peak value array; if not, the current element is a valley value element, and delete the valley value element; determine whether the distance between two peak value array elements stored in the mountain peak value array is greater than the search spacing. If so, retain the higher mountain peak value element; if not, retain the adjacent mountain peak value array elements;

[0125] Diffraction point screening module: It is used to calculate the obstacle point clearance by using the obstacle point clearance calculation formula for the obtained higher mountain peak elements, adjacent mountain peak array elements, three-dimensional coordinate positions of the transmitting antenna with absolute height or relative height, and three-dimensional coordinate positions of the receiving antenna with absolute height or relative height, and determine whether the mountain peak obstacle clearance between the transmitting antenna and the receiving antenna is greater than zero. If so, the current mountain peak element is retained; if not, the current mountain peak element is removed, and the retained current mountain peak elements are sequentially set to obtain a mountain peak three-dimensional coordinate array.

[0126] Terrain occlusion judgment module: It is used to judge whether there is a new occlusion point between two adjacent peaks. If there is an occlusion point, the occlusion point, that is, the mountain peak diffraction node, is obtained and the mountain peak diffraction node is stored in the mountain peak linked list to obtain a new mountain peak linked list; if there is no occlusion point, it is judged whether the mountain peaks have been traversed. If the mountain peaks have been traversed, the mountain peak diffraction path is output; if the mountain peaks have not been traversed, it is continued to judge whether there is a new occlusion point between two adjacent peaks and perform iteration; according to the obtained traversed mountain peaks and mountain peak linked list, they are assigned to the mountain peak diffraction path to obtain the mountain peak diffraction point.

[0127] Terrain feature calculation module: It is used to extract features of the mountain peaks and valleys between the specified search spacing and the specified transmitting antenna and receiving antenna based on the digital elevation model, in combination with the terrain loading module, terrain triangular element meshing module, antenna height setting module, and two-dimensional profile contour calculation module.

[0128] A mountain peak diffraction point measuring device based on a digital elevation model, comprising:

[0129] Memory: It is used to store a computer program for implementing the mountain peak diffraction point measuring method based on the digital elevation model described above.

[0130] Processor, which is used to implement the mountain peak diffraction point measuring method based on the digital elevation model when executing the computer program.

[0131] A computer-readable storage medium,

[0132] The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it can implement a mountain peak diffraction point measuring method based on a digital elevation model.

[0133] See Figure 2, which is a schematic diagram of the terrain triangular element meshing in the embodiments of the present invention. The x and y axes are plane coordinates, and the z axis is the corresponding elevation, with the unit being m. Based on the digital elevation model data, the present invention conducts regular triangular network modeling on the terrain. The regular triangular network of the terrain is formed by regularly arranging triangles with similar sizes and shapes to cover the entire terrain. The vertices of the triangles are arranged at equal intervals and connected by straight lines. Each triangle forms an inclined plane. The information of the three vertices of the triangular surface includes the position information of the triangular surface in the original digital elevation model. The triangular surfaces converted from the digital elevation model data will be arranged in the order from west to east and from south to north. The triangle formed by the three points determining the smallest unit of the plane, and each triangular element will be used as the smallest processing unit of the fitting surface interpolation function operation and the processing unit of the ray tracing algorithm to determine the propagation form of the ray. It can be seen that after the terrain is processed into triangular element voxels, the terrain data can be stored orderly, and the calculation efficiency can be improved while ensuring the calculation accuracy.

[0134] Figure 3 This is a schematic diagram of the calculation method for the two-dimensional section of the mountain between the transmitting antenna and the receiving antenna provided in the embodiments of the present invention. The horizontal and vertical coordinates are the coordinates of the corresponding two-dimensional projection points. Tx is the transmitting antenna, and Rx is the receiving antenna. According to the specified step length Step along the vector directions of the transmitting and receiving antennas established in Step 3, equal-step interval interpolation is performed in sequence, and the elevation information z corresponding to the two-dimensional projection point (x i , y i ) can be obtained. i , and the array (x i , y i , z i ) formed by the two-dimensional projection point and the elevation information is the two-dimensional section data of the mountain between the transmitting antenna and the receiving antenna.

