Visibility Calculation Method, Device, Equipment and Medium Based on Digital Elevation Model

Abstract

An embodiment of the present invention provides a visibility calculation method, device, equipment and medium based on a digital elevation model. Among them, the method includes: obtaining the geographical coordinates of an observation point and a target point, converting the geographical coordinates into an observation grid point and a target grid point based on the digital elevation model, and obtaining the elevation value of the observation grid point; 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 grid points as the minimum visible height data; obtaining 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 determining 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. Since this solution uses the elevation information of the digital elevation model, the speed and efficiency of visibility calculation are improved.

Description

Technical Field

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

[0002] Visibility analysis refers to terrain analysis that takes a certain point as an observation point to study the visibility of a certain area. It is a technical method to use a digital elevation model to judge whether any two points on the terrain can be seen from each other.

[0003] Visibility analysis essentially belongs to the category of optimizing the terrain, such as setting up radar stations, transmitting stations of television stations, marine navigation, etc. In the military, such as arranging positions, setting up observation posts, real-time simulation systems, etc. The establishment of a digital elevation model provides a favorable basis for such analysis and can conveniently calculate each part that can be seen from an observation point. Identify the position of the observation point in the digital elevation model, draw a family of rays from this position, compare the elevations of each point (i.e., pixels in the elevation matrix) passed by the rays, and then the visibility of the target point can be analyzed and calculated.

[0004] Although the concept of visibility analysis is simple, it is very important for certain types of simulations, such as computer-generated forces (CGF) systems and sensor simulations. In the CGF simulation system, a large number of visibility judgments are required, and each visibility judgment may take a relatively long calculation time. Therefore, traditional visibility 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 calculation efficiency of visibility analysis and avoid the excessive determination calculation time caused by the large amount of raster data of the digital elevation model to improve the efficiency of real-time calculation and analysis is the key problem to be solved. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a visibility calculation method based on a digital elevation model to solve the technical problems of low accuracy and low calculation efficiency in visibility analysis in the prior art. The method includes:

[0006] Obtain the geographical coordinates of the observation point and the target point, convert the geographical coordinates into an observation raster point and a target raster point based on the digital elevation model, and obtain the elevation value of the observation raster point;

[0007] According to the coordinate value of the observation raster point and the elevation value of the observation raster point, calculate the minimum visible height value of each raster point of the digital elevation model, and use the set of the minimum visible height values corresponding to all the raster points as the minimum visible height data;

[0008] According to the coordinate value of the target grid point, obtain the lowest visible height value corresponding to the target grid point from the lowest visible height data, and determine whether the elevation value of the observation grid point is greater than or equal to the lowest visible height value of the target grid point. If so, the target point and the observation point are visible; if not, the target point and the observation point are not visible.

[0009] An embodiment of the present invention further provides a visibility calculation device based on a digital elevation model to solve the technical problems of low accuracy and low calculation efficiency in visibility analysis in the prior art. The device includes:

[0010] A coordinate conversion module, configured to obtain the geographical coordinates of an observation point and a target point, convert the geographical coordinates into an observation grid point and a target grid point based on a digital elevation model, and obtain the elevation value of the observation grid point;

[0011] A pre-calculation module, configured 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, and use the set of the lowest visible height values corresponding to all the grid points as the lowest visible height data;

[0012] A visibility judgment module, configured to obtain the lowest visible height value corresponding to the target grid point from the lowest visible height data according to the coordinate value of the target grid point, and determine whether the elevation value of the observation grid point is greater than or equal to the lowest visible height value of the target grid point. If so, the target point and the observation point are visible; if not, the target point and the observation point are not visible.

[0013] An embodiment of the present invention further provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the above-mentioned any visibility calculation method based on a digital elevation model is implemented to solve the technical problems of low accuracy and low calculation efficiency in visibility analysis in the prior art.

[0014] An embodiment of the present invention further provides a computer-readable storage medium, which stores a computer program for executing the above-mentioned any visibility calculation method based on a digital elevation model to solve the technical problems of low accuracy and low calculation efficiency in visibility analysis in the prior art.

