A helicopter landing site identification method based on high-resolution digital map

Abstract

The application discloses a kind of high-resolution digital map-based helicopter landing field identification method, step 1, identify the landing prohibited area in task area;Step 2, the high-resolution digital map of task area is grid divided;Step 3, according to the landing prohibited area and the terrain slope direction analysis to each grid, identify the alternative landing field;Step 4: the alternative landing field of adjacent spatial position is merged;Step 5: the information of each merged landing field is generated.The application can identify the landing area, design the blind landing field output rule, effectively support the field blind landing demand of helicopter.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ground map resource processing system design in the field of avionics, belongs to the field of aviation geographic information enhancement application, and particularly relates to a helicopter landing field identification method based on high-resolution digital maps, which meets the demand of helicopter blind landing in the wild. BACKGROUND

[0002] The ground map resource processing system is an important part of the ground end of the modern avionics system, is responsible for the multi-dimensional comprehensive processing and statistical analysis of geographic data obtained by various platform technologies, various sensing technologies, observation of different geographical locations and different times, and provides important data support for the airborne avionics display system.

[0003] As the main battle equipment of the aviation force, the helicopter has the advantages of flexible maneuvering, strong attack capability and strong coordination capability. In complex geographical environment, when encountering sudden situations such as disorientation, low visibility and wind shear, the pilot's environmental perception ability decreases and the operation load increases dramatically, and the landing safety faces severe challenges. For helicopter airport landing, due to the use of microwave landing system, instrument landing system, and even the way of ground personnel guiding landing by radio communication, the helicopter can be safely landed to a certain extent, but the premise is that special ground equipment is needed. If the helicopter lands in the wild, due to the influence of meteorological conditions, ground conditions, sand dust rolled up by the rotor and other factors, the visibility is reduced to different degrees, and the helicopter landing has a high risk. Therefore, how to quickly identify the helicopter landing area in the case of weakened environmental perception in the wild and guide the pilot to land safely is a problem to be solved by the aviation force.

[0004] The landing field identification method based on high-resolution geographic information (DEM, DOM, obstacle vector data) provided by the present application can extract the target area suitable for helicopter blind landing in the wild by analyzing geographic information data, and output in the form of a database according to rules, and further combined with landing planning technology, the pilot can be guided to land safely and efficiently in complex geographical and severe weather environments. SUMMARY

[0005] The present application provides a helicopter landing field identification method based on high-resolution digital maps, which analyzes the terrain slope, slope direction, geological properties and other indicators by processing and enhancing the application of high-resolution digital surface model data, high-resolution satellite images and obstacle vector data, and identifies the landing area by setting obstacle landing constraint areas, and designs a blind landing field output rule to effectively support the helicopter's blind landing demand in the wild.

[0006] The present application achieves the following technical solutions:

[0007] A helicopter landing field identification method based on high-resolution digital map, comprising the following steps:

[0008] Step 1, identify the landing prohibited area in the task area;

[0009] Step 2, grid division of high-resolution digital map of the task area;

[0010] Step 3, according to the landing prohibited area and the terrain slope analysis of each grid, identify the candidate landing field;

[0011] Step 4: merging the candidate landing fields adjacent in space position;

[0012] Step 5: generating information of each merged landing field.

[0013] Preferably, in step 1, the supervised classification method is used to extract the hard ground without open space in high-resolution satellite images, and then vectorization is performed to extract the hard ground boundary coordinates without open space as the landing prohibited area; based on the vector data of obstacles, a buffer zone is extended outward as the landing prohibited area.

[0014] Preferably, in step 2, the size of each grid is the minimum size of the landing field set by the user, and the adjacent grid is generated by translating horizontally by a length unit set by the user, and so on, so as to divide the horizontal direction into several grid areas, and then the vertical grid is generated by translating vertically by a width unit set by the user, and so on, so as to divide the vertical direction into several grids.

[0015] Preferably, step 3 comprises the following steps:

[0016] Step 31: using the Intersect algorithm in the GEOS library to judge the intersection relationship between the grid and the landing prohibited area, if there is intersection, the grid does not belong to the candidate landing field, otherwise, go to step 32 for further judgment;

[0017] Step 32: calculating the number of pixels in the horizontal and vertical directions in the grid according to the digital surface model data, traversing all the pixels in the grid, obtaining the ground height value of each pixel and the other 8 pixels corresponding to the geographical position in the 3x3 window range, and calculating the slope value and slope direction value of each position according to the fitting surface algorithm;

[0018] Step 33: the slope value and the slope direction value of the corresponding position of the pixel in the grid are obtained, and the maximum and minimum values of the slope and the slope direction in the grid are calculated; it is judged whether the slope value in the grid is less than the slope threshold value, if not, the grid is not the candidate landing site; if the slope value in the grid is less than the slope threshold value, it is continued to be judged whether the difference between the maximum slope value and the minimum slope value is less than the slope difference threshold value, and the difference between the maximum slope direction value and the minimum slope direction value is less than the slope difference threshold value, if yes, the grid is the candidate landing site, otherwise, the grid is not the candidate landing site.

[0019] Preferably, in step 4, firstly, the candidate landing site region merging is carried out in the horizontal direction, it is judged whether the current grid and the adjacent right grid meet the merging condition, the merging condition refers to that the average value of the grid slope and the average value of the right grid slope are less than the slope difference threshold value, and the average value of the grid slope direction and the average value of the right grid slope direction are less than the slope difference threshold value, if the condition is met, the figure is merged, and the vertex coordinate of the candidate landing site boundary is updated.

