Intervisibility calculation method, device and equipment based on digital elevation model and medium

Abstract

The embodiment of the invention provides an intervisibility calculation method, device, equipment and medium based on a digital elevation model.The method comprises the steps that geographic coordinates of an observation point and a target point are obtained, the geographic coordinates are converted into observation grid points and target grid points based on the digital elevation model, and elevation values of the observation grid points are obtained; according to the coordinate values of the observation grid points and the elevation values of the observation grid points, calculating to obtain the lowest visual height value of each grid point of the digital elevation model, and taking a set of the lowest visual height values corresponding to all the grid points as lowest visual height data; and according to the coordinate value of the target grid point, obtaining a minimum visual height value corresponding to the target grid point from the minimum visual height data, judging whether the elevation value of the observation grid point is greater than or equal to the minimum visual height value of the target grid point, and if so, determining that the target point and the observation point are visual. According to the scheme, through the elevation information of the digital elevation model, the speed and efficiency of intervisibility calculation are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of line of sight analysis, and in particular to a line of sight calculation method, device, equipment and medium based on a digital elevation model. Background Art

[0002] Line of sight analysis refers to terrain analysis that uses a certain point as an observation point to study the line of sight of a certain area. It is a technical method that uses digital elevation models to determine whether any two points on the terrain can be seen from each other.

[0003] The essence of line-of-sight analysis belongs to the category of optimizing terrain, such as setting up radar stations, TV stations, and marine navigation. In the military, it includes setting up positions, observation posts, and real-time simulation systems. The establishment of digital elevation models provides a favorable basis for this type of analysis, and can easily calculate the various parts that can be seen from an observation point. In the digital elevation model, the location of the observation point is identified, a family of rays are drawn from this location, and the elevation of each point (pixel in the elevation matrix) through which the ray passes is compared, and then the target point can be analyzed and calculated to be visible.

[0004] Although the concept of line of sight analysis is simple, it is very important for certain types of simulations, such as computer-generated force (CGF) systems and sensor simulations. In CGF simulation systems, a large number of intervisibility judgments are required, and each intervisibility judgment may take a lot of computing time. Therefore, traditional intervisibility judgments are often the most time-consuming operations, occupying a large amount of system computing resources and affecting the real-time performance of the system. How to improve the computational efficiency of intervisibility analysis and avoid the excessive judgment and calculation time caused by the large amount of raster data in the digital elevation model, so as to improve the efficiency of real-time computing and analysis, is a key issue that needs to be solved. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides a method for calculating line of sight based on a digital elevation model to solve the technical problems of low accuracy and low calculation efficiency of line of sight analysis in the prior art. The method includes: Obtaining geographic coordinates of an observation point and a target point, converting the geographic coordinates into observation grid points and target grid points based on a digital elevation model, and obtaining elevation values ​​of the observation grid points; According to the coordinate values ​​of the observation grid points and the elevation values ​​of the observation grid points, the lowest visible height value of each grid point of the digital elevation model is calculated, and the set of the lowest visible height values ​​corresponding to all the grid points is used as the lowest visible height data; According to the coordinate value of the target grid point, the minimum visible height value corresponding to the target grid point is obtained from the minimum visible height data, and it is determined whether the elevation value of the observation grid point is greater than or equal to the minimum visible height value of the target grid point. If so, the target point and the observation point are visible, and if not, the target point and the observation point are not visible.

[0006] The embodiment of the present invention also provides a visual line calculation device based on a digital elevation model to solve the technical problems of low accuracy and low calculation efficiency of visual line analysis in the prior art. The device includes: A coordinate conversion module is used to obtain the geographic coordinates of the observation point and the target point, convert the geographic coordinates into the observation grid point and the target grid point based on the digital elevation model, and obtain the elevation value of the observation grid point; A pre-calculation module, used to calculate the minimum visible height value of each grid point of the digital elevation model according to the coordinate value of the observation grid point and the elevation value of the observation grid point, and take the set of the minimum visible height values ​​corresponding to all the grid points as the minimum visible height data; A visibility judgment module is used to obtain the minimum visible height value corresponding to the target grid point from the minimum visible height data according to the coordinate value of the target grid point, and judge whether the elevation value of the observation grid point is greater than or equal to the minimum visible height value of the target grid point. If so, the target point and the observation point are visible, and if not, the target point and the observation point are not visible.