[0135] Figure 4 This is a schematic diagram of the two-dimensional section of the mountain provided in the embodiments of the present invention. The x and y axes are plane coordinates, and the z axis is the corresponding elevation. Tx is the transmitting antenna, and Rx is the receiving antenna. According to the specified step length Step along the vector directions of the transmitting and receiving antennas established in Step 3, the vector is decomposed into vectors in the x and y directions, and Δx and Δy steps are taken in the x and y directions respectively, and the coordinate information (x i + Δx, y i + Δy) of the next projection point and the corresponding elevation information H i+1 can be obtained. The array (x i , y i , z i ) formed by the two-dimensional projection point and the elevation information is the two-dimensional section of the mountain between the transmitting antenna and the receiving antenna; where h p is the clearance of the obstacle point between the receiving and transmitting antennas, that is, the height of the peak of the knife-edge mountain from the line connecting the transmitting antenna and the receiving antenna.

[0136] Figure 5 This is a schematic diagram of the simulation environment provided by the embodiments of the present invention. The x and y axes are plane coordinates, and the z axis is the corresponding elevation, with the unit of all being m. It can be seen from Figure 5 that the dashed line conforming to the terrain is the two-dimensional section of the mountain between the transmitting antenna and the receiving antenna. The triangle "▲" is the peak point obtained between the sections, the asterisk "*" is the diffraction point meeting the diffraction conditions, and the straight line is the diffraction path of the radio wave propagation. The obtained radio wave propagation path based on the above can provide path support for the electromagnetic prediction of the deterministic radio wave propagation model based on the ray tracing algorithm.

[0137] Figure 6 This is the effect diagram of the two-dimensional section of the mountain provided by the embodiments of the present invention. The abscissa x is the distance between the two-dimensional projection points of the connection line between the transmitting antenna and the receiving antenna, and the ordinate y is the corresponding elevation information. Figure 6 is Figure 5 the effect diagram of the two-dimensional section under the terrain.

[0138] Figure 7 This is the effect diagram of the peak point provided by the embodiments of the present invention. The abscissa x is the distance between the two-dimensional projection points of the connection line between the transmitting antenna and the receiving antenna, and the ordinate y is the corresponding elevation information. Figure 7 is Figure 5 the effect diagram of the peak point under the terrain. It can be intuitively seen that the position of the peak point can be accurately obtained through the present invention.

[0139] Figure 8 This is the effect diagram of the diffraction point and the diffraction path provided by the embodiments of the present invention. The abscissa x is the distance between the two-dimensional projection points of the connection line between the transmitting antenna and the receiving antenna, and the ordinate y is the corresponding elevation information. Figure 8 is Figure 5 the two-dimensional effect diagram of the diffraction point and the diffraction path under the terrain. It can be directly seen that the accuracy of the diffraction point and the diffraction path obtained by the present invention is high.

Claims

1. A method for measuring diffraction points of mountain peaks based on digital elevation models, characterized in that, it includes the following steps: Step 1, obtain a digital elevation model, a digital three-dimensional terrain model, the three-dimensional coordinate positions of the transmitting antenna with absolute height or relative height, and the three-dimensional coordinate positions of the receiving antenna with absolute height or relative height; Step 2, perform triangular surface element meshing on the digital three-dimensional terrain model obtained in Step 1 according to the grid accuracy to obtain terrain triangular surface element data; Step 3, calculate the terrain triangular surface element data obtained in Step 2, the three-dimensional coordinate positions of the transmitting antenna with absolute height or relative height obtained in Step 1, and the three-dimensional coordinate positions of the receiving antenna with absolute height or relative height using a two-dimensional profile calculation function to obtain a two-dimensional profile data array of the undulating terrain between the transmitting antenna and the receiving antenna; Step 4, for the two-dimensional profile data array of the undulating terrain obtained in Step 3, compare adjacent two-dimensional profile array elements, and filter to obtain higher mountain peak elements and adjacent mountain peak array elements; Step 5, perform calculations, filtering, and aggregation on the higher mountain peak elements obtained in Step 4, the adjacent mountain peak array elements, the three-dimensional coordinate positions of the transmitting antenna with absolute height or relative height obtained in Step 1, and the three-dimensional coordinate positions of the receiving antenna with absolute height or relative height in sequence to obtain a mountain peak three-dimensional coordinate array; Step 6, based on the mountain peak three-dimensional coordinate array obtained in Step 5, sequentially determine whether there are new occlusion points between adjacent two mountain peaks. If so, enter Step 7; if not, continue to judge until all mountain peaks are traversed, and obtain a mountain peak linked list by forwardly cycling through the mountain peak three-dimensional coordinate array; Step 7, based on the adjacent mountain peaks with occlusion points obtained in Step 6, obtain the occlusion points existing between adjacent two peaks, that is, mountain peak diffraction nodes, and insert the mountain peak diffraction nodes into the nodes of the mountain peak linked list to obtain a mountain peak linked list; Step 8, assign the mountain peak linked lists obtained in Step 6 and Step 7 to the mountain peak diffraction path to obtain mountain peak diffraction points.