[0015] Compared with the prior art, the at least one technical solution adopted in the embodiments of the present specification can achieve at least the following beneficial effects:

[0016] The visual communication calculation method of the embodiment of the present invention pre-calculates the minimum visible height data and uses this data for real-time visibility analysis, avoiding the problem of a large amount of calculation required for each visibility judgment, thereby greatly improving the speed and efficiency of visibility calculation and effectively enhancing the real-time performance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0018] Figure 1 is a flowchart of a visibility calculation method based on a digital elevation model provided by an embodiment of the present invention;

[0019] Figure 2 is a structural block diagram of a computer device provided by an embodiment of the present invention;

[0020] Figure 3 is a structural block diagram of a visibility calculation device based on a digital elevation model provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following will describe the embodiments of the present application in detail with reference to the drawings.

[0022] The following specific examples illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content 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 manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments in the present application belong to the scope of protection of the present application.

[0023] In an embodiment of the present invention, a visibility calculation method based on a digital elevation model is provided, as Figure 1 shown, the method includes:

[0024] Step S101: Obtain the geographical coordinates of the observation point and the target point, convert the geographical coordinates into an observation grid point and a target grid point based on the digital elevation model, and obtain the elevation value of the observation grid point;

[0025] Step S102: According to the coordinate values of the observed grid points and the elevation values of the observed grid points, calculate the minimum visible height value of each grid point of the digital elevation model (the minimum visible height value is the minimum height value required for line-of-sight between the grid point and the target grid point), and use the set of the minimum visible height values corresponding to all the grid points as the minimum visible height data;

[0026] Step S103: According to the coordinate values of the target grid point, obtain the minimum visible height value corresponding to the target grid point from the minimum visible height data, and determine whether the elevation value of the observed 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 observed point are visible; if not, the target point and the observed point are not visible.

[0027] Specifically, when implementing, the following steps are used to calculate the minimum visible height value of each grid point of the digital elevation model according to the coordinate values of the observed grid points and the elevation values of the observed grid points:

[0028] Construct a ray parameter equation, discretize the ray parameter equation to generate a ray path from the observed grid point to the target grid point, determine the sampling interval of the ray on the ray path according to the required accuracy, and obtain the coordinate values of the intermediate grid points on the ray path according to the sampling interval; traverse each intermediate grid point along the ray path until all the intermediate grid points are processed:

[0029] 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 observed 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 observed grid point, use the elevation value of the observed grid point as the minimum visible height value.

[0030] Specifically, point-by-point ray traversal draws a ray from the observation point (i.e., the observed point) to each target point, and checks whether the elevation of all intermediate points (i.e., the sampling points between the observed point and the target point on the ray path) on the ray path blocks the line of sight. If the elevation of all intermediate points does not exceed the line-of-sight height, the target point is visible. Ensuring accuracy through point-by-point inspection is applicable to scenarios with high precision requirements, but the computational complexity is O(n 2 ), and it is applicable to medium and small-scale data based on digital elevation models. Once an intermediate point is found to block the view, subsequent inspections are immediately stopped. Manhattan distance or the number of steps can also be used instead of Euclidean distance to accelerate the calculation (accuracy needs to be weighed). Each target point is processed independently, which is suitable for parallelization to improve efficiency.

[0031] In specific implementation, the following steps are adopted to calculate the minimum visible height value of each grid point of the digital elevation model based on the coordinate value of the observed grid point and the elevation value of the observed grid point:

[0032] Based on the coordinate value of the observed grid point, with the observed grid point as the center, all the grid points are divided into different radial profiles. Each grid point belongs to at least one of the radial profiles. After sorting the grid points in each radial profile, a sorted radial profile group is generated; the invisible grid points in each radial profile are marked and the invisible grid points are deleted from the sorted radial profile group; for each radial profile in the sorted radial profile group, in the order of increasing distance between the grid point and the observed grid point, the global maximum elevation angle slope relative to the observed grid point is calculated, and based on the global maximum elevation angle slope and the elevation value of the observed grid point, the minimum visible height value of each grid point is calculated; taking each grid point as a unit, all the radial profiles are traversed, the minimum visible height value of each grid point in each radial profile is obtained, at least one minimum visible height value corresponding to each grid point is obtained, and the maximum value among at least one minimum visible height value is used as the minimum visible height value of each grid point.