[0007] An embodiment of the present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the processor implements any of the above-mentioned methods for calculating visibility based on a digital elevation model to solve the technical problems of low accuracy and low calculation efficiency of visibility analysis in the prior art.

[0008] An embodiment of the present invention further provides a computer-readable storage medium storing a computer program for executing any of the above-mentioned digital elevation model-based visibility calculation methods to solve the technical problems of low accuracy and low calculation efficiency of visibility analysis in the prior art.

[0009] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects: The visibility calculation method of the embodiment of the present invention pre-calculates the minimum visible height data and uses the data to perform real-time visibility analysis, thereby avoiding the problem of requiring a large amount of calculation each time a visibility judgment is made, thereby greatly improving the speed and efficiency of the visibility calculation and effectively improving the real-time performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 It is a flow chart of a method for calculating visibility based on a digital elevation model provided by an embodiment of the present invention; Figure 2 is a structural block diagram of a computer device provided by an embodiment of the present invention; Figure 3 It is a structural block diagram of a visual line of sight calculation device based on a digital elevation model provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0012] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0013] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0014] In an embodiment of the present invention, a method for calculating visibility based on a digital elevation model is provided. Figure 1 As shown, the method includes: Step S101: obtaining geographic coordinates of an observation point and a target point, converting the geographic coordinates into observation grid points and target grid points based on a digital elevation model, and obtaining elevation values ​​of the observation grid points; Step S102: Calculate the minimum visible height value of each grid point of the digital elevation model according to the coordinate value of the observation grid point and the elevation value of the observation grid point (the minimum visible height value is the minimum height value required for the grid point to be visible to the target grid point), and take the set of the minimum visible height values ​​corresponding to all the grid points as the minimum visible height data; Step S103: According to the coordinate value of the target grid point, the minimum visible height value corresponding to the target grid point is obtained from the minimum visible height data, and it is determined whether the elevation value of the observation grid point is greater than or equal to the minimum visible height value of the target grid point. If so, the target point is visible to the observation point, and if not, the target point is not visible to the observation point.

[0015] In specific implementation, the following steps are performed to calculate the lowest visible height value of each grid point of the digital elevation model according to the coordinate value of the observation grid point and the elevation value of the observation grid point: Construct a ray parameter equation, discretize the ray parameter equation to generate a ray path from the observation grid point to the target grid point, determine the sampling interval of the ray on the ray path according to the required accuracy, obtain the coordinate value of the intermediate grid point on the ray path according to the sampling interval; traverse each of the intermediate grid points along the ray path until all the intermediate grid points are processed: Obtain the elevation value of the intermediate grid point; if the elevation value of the intermediate grid point is greater than the elevation value of the observation grid point, use the elevation value of the intermediate grid point as the minimum visible height value; if the elevation value of the intermediate grid point is less than or equal to the elevation value of the observation grid point, use the elevation value of the observation grid point as the minimum visible height value.

[0016] Specifically, point-by-point ray traversal draws a ray from the observation point (i.e., observation point) to each target point, and checks whether the elevation of all intermediate points on the ray path (i.e., sampling points between the observation point and the target point on the ray path) blocks the line of sight. If the elevation of all intermediate points does not exceed the line of sight, the target point is visible. Accuracy is ensured by checking point by point, which is suitable for scenes with high precision requirements, but the computational complexity is O(n 2 ), suitable for small and medium-sized digital elevation model-based data. Once an intermediate point is found to be blocked, subsequent checks are stopped immediately. Manhattan distance or step count can also be used instead of Euclidean distance to speed up the calculation (with a trade-off in accuracy). Each target point is processed independently, suitable for parallelization to improve efficiency.