2. The method for measuring diffraction points of mountain peaks based on digital elevation models according to claim 1, characterized in that, The specific process of the first step is as follows: import digital elevation models with the suffixes of.asc and.txt, load the digital elevation models into digital 3D terrain models representing undulating terrain simulation environments. In the same coordinate system as the digital 3D terrain models, input the three-dimensional coordinate positions of the transmitting antenna and the receiving antenna. Use the ground height picking function to project the three-dimensional coordinate position (x 1 , y 1 , z 1 ) of the transmitting antenna onto the undulating terrain to obtain the projection point (x 1 , y 1 ) of the transmitting antenna on the current terrain; project the three-dimensional coordinate position (x 2 , y 2 , z 2 ) of the receiving antenna onto the undulating terrain to obtain the projection point (x 2 , y 2 ) of the receiving antenna on the current terrain. According to the plane equation where the projection points (x 1 , y 1 ) and (x 2 , y 2 ) are located, obtain the height of the terrain plane where the three-dimensional coordinate positions correspond to the projection points. If the three-dimensional coordinate positions of the imported transmitting antenna and receiving antenna are absolute heights, directly enter the second step; if the three-dimensional coordinate positions of the imported transmitting antenna and receiving antenna are relative heights, add the relative height to the height of the plane where the three-dimensional coordinate positions correspond to the projection points to obtain the absolute height of the three-dimensional coordinate positions, and then enter the second step; the ground height picking function is expressed as: where z 地 is the ground height obtained on the ground, x TRI , y TRI and z TRI are the three-dimensional coordinates of the right-angled vertex of the triangular surface element, is the normal vector of the triangular surface element where it is located, x 地 , y 地 are the coordinates of the projection point projected onto the triangular surface element; the plane equation is expressed as: A×(x TRI -x 地 )+B×(y TRI -y 地 )+C×(z TRI -z 地 ) = 0 Among them, is the normal vector of the triangle element surface, and x TRI , y TRI and z TRI are the three-dimensional coordinates of the right-angled vertex of the triangle element surface, and x 地 , y 地 and z 地 are the three-dimensional coordinates of any point on the triangle element surface other than the vertex.

3. The method for measuring diffraction points of mountain peaks based on digital elevation models according to claim 1, characterized in that, The specific process of the second step is to traverse the grid nodes in the digital three-dimensional terrain model obtained in the first step row by row. Two adjacent grid nodes in two adjacent rows of data form the four three-dimensional coordinate vertices of a grid, namely DEM[i][j], DEM[i + 1][j], DEM[i][j + 1], and DEM[i + 1][j + 1]. Among them, three three-dimensional coordinate vertices can form a triangular patch. The triangular patch is stored in clockwise order, that is: DEM[i][j], DEM[i + 1][j], and DEM[i][j + 1] or DEM[i + 1][j], DEM[i + 1][j + 1], and DEM[i][j + 1]. All triangular patches are sorted first by row and then by column to obtain the terrain triangular patch data.