[0033] In specific implementation, the following steps are adopted to divide all the grid points into different radial profiles and generate a sorted radial profile group after sorting the grid points in each radial profile:

[0034] With the observed grid point as the center and at intervals of a set angular step size, the digital elevation model is divided into multiple radial profiles; all the grid points in the digital elevation model are traversed, the azimuth angle of each grid point is calculated through the coordinate value of each grid point, and the azimuth angle is mapped to 0 to 360°, generating a mapped azimuth angle; according to the mapped azimuth angle and the angular step size, each grid point is assigned to the radial profile closest to the grid point, generating a radial profile group; in the radial profile group, the grid points are sorted in the order of increasing distance from the observed grid point, generating a sorted radial profile group.

[0035] In specific implementation, the following steps are adopted to calculate the global maximum elevation angle slope relative to the observed grid point and calculate the minimum visible height value of each grid point based on the global maximum elevation angle slope and the elevation value of the observed grid point:

[0036] Calculate the total distance between each of the grid points and the observed grid point; obtain the intermediate grid points between the connection lines of the grid points and the observed grid point, and calculate the distance between each of the intermediate grid points and the observed grid point; calculate the elevation slope of the intermediate grid point relative to the observed grid point according to the distance, the elevation value of the observed 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 lowest visible height of each of the grid points through the total distance, the global maximum elevation slope, and the elevation value of the observed grid point.

[0037] Specifically, convert the point-by-point ray traversal (with a complexity of O(n 2 )) into a radial profile scan, and utilize the maximum elevation tracking and spatial coherence to reduce the complexity to O( ) (m is the number of radials, which is usually much smaller than n 2 ). The key is to avoid repeated traversal of intermediate points when pre-computing the lowest visible height of each target point.

[0038] In one embodiment, first, divide the polar coordinates and perform a radial profile scan. Divide the digital elevation model into radial profiles at multiple angles around the observed point (for example, one profile per 1 degree, a total of 360. The smaller the radial interval, the higher the accuracy, but the computational amount increases. Usually, 1° - 5° is taken to balance efficiency and accuracy); within each profile, sort the grid points in ascending order of the distance from the observed point.

[0039] Secondly, perform single-profile processing and maximum elevation tracking. For each radial profile, process the points in increasing order of distance, dynamically maintain the current maximum elevation slope, and quickly deduce the lowest visible height of subsequent points.

[0040] For the grid point P (with a total distance from the observed point of ) in the profile, its lowest height depends on the maximum elevation slope of all the intermediate grid points on the path: . Among them, P is the grid point in the radial profile, is the lowest visible height of point P, d is the distance between all the intermediate grid points on the path and the observed point, is the elevation of the observed grid point, is the elevation value of the intermediate grid point.

[0041] Since each grid point may belong to multiple radial profiles, take the maximum value of the calculated for each of its profiles as the final lowest visible height value to ensure that all paths are covered.

[0042] After pre-computing to generate the lowest visible height data, during the process of analyzing line-of-sight, the real-time analysis can obtain the result by only querying and comparing the lowest visible height data. In actual use, if the observation point moves, it is necessary to re-pre-compute to generate the lowest visible height data, and the data calculation can be optimized by incrementally updating the affected cross-sections.

[0043] The overall complexity of pre-computation using the above method is , and the complexity of real-time analysis is , reducing the computational complexity from O(n 2 ) to pre-computation and real-time query of

[0044] is suitable for real-time line-of-sight analysis of large-scale satellite terrain data (such as military reconnaissance simulation, base station planning, etc.).

[0045] Set a preset maximum visible distance according to the earth's curvature, atmospheric refraction, and the sensing range of the sensor. If the relative distance between the target grid point and the observation grid point is greater than the preset maximum visible distance, mark the current target grid point as an invisible target grid point; or, if the elevation value of the target grid point 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 angle 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 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, then mark the target grid point as an invisible target grid point.

[0046] Specifically, in order to introduce a heuristic algorithm to quickly exclude obviously invisible target points and reduce the amount of precise calculation, the following steps are used to mark the invisible grid points in each of the radial sections:

[0047] Obtain the historical minimum elevation angle slope of each of the radial profiles based on the historical elevation angle data, where the historical elevation angle data is the elevation angle slope of the target grid point calculated during the previous line-of-sight calculation; if the elevation angle slope of the target grid point is less than the historical minimum elevation angle slope, mark the target grid point as an invisible target grid point.