[0017] In specific implementation, the following steps are performed to calculate the lowest visible height value of each grid point of the digital elevation model according to the coordinate value of the observation grid point and the elevation value of the observation grid point: According to the coordinate values ​​of the observation grid points, all the grid points are divided into different radial sections with the observation grid point as the center, each of the grid points belongs to at least one radial section, and the grid points in each radial section are sorted to generate a sorted radial section group; the invisible grid points in each radial section are marked, and the invisible grid points are deleted from the sorted radial section group; for each radial section in the sorted radial section group, the grid points are sorted in descending order according to the distance between the grid point and the observation grid point. In increasing order, the global maximum elevation slope relative to the observation grid point is calculated, and the minimum visible height value of each grid point is calculated according to the global maximum elevation slope and the elevation value of the observation grid point; taking each grid point as a unit, all the radial sections are traversed to obtain the minimum visible height value of each grid point in each radial section, and at least one minimum visible height value corresponding to each grid point is obtained, and the maximum value of the at least one minimum visible height value is used as the minimum visible height value of each grid point.

[0018] In specific implementation, the following steps are performed to divide all the grid points into different radial sections, and after sorting the grid points in each radial section, a sorted radial section group is generated: The digital elevation model is divided into a plurality of radial sections with the observation grid point as the center and the set angle step as the interval; all grid points in the digital elevation model are traversed, the level angle of each grid point is calculated by the coordinate value of each grid point, and the level angle is mapped to 0 to 360 degrees to generate a mapped level angle; each grid point is assigned to the radial section closest to the grid point according to the mapped level angle and the angle step to generate a radial section group; in the radial section group, the grid points are sorted from near to far according to the distance from the observation grid point to generate a sorted radial section group.

[0019] In specific implementation, the following steps are performed to calculate the global maximum elevation slope relative to the observation grid point, and the minimum visible height value of each grid point is calculated based on the global maximum elevation slope and the elevation value of the observation grid point: Calculate the total distance between each of the grid points and the observation grid point; obtain the intermediate grid point between the lines connecting the grid point and the observation grid point, and calculate the distance between each of the intermediate grid points and the observation grid point; calculate the elevation slope of the intermediate grid point relative to the observation grid point based on the distance, the elevation value of the observation point and the elevation value of each of the grid points; compare the elevation slopes of all the intermediate grid points, and take the maximum elevation slope as the global maximum elevation slope; calculate the minimum visible height of each of the grid points through the total distance, the global maximum elevation slope and the elevation value of the observation grid point.

[0020] Specifically, we traverse the ray point by point (with a complexity of O(n 2 )) is converted to radial profile scanning, using maximum elevation angle tracking and spatial coherence to reduce the complexity to O( ) (m is the radial number, usually much smaller than n 2 ). The key is to avoid repeated traversal of intermediate points by precalculating the minimum visible height of each target point.

[0021] In one embodiment, first, the polar coordinates are divided and radial profiles are scanned, and the digital elevation model is divided into radial profiles of multiple angles around the observation point (e.g., one profile per degree, 360 in total, the smaller the radial interval, the higher the accuracy, but the amount of calculation increases. Usually 1°~5° is taken to balance efficiency and accuracy); in each profile, the grid points are sorted from near to far according to the distance from the observation point.

[0022] Secondly, single profile processing and maximum elevation angle tracking are performed. For each radial profile, points are processed incrementally by distance, the current maximum elevation angle slope is dynamically maintained, and the minimum visible altitude of subsequent points is quickly derived.

[0023] For the grid point P in the profile (the total distance from the observation point is ), whose minimum altitude depends on the maximum elevation slope of all intermediate grid points on the path: . Where P is the grid point in the radial section, is the lowest visible height of point P, d is the distance between all the intermediate grid points on the path and the observation point, is the elevation of the observation grid point, is the elevation value of the middle grid point.

[0024] Since each grid point may belong to multiple radial sections, the The maximum value is used as the final minimum visible height value to ensure that all paths are covered.

[0025] After the minimum visible height data is generated by pre-calculation, in the process of analyzing the visibility, the real-time analysis only needs to query and compare the minimum visible height data to get the result. In actual use, if the observation point moves, the minimum visible height data needs to be re-pre-calculated and generated. The data calculation can be optimized by incrementally updating the affected sections.

[0026] The overall complexity of precalculation using the above method is , the complexity of real-time analysis is , reducing the computational complexity from O(n 2 ) down to Pre-calculation and It is suitable for real-time query of large-scale satellite terrain data (military reconnaissance simulation, base station planning, etc.).