4. A method for measuring diffraction points of a mountain peak based on a digital elevation model according to claim 1, characterized in that, The specific process of the third step is as follows: using the two-dimensional profile calculation function, establish a unit vector with the terrain triangle element data obtained in the second step, the three-dimensional coordinate positions of the transmitting antenna with absolute height or relative height obtained in the first step, and the three-dimensional coordinate positions of the receiving antenna with absolute height or relative height. That is, starting from the transmitting antenna, traverse to the receiving antenna at a fixed step length along the direction from the transmitting antenna to the receiving antenna, and sequentially obtain the height of the terrain plane where each step projection point is located. Combine each step projection point and its corresponding terrain height to form three-dimensional coordinates (x i , y i , z i ) and store them in order to obtain the two-dimensional profile data array of the undulating terrain between the transmitting antenna and the receiving antenna.

5. A method for measuring diffraction points of a mountain peak based on a digital elevation model according to claim 4, characterized in that, The two-dimensional profile calculation function is expressed as: For the case where the slope formed by the projection points of the transmitting antenna and the receiving antenna does not exist, i.e., x 发射天线 = x 接收天线 , y 发射天线 ≠ y 接收天线 : where x i , y i and z i are the three-dimensional coordinate points of the two-dimensional profile, i is the index number of the three-dimensional coordinate points of the two-dimensional profile, f(x i , y i ) is the ground height picking function, step is the fixed step size traversed along the direction from the transmitting antenna to the receiving antenna, x 发射天线 , y 发射天线 are the coordinates of the projection point of the transmitting antenna, x 接收天线 , y 接收天线 are the coordinates of the projection point of the transmitting antenna; For the case where the slope formed by the projection points of the transmitting antenna and the receiving antenna is 0, that is, x 发射天线 ≠x 接收天线 , y 发射天线 =y 接收天线 : Among them, x i , y i and z i are the three-dimensional coordinate points of the two-dimensional profile, i is the index number of the three-dimensional coordinate points of the two-dimensional profile, f(x i , y i ) is the ground height picking function, step is the fixed step size traversed along the direction from the transmitting antenna to the receiving antenna, x 发射天线 , y 发射天线 are the coordinates of the projection point of the transmitting antenna, x 接收天线 , y 接收天线 are the coordinates of the projection point of the transmitting antenna; For the case where the slope formed by the projection points of the transmitting antenna and the receiving antenna exists and is not 0, i.e., x 发射天线 ≠ x 接收天线 , y 发射天线 ≠ y 接收天线 : Among them, x i , y i and z i are the three-dimensional coordinate points of the two-dimensional profile, i is the index number of the three-dimensional coordinate points of the two-dimensional profile, f(x i , y i ) is the ground height picking function, step is the fixed step size traversed along the direction from the transmitting antenna to the receiving antenna, k is the slope formed by the projection points of the transmitting antenna and the receiving antenna, x 发射天线 , y 发射天线 are the coordinate points of the projection point of the transmitting antenna, x 接收天线 , y 接收天线 are the coordinate points of the projection point of the transmitting antenna.

6. A method for measuring diffraction points of a mountain peak based on a digital elevation model according to claim 1, characterized in that, The specific process of the fourth step is as follows: According to the undulating terrain two-dimensional profile data array obtained in the third step, compare adjacent two-dimensional profile array elements, and judge whether the current element is a peak value. If so, store the current element in the mountain peak value array; if not, the current element is a valley value element, and delete the valley value element; judge whether the distance between two peak value array elements stored in the mountain peak value array is greater than the search spacing. If so, retain the higher mountain peak value element; if not, retain adjacent mountain peak value array elements.