[0048] Specifically, filter out ultra-distant points quickly by distance (ultra-distant points cannot be visible due to the limitations of the earth's curvature, atmospheric refraction, or sensor range). That is, if the relative distance between the grid target point and the observation point grid is greater than the preset maximum visible distance, directly mark it as invisible.

[0049] Calculate the influence of the earth's curvature on the line of sight. If the elevation of the target point , directly mark it as invisible. , where 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.

[0050] Based on the directional slope statistics, filter the lower limit of the elevation angle. Pre-statistically calculate the historical minimum elevation angle of each angular profile. If it is lower than this value, it is blocked by the terrain (i.e., ).

[0051] In addition, it is also possible to based on pre-calculated peak points. If the target point is behind the terrain barrier in a certain direction and its elevation is lower than the barrier point (the maximum elevation angle point), then it is directly invisible.

[0052] In this embodiment, a computer device is provided. As Figure 2 shown, it includes a memory 201, a processor 202, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, it implements any of the above line-of-sight calculation methods based on the digital elevation model.

[0053] Specifically, this computer device can be a computer terminal, a server, or a similar computing device.

[0054] In this embodiment, a computer-readable storage medium is provided. The computer-readable storage medium stores a computer program that executes any of the above line-of-sight calculation methods based on the digital elevation model.

[0055] Specifically, a computer-readable storage medium includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. The information can be computer-readable instructions, data structures, program modules, 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 technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassette tapes, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information accessible by a computing device. As defined herein, a computer-readable storage medium does not include transitory computer-readable media, such as modulated data signals and carrier waves.

[0056] Based on the same inventive concept, an embodiment of the present invention also provides a line-of-sight calculation device based on a digital elevation model, as described in the following embodiments. Since the principle of the line-of-sight calculation device based on a digital elevation model for solving problems 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 elaborated. As used hereinafter, the term "unit" or "module" can be a combination of software and / or hardware that can achieve a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, implementation in hardware, or a combination of software and hardware is also possible and contemplated.

[0057] Figure 3 is a structural block diagram of the line-of-sight calculation device based on a digital elevation model according to an embodiment of the present invention, as Figure 3 shown, including: a coordinate conversion module 301, a pre-calculation module 302, and a line-of-sight judgment module 303. The following describes this structure.

[0058] 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 an observation grid point and a target grid point based on the digital elevation model, and obtain the elevation value of the observation grid point;

[0059] 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 use the set of the minimum visible height values corresponding to all the grid points as the minimum visible height data;

[0060] The visual connection judgment module 303 is configured to obtain the lowest visible height value corresponding to the target grid point from the lowest visible height data according to the coordinate value of the target grid point, and determine whether the elevation value of the observation grid point is greater than or equal to the lowest visible height value of the target grid point. If so, the target point and the observation point are visible; if not, the target point and the observation point are not visible.

[0061] In one embodiment, the pre-calculation module includes:

[0062] The profile division unit is configured to divide all the grid points into different radial profiles with the observation grid point as the center according to the coordinate value of the observation grid point. Each grid point belongs to at least one radial profile. After sorting the grid points in each radial profile, a sorted radial profile group is generated;

[0063] The invisible grid point deletion unit is configured to mark the invisible grid points in each radial profile and delete the invisible grid points from the sorted radial profile group;

[0064] The lowest visible height calculation unit is configured to, for each radial profile in the sorted radial profile group, calculate the global maximum elevation angle slope relative to the observation grid point in the order of increasing distance between the grid points and the observation grid point, and calculate the lowest visible height value of each grid point according to the global maximum elevation angle slope and the elevation value of the observation grid point;

[0065] The first lowest visible height set generation unit is configured to traverse all the radial profiles with each grid point as a unit, obtain the lowest visible height values of each grid point in each radial profile, obtain at least one lowest visible height value corresponding to each grid point, and use the maximum value among the at least one lowest visible height values as the lowest visible height value of each grid point.