[0027] In specific implementation, in order to introduce a heuristic algorithm, quickly exclude obviously invisible target points, and reduce the amount of precise calculation, the following steps are performed to mark the invisible grid points in each radial section: A preset maximum visible distance is set according to the curvature of the earth, atmospheric refraction, and the sensor's perception limit range. If the relative distance between the target grid point and the observation grid point is greater than the preset maximum visible distance, the current target grid point is marked as the invisible target grid point; or, if the elevation value of the target grid point is , marking the target grid point as the invisible target grid point, wherein, is the radius of the Earth, is the elevation value of the target grid point, is the elevation value of the observation grid point, is the relative distance between the target grid point and the observation grid point; or, obtain the maximum elevation point of the radial section where the target grid point is located. If the relative distance between the target grid point and the observation grid point is greater than the relative distance between the maximum elevation point and the observation grid point, and the elevation value of the target grid point is less than the elevation value of the maximum elevation point, then mark the target grid point as an invisible target grid point.

[0028] In specific implementation, in order to introduce a heuristic algorithm, quickly exclude obviously invisible target points, and reduce the amount of precise calculation, the following steps are performed to mark the invisible grid points in each radial section: The historical minimum elevation slope of each radial section is obtained according to the historical elevation data, wherein the historical elevation data is the elevation slope of the target grid point calculated during the previous visibility calculation process; if the elevation slope of the target grid point is less than the historical minimum elevation slope, the target grid point is marked as an invisible target grid point.

[0029] Specifically, the distance (due to the curvature of the earth, atmospheric refraction or sensor range, the distant points cannot be seen) is used to filter out distant points quickly. That is, if the relative distance between the grid target point and the observation point grid is greater than the preset maximum visible distance, it is directly marked as invisible.

[0030] Calculate the effect of the earth's curvature on the line of sight. If the target point elevation is , directly mark it as invisible. ,in, is the radius of the Earth, is the elevation value of the target grid point, is the elevation value of the observation grid point, is the relative distance between the target grid point and the observation grid point.

[0031] Based on the directional slope statistics, the lower limit of the elevation angle is filtered. The historical minimum elevation angle of each angle profile is pre-calculated , below which the value is blocked by the terrain (i.e. ).

[0032] In addition, based on the pre-calculated peak point, if the target point is located behind a terrain barrier in a certain direction and its elevation is lower than the barrier point (maximum elevation angle point), it will be directly invisible.

[0033] In this embodiment, a computer device is provided, such as Figure 2 As shown, it includes a memory 201, a processor 202, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, any of the above-mentioned line of sight calculation methods based on the digital elevation model is implemented.

[0034] Specifically, the computer device may be a computer terminal, a server or a similar computing device.

[0035] In this embodiment, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program for executing any of the above-mentioned digital elevation model-based visibility calculation methods.

[0036] Specifically, computer-readable storage media include permanent and non-permanent, removable and non-removable media, and information storage can be achieved by any method or technology. Information can be computer-readable instructions, data structures, modules of programs or other data. Examples of computer-readable storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, read-only compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable storage media does not include temporary computer-readable media (transitory media), such as modulated data signals and carrier waves.

[0037] Based on the same inventive concept, a line of sight calculation device based on a digital elevation model is also provided in an embodiment of the present invention, as described in the following embodiments. Since the principle of solving the problem by the line of sight calculation device based on a digital elevation model is similar to that of the line of sight calculation method based on a digital elevation model, the implementation of the line of sight calculation device based on a digital elevation model can refer to the implementation of the line of sight calculation method based on a digital elevation model, and the repeated parts will not be repeated. As used below, the term "unit" or "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived.

[0038] Figure 3 is a structural block diagram of a visual line of sight computing device based on a digital elevation model according to an embodiment of the present invention, such as Figure 3 As shown, it includes: a coordinate conversion module 301, a pre-calculation module 302 and a visibility judgment module 303, and the structure is described below.