7. A method for measuring diffraction points of a mountain peak based on a digital elevation model according to claim 1, characterized in that, The specific process of the fifth step is as follows: Use the higher mountain peak value elements and adjacent mountain peak value array elements obtained in the fourth step, the three-dimensional coordinate position of the transmitting antenna with absolute height or relative height and the three-dimensional coordinate position of the receiving antenna with absolute height or relative height obtained in the first step, and calculate using the obstacle point clearance calculation formula to obtain the obstacle point clearance. Judge whether the mountain peak obstacle point clearance between the transmitting antenna and the receiving antenna is greater than zero. If so, retain the current mountain peak value element; if not, remove the current mountain peak value element, and collect the retained current mountain peak value elements in order to obtain the mountain peak three-dimensional coordinate array; The calculation formula for the obstacle point clearance is: where K is the equivalent earth radius coefficient; d T is the ground distance from the transmitting antenna to the knife-edge obstacle peak, in km; d R is the ground distance from the receiving antenna to the knife-edge obstacle peak, in km; d is the ground distance from the transmitting antenna to the receiving antenna, in km; h T is the altitude of the transmitting antenna, in m; h R is the altitude of the receiving antenna, in m; h is the altitude of the knife-edge obstacle peak, in m.

8. A system for measuring diffraction points of a mountain peak based on a digital elevation model, characterized in that, comprising: A terrain loading module: used to load the digital elevation model to represent a digital three-dimensional terrain model of an undulating terrain simulation environment; A terrain triangular patch meshing module: used to mesh the digital three-dimensional terrain model according to the grid accuracy to obtain terrain triangular patch data; An antenna height setting module: used to obtain the three-dimensional coordinate position of the transmitting antenna with absolute height or relative height and the three-dimensional coordinate position of the receiving antenna with absolute height or relative height; Two-dimensional profile calculation module: It is used to obtain the two-dimensional profile data array of the undulating terrain between the transmitting antenna and the receiving antenna by using the two-dimensional profile calculation function according to the terrain triangular element data, the three-dimensional coordinate position of the transmitting antenna with absolute height or relative height, and the three-dimensional coordinate position of the receiving antenna with absolute height or relative height; Mountain peak element acquisition and screening module: It is used to compare two adjacent two-dimensional profile array elements, determine whether the current element is a peak value. If so, store the current element into the mountain peak value array; if not, the current element is a valley value element, and delete the valley value element; judge whether the distance between two peak value array elements stored in the mountain peak value array is greater than the search spacing. If so, retain the higher mountain peak element; if not, retain the adjacent mountain peak value array elements; Diffraction point screening module: It is used to calculate the obstacle point clearance by using the obstacle point clearance calculation formula with the obtained higher mountain peak elements, adjacent mountain peak value array elements, the three-dimensional coordinate position of the transmitting antenna with absolute height or relative height, and the three-dimensional coordinate position of the receiving antenna with absolute height or relative height, and judge whether the mountain peak obstacle point clearance between the transmitting antenna and the receiving antenna is greater than zero. If so, retain the current mountain peak element; if not, remove the current mountain peak element, and set the order of the retained current mountain peak elements to obtain the mountain peak three-dimensional coordinate array; Terrain occlusion judgment module: It is used to judge whether there is a new occlusion point between two adjacent peaks. If there is an occlusion point, obtain the occlusion point, that is, the mountain peak diffraction node, and store the mountain peak diffraction node into the mountain peak linked list to obtain a new mountain peak linked list; If there is no occlusion point, judge whether the mountains have been traversed. If the mountains have been traversed, output the mountain peak diffraction path; If the mountains have not been traversed, continue to judge whether there is a new occlusion point between two adjacent peaks and perform iteration; assign the traversed mountains and the mountain peak linked list to the mountain peak diffraction path to obtain the mountain peak diffraction point; Terrain feature calculation module: It is used to extract features of the mountain and valley terrain within the specified search spacing and between the specified transmitting antenna and receiving antenna based on the digital elevation model, in combination with the terrain loading module, terrain triangular element dissection module, antenna height setting module, and two-dimensional profile calculation module.

9. A mountain peak diffraction point measuring device based on a digital elevation model, characterized in that, it includes: A memory: It is used to store a computer program for implementing a mountain peak diffraction point measuring method based on a digital elevation model as claimed in claims 1-7; A processor, which is used to implement the mountain peak diffraction point measuring method based on a digital elevation model as claimed in claims 1-7 when executing the computer program.

10. A computer-readable storage medium, characterized in that, the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it can implement the mountain peak diffraction point measuring method based on a digital elevation model as claimed in claims 1-7.

Images