[0066] In one embodiment, the profile division unit is configured to divide the digital elevation model into multiple radial profiles with the observation grid point as the center at intervals of a set angular step; traverse all the grid points in the digital elevation model, calculate the azimuth angle of each grid point through the coordinate value of each grid point, and map the azimuth angle to 0 to 360°, generating a mapped azimuth angle; allocate each grid point to the radial profile closest to the grid point according to the mapped azimuth angle and the angular step, generating a radial profile group; in the radial profile group, sort the grid points in ascending order of the distance from the observation grid point, generating a sorted radial profile group.

[0067] In one embodiment, the minimum visible height value calculation unit is configured to calculate the total distance between each of the grid points and the observation grid point; obtain the intermediate grid points between the connection lines of the grid points and the observation grid point, and calculate the distance between the intermediate grid points and the observation grid point; calculate the elevation angle 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 of the grid points; compare the elevation angle slopes of all the intermediate grid points, and take the maximum elevation angle slope as the global maximum elevation angle slope; calculate the minimum visible height of each of the grid points through the total distance, the global maximum elevation angle slope, and the elevation value of the observation grid point.

[0068] In one embodiment, the invisible grid point deletion unit is configured to set a preset maximum visible distance according to the earth curvature, atmospheric refraction, and the sensing limit range of the sensor. If the relative distance between the target grid point and the observation grid point is greater than the preset maximum visible distance, mark the current target grid point as an invisible target grid point; or, if the elevation value of the target grid point , mark the target grid point as an invisible target grid point, where 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 angle point of the radial profile 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 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, then mark the target grid point as an invisible target grid point.

[0069] In one embodiment, the invisible grid point deletion unit is further configured to obtain the historical minimum elevation angle slope of each of the radial profiles according to the historical elevation angle data , where the historical elevation angle data is the elevation angle slope of the target grid point calculated during the previous visual communication calculation process; if the elevation angle slope of the target grid point is less than the historical minimum elevation angle slope , mark the target grid point as an invisible target grid point.

[0070] In one embodiment, the pre-calculation module includes:

[0071] A path generation unit, configured 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 a required accuracy, and obtain coordinate values of intermediate grid points on the ray path according to the sampling interval;

[0072] A path traversal unit, configured to traverse each of the intermediate grid points along the ray path until all the intermediate grid points are processed:

[0073] An elevation acquisition unit, configured to obtain the elevation value of the intermediate grid point from the lowest visible height data according to the coordinate value of the intermediate grid point;

[0074] A lowest visible height calculation unit, configured to use the elevation value of the intermediate grid point as the lowest 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;

[0075] A second lowest visible height set generation unit, configured to use the elevation value of the observation grid point as the lowest 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.

[0076] The embodiments of the present invention achieve the following technical effects:

[0077] The line-of-sight calculation method of the embodiments of the present invention pre-calculates the lowest visible height data and uses the data for real-time line-of-sight analysis, avoiding the problem of a large amount of calculations required for each line-of-sight judgment, thereby greatly improving the speed and efficiency of line-of-sight calculation and effectively enhancing the real-time performance of the system; the line-of-sight calculation method of the embodiments of the present invention can effectively avoid the problem of too long determination calculation time caused by too large raster data volume based on the digital elevation model, thereby further improving the efficiency of real-time calculation and analysis, being simple and efficient, without the need for complex equal-area cutting processing and equal-height processing, and being able to obtain a more accurate line-of-sight analysis result.

[0078] Obviously, those skilled in the art should understand that each module or each step of the above embodiments of the present invention can be implemented by a general-purpose computing device. They can be concentrated on a single computing device or distributed on a network composed of multiple computing devices. Optionally, they can be implemented by program codes executable by the computing device. Thus, 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 here, or they can be separately fabricated into individual integrated circuit modules, or multiple modules or steps among them can be fabricated 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.

[0079] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various changes and modifications can be made to the embodiments of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within 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; 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; 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: 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.

3. The method for calculating visibility based on a digital elevation model according to claim 1, 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.

4. The method for calculating visibility based on a digital elevation model according to claim 1, 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.

5. The method for calculating visibility based on a digital elevation model according to claim 1, 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.

6. The method for calculating visibility based on a digital elevation model according to any one of claims 1 to 5, 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.

7. 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 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; Pre-calculation modules, including: 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; A first minimum visible height set generating unit is configured 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 use the maximum value of at least one minimum visible height value as the minimum visible height value of each grid point; 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.

8. 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 6 is implemented.

9. 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 6.

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