[0039] The coordinate conversion module 301 is used to obtain the geographical coordinates of the observation point and the target point, convert the geographical coordinates into the observation grid point and the target grid point based on the digital elevation model, and obtain the elevation value of the observation grid point; The pre-calculation module 302 is used to calculate the minimum visible height value of each grid point of the digital elevation model according to the coordinate value of the observation grid point and the elevation value of the observation grid point, and take the set of the minimum visible height values ​​corresponding to all the grid points as the minimum visible height data; The visibility judgment module 303 is used to obtain the minimum visible height value corresponding to the target grid point from the minimum visible height data according to the coordinate value of the target grid point, and judge whether the elevation value of the observation grid point is greater than or equal to the minimum visible height value of the target grid point. If so, the target point and the observation point are visible, and if not, the target point and the observation point are not visible.

[0040] In one embodiment, the pre-calculation module includes: A section division unit is used to divide all the grid points into different radial sections based on the coordinate values ​​of the observation grid points and with the observation grid points as the center, each of the grid points belongs to at least one radial section, and after sorting the grid points in each radial section, a sorted radial section group is generated; an invisible grid point deleting unit, used for marking the invisible grid points in each of the radial sections, and deleting the invisible grid points from the sorted radial section group; A minimum visible height calculation unit is used to calculate, for each radial section in the sorted radial section group, a global maximum elevation slope relative to the observation grid point in the order of increasing distances between the grid point and the observation grid point, and calculate the minimum visible height value of each grid point according to the global maximum elevation slope and the elevation value of the observation grid point; The first minimum visible height set generating unit is used to traverse all the radial sections with each grid point as a unit, obtain the minimum visible height value of each grid point in each radial section, obtain at least one minimum visible height value corresponding to each grid point, and take the maximum value of at least one minimum visible height value as the minimum visible height value of each grid point.

[0041] In one embodiment, a dividing section unit is used to divide the digital elevation model into multiple radial sections with the observation grid point as the center and the set angle step as the interval; traverse all grid points in the digital elevation model, calculate the level angle of each grid point through the coordinate value of each grid point, and map the level angle to 0 to 360° to generate a mapped level angle; assign each grid point to the radial section closest to the grid point according to the mapped level angle and the angle step to generate a radial section group; in the radial section group, sort the grid points from near to far according to the distance from the observation grid point to generate a sorted radial section group.

[0042] In one embodiment, a minimum visible height value calculation unit is used to calculate the total distance between each of the grid points and the observation grid point; obtain the intermediate grid point between the line connecting the grid point and the observation grid point, and calculate the distance between the intermediate grid point and the observation grid point; calculate the elevation slope of the intermediate grid point relative to the observation grid point based on the distance, the elevation value of the observation point and the elevation value of each of the grid points; compare the elevation slopes of all the intermediate grid points, and take the maximum elevation slope as the global maximum elevation slope; calculate the minimum visible height of each of the grid points through the total distance, the global maximum elevation slope and the elevation value of the observation grid point.

[0043] In one embodiment, the invisible grid point deletion unit is used to set a preset maximum visible distance according to the curvature of the earth, atmospheric refraction and the perception limit range of the sensor. If the relative distance between the target grid point and the observation grid point is If the elevation value of the target grid point is greater than the preset maximum visible distance, the current target grid point is marked as an invisible target grid point; or , marking the target grid point as the invisible target grid point, wherein, is the radius of the Earth, is the elevation value of the target grid point, is the elevation value of the observation grid point, is the relative distance between the target grid point and the observation grid point; or, obtaining the maximum elevation point of the radial section where the target grid point is located, if the relative distance between the target grid point and the observation grid point is If the distance between the target grid point and the observation grid point is greater than the relative distance between the maximum elevation angle point and the observation grid point, and the elevation value of the target grid point is less than the elevation value of the maximum elevation angle point, the target grid point is marked as the invisible target grid point.

[0044] In one embodiment, the invisible grid point deletion unit is further used to obtain the historical minimum elevation slope of each radial section according to the historical elevation data. , wherein the historical elevation angle data is the elevation angle slope of the target grid point calculated in the previous line of sight calculation process; if the elevation angle slope of the target grid point is less than the historical minimum elevation angle slope , marking the target grid point as the invisible target grid point.

[0045] In one embodiment, the pre-calculation module includes: A path generation unit is used to construct a ray parameter equation, discretize the ray parameter equation to generate a ray path from the observation grid point to the target grid point, determine a sampling interval of the ray on the ray path according to the required accuracy, and obtain the coordinate value of the intermediate grid point on the ray path according to the sampling interval; A path traversal unit is used to traverse each of the intermediate grid points along the ray path until all the intermediate grid points are processed: An elevation acquisition unit is used to acquire the elevation value of the middle grid point from the minimum visible height data according to the coordinate value of the middle grid point; A minimum visible height calculation unit, configured to use the elevation value of the intermediate grid point as the minimum visible height value of the intermediate grid point if the elevation value of the intermediate grid point is greater than the elevation value of the observation grid point; The second minimum visible height set generating unit is used to use the elevation value of the observation grid point as the minimum visible height value of the intermediate grid point if the elevation value of the intermediate grid point is less than or equal to the elevation value of the observation grid point.

[0046] The embodiments of the present invention achieve the following technical effects: The visibility calculation method of the embodiment of the present invention pre-calculates the minimum visible height data and uses the data to perform real-time visibility analysis, thereby avoiding the problem of needing to perform a large amount of calculations each time a visibility judgment is made, thereby greatly improving the speed and efficiency of the visibility calculation and effectively improving the real-time performance of the system; the visibility calculation method of the embodiment of the present invention can effectively avoid the problem of long judgment calculation time caused by excessive amount of raster data based on the digital elevation model, thereby further improving the efficiency of real-time calculation and analysis, being simple and efficient, and not requiring complex equal-area cutting processing and equal-height processing, and being able to obtain more accurate visibility analysis results.

[0047] Obviously, those skilled in the art should understand that the modules or steps of the above-mentioned embodiments of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, and optionally, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order from that here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. In this way, the embodiments of the present invention are not limited to any specific combination of hardware and software.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the embodiments of the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calculating visibility based on a digital elevation model, characterized in that: include: Obtaining geographic coordinates of an observation point and a target point, converting the geographic coordinates into observation grid points and target grid points based on a digital elevation model, and obtaining elevation values ​​of the observation grid points; According to the coordinate values ​​of the observation grid points and the elevation values ​​of the observation grid points, the lowest visible height value of each grid point of the digital elevation model is calculated, and the set of the lowest visible height values ​​corresponding to all the grid points is used as the lowest visible height data; According to the coordinate value of the target grid point, the minimum visible height value corresponding to the target grid point is obtained from the minimum visible height data, and it is determined whether the elevation value of the observation grid point is greater than or equal to the minimum visible height value of the target grid point. If so, the target point and the observation point are visible, and if not, the target point and the observation point are not visible.

2. The method for calculating visibility based on a digital elevation model according to claim 1, wherein: Calculating the lowest visible height value of each grid point of the digital elevation model according to the coordinate value of the observation grid point and the elevation value of the observation grid point includes: According to the coordinate values ​​of the observation grid points, all the grid points are divided into different radial sections with the observation grid points as the center, each of the grid points belongs to at least one radial section, and the grid points in each radial section are sorted to generate a sorted radial section group; marking the invisible grid points in each of the radial sections, and deleting the invisible grid points from the sorted radial section group; For each of the radial sections in the sorted radial section group, in the order of increasing distances between the grid points and the observation grid points, the global maximum elevation slope relative to the observation grid points is calculated, and the minimum visible height value of each of the grid points is calculated according to the global maximum elevation slope and the elevation value of the observation grid points; Taking each grid point as a unit, traverse all the radial sections, obtain the lowest visible height value of each grid point in each radial section, obtain at least one lowest visible height value corresponding to each grid point, and take the maximum value of at least one lowest visible height value as the lowest visible height value of each grid point.

3. The method for calculating visibility based on a digital elevation model according to claim 2, wherein: Dividing all the grid points into different radial sections, sorting the grid points in each radial section, and generating a sorted radial section group, including: Taking the observation grid point as the center and the set angle step as the interval, the digital elevation model is divided into a plurality of radial sections; Traversing all grid points in the digital elevation model, calculating the level angle of each grid point according to the coordinate value of each grid point, and mapping the level angle to 0 to 360 degrees to generate a mapped level angle; Allocating each of the grid points to the radial section closest to the grid point according to the mapped rear-stage angle and the angle step, to generate a radial section group; In the radial section group, the grid points are sorted from near to far according to the distance from the observation grid point to generate a sorted radial section group.

4. The method for calculating visibility based on a digital elevation model according to claim 2, wherein: Calculating the global maximum elevation angle slope relative to the observation grid point, and calculating the minimum visible height value of each grid point according to the global maximum elevation angle slope and the elevation value of the observation grid point, including: Calculating the total distance between each of the grid points and the observation grid point; Obtaining the intermediate grid points between the lines connecting the grid points and the observation grid points, and calculating the distance between each of the intermediate grid points and the observation grid points; Calculate the elevation slope of the intermediate grid point relative to the observation grid point according to the distance, the elevation value of the observation point and the elevation value of each grid point; Comparing the elevation slopes of all the intermediate grid points, and taking the maximum elevation slope as the global maximum elevation slope; The lowest visible height of each grid point is calculated through the total distance, the global maximum elevation slope, and the elevation value of the observation grid point.

5. The method for calculating visibility based on a digital elevation model according to claim 2, wherein: Marking the grid points that are not visible in each of the radial sections, comprising: A preset maximum visible distance is set according to the curvature of the earth, atmospheric refraction and the perception limit range of the sensor, and if the relative distance between the target grid point and the observation grid point is greater than the preset maximum visible distance, the current target grid point is marked as the invisible target grid point; or, If the elevation value of the target grid point , marking the target grid point as the invisible target grid point, wherein, is the radius of the Earth, is the elevation value of the target grid point, is the elevation value of the observation grid point, is the relative distance between the target grid point and the observation grid point; or, Obtain the maximum elevation point of the radial section where the target grid point is located. If the relative distance between the target grid point and the observation grid point is greater than the relative distance between the maximum elevation point and the observation grid point, and the elevation value of the target grid point is less than the elevation value of the maximum elevation point, mark the target grid point as the invisible target grid point.

6. The method for calculating visibility based on a digital elevation model according to claim 2, wherein: Marking the grid points that are not visible in each of the radial sections, comprising: Acquire the historical minimum elevation slope of each radial section according to the historical elevation data, wherein the historical elevation data is the elevation slope of the target grid point calculated in the previous line of sight calculation process; If the elevation slope of the target grid point is less than the historical minimum elevation slope, the target grid point is marked as an invisible target grid point.

7. The method for calculating visibility based on a digital elevation model according to any one of claims 1 to 6, characterized in that: Calculating the lowest visible height value of each grid point of the digital elevation model according to the coordinate value of the observation grid point and the elevation value of the observation grid point includes: Constructing a ray parameter equation, discretizing the ray parameter equation to generate a ray path from the observation grid point to the target grid point, determining a sampling interval of the ray on the ray path according to the required accuracy, and obtaining coordinate values ​​of intermediate grid points on the ray path according to the sampling interval; Traverse each of the intermediate grid points along the ray path until all the intermediate grid points are processed: According to the coordinate value of the middle grid point, acquiring the elevation value of the middle grid point from the minimum visible height data; If the elevation value of the intermediate grid point is greater than the elevation value of the observation grid point, the elevation value of the intermediate grid point is used as the minimum visible height value of the intermediate grid point; If the elevation value of the intermediate grid point is less than or equal to the elevation value of the observation grid point, the elevation value of the observation grid point is used as the minimum visible height value of the intermediate grid point.

8. A visual line of sight calculation device based on a digital elevation model, characterized in that: include: A coordinate conversion module is used to obtain the geographic coordinates of the observation point and the target point, convert the geographic coordinates into the observation grid point and the target grid point based on the digital elevation model, and obtain the elevation value of the observation grid point; A pre-calculation module, used for calculating the minimum visible height value of each grid point of the digital elevation model according to the coordinate value of the observation grid point and the elevation value of the observation grid point, and taking the set of the minimum visible height values ​​corresponding to all the grid points as the minimum visible height data; A visibility judgment module is used to obtain the minimum visible height value corresponding to the target grid point from the minimum visible height data according to the coordinate value of the target grid point, and judge whether the elevation value of the observation grid point is greater than or equal to the minimum visible height value of the target grid point. If so, the target point and the observation point are visible, and if not, the target point and the observation point are not visible.

9. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the line of sight calculation method based on the digital elevation model described in any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program for executing the line of sight calculation method based on a digital elevation model according to any one of claims 1 to 7.

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