[0020] Then, the adjacent candidate landing site region merging is carried out in the vertical direction, it is judged whether the candidate landing site in the last row exists the intersection relationship with the current grid, if the current grid intersects with the candidate landing site in the last row and meets the merging condition, the merging condition refers to that the average value of the grid slope and the average value of the last row grid slope are less than the slope difference threshold value, and the average value of the grid slope direction and the average value of the last row grid slope direction are less than the slope difference threshold value, if the condition is met, the figure is merged, and the vertex coordinate of the landing site boundary is updated.

[0021] Preferably, in step 5, the longitude, latitude and elevation value of the landing site center position are calculated, the maximum slope value of the landing site is calculated, the ground flatness model is constructed through the normalization analysis of the slope and the slope direction, and the ground flatness of each landing site is calculated.

[0022]

[0023] Wherein, maxSlope is the maximum slope value, minSlope is the minimum slope value, maxDir is the maximum slope direction value, minDir is the minimum slope direction value, and fabs is the function of taking the absolute value of the floating point type.

[0024] The beneficial effects of the present application are:

[0025] The present application extracts the prohibited landing area based on the high-resolution satellite image, analyzes the ground slope and slope direction information by using the high-resolution digital surface model data, constructs the landing site recognition method by combining the site size and the terrain fluctuation condition requirement when the helicopter lands, extracts the boundary coordinate, the longitude, latitude, elevation and flatness information of the suitable helicopter landing site, and can assist the pilot to perform the landing task in the complex geographical environment, and improve the helicopter landing safety. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the process for determining alternative landing sites.

[0027] Figure 2 This is a flowchart illustrating a method for identifying helicopter landing sites based on high-resolution digital maps. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0029] The basic concept of this invention is to design a landing site identification method that considers landing site size, terrain undulation, surrounding obstacles, and human environmental factors. By performing land cover type classification analysis and terrain slope and aspect analysis on a high-resolution digital map (resolution not less than 15 meters), geographical environmental conditions information of candidate landing sites is obtained. Using the environmental conditions for helicopter landing as constraints, suitable landing sites are identified, meeting the requirements for blind landing of helicopters in complex geographical environments.

[0030] This embodiment illustrates a helicopter landing site identification method based on high-resolution digital maps, which is a software component within a ground map resource processing system. (See also...) Figure 2 As shown, it includes the following steps:

[0031] Step 1: Identify the prohibited landing areas in the task area and generate the boundary vertex coordinates of the prohibited landing areas.

[0032] Helicopters cannot safely land in certain areas; these areas are called prohibited landing zones. One type includes residential areas, rivers, and lakes where open, hard-surface terrain is unavailable. Another type refers to areas near obstacles such as high-voltage power line towers, wind turbines, and tower cranes, which pose a safety hazard to flight, and their surrounding areas are unsuitable for landing. A supervised classification method is used to extract residential areas, rivers, and lakes from high-resolution satellite imagery, which are then vectorized, and their boundary coordinates are extracted to define prohibited landing zones. Based on the vector data of obstacles such as high-voltage power line towers, wind turbines, and tower cranes, a buffer zone extending 100 meters outwards is defined as the prohibited landing zone. The coordinate information for both types of areas is converted into Shapefile files for storage.

[0033] Step 2: Divide the task area into a grid.

[0034] The size requirements of each helicopter landing site are different. The high-resolution digital map of the task area is horizontally and vertically divided into grids according to certain length and width. The size of each grid is the minimum size of the landing site set by the user. For example, the default length and width of the network are both 100 meters. Taking the length and width as a grid, the adjacent grid is generated by horizontally translating a length unit, and so on. The horizontal direction is divided into several grid areas. Then, the vertical grid is generated by vertically translating a width unit, and so on. The vertical direction is divided into several grids.

[0035] Step 3, according to the prohibited landing area and the terrain slope analysis of each grid, the candidate landing site is identified. Referring to Figure 1 As shown, comprising the following steps:

[0036] Step 31: using the Intersect algorithm in the GEOS library to judge the intersection relationship between the grid and the prohibited landing area. If there is an intersection, the grid does not belong to the candidate landing site. Otherwise, go to step 32 to continue to judge.

[0037] Step 32: according to the digital surface model data (DSM), the number of pixels in the horizontal and vertical directions of the grid is calculated. All the pixels in the grid are traversed to obtain the ground height value of each pixel and the corresponding geographical position of the other 8 pixels in the 3*3 window range. According to the fitting surface algorithm, the slope value and the slope direction value of each position are calculated. As shown in Table 1, the slope and slope direction of the center position e point are calculated.

[0038] e1 e2 e3 e4 e e5 e6 e7 e8

[0039] Table 1

[0040]

[0041] ei (i = 1, 2…8) represents the ground height value of the corresponding geographical position of the 8 pixels in Table 1, and d represents the grid spacing.

[0042]

[0043] Note: The unit of the calculation result is radian, which needs to be converted to degree, and then added by 90. The value represents the slope angle with the north direction as zero direction.

[0044] Step 33: Obtain the slope value and slope direction value of the pixel corresponding position in the grid, and calculate the maximum and minimum values of the slope and slope direction in the grid. Determine whether the slope value in the grid is less than the slope threshold value (default 3, unit degree). If not, the grid is not a candidate landing site. If so, continue to determine whether the difference between the maximum and minimum slope values is less than the slope difference threshold value (default 0.5, unit degree), and the difference between the maximum and minimum slope directions is less than the slope direction difference threshold value (default 1, unit degree). If so, the grid is a candidate landing site, otherwise, the grid is not a candidate landing site.

[0045] Step 4: Merge the candidate landing sites adjacent in spatial position.

[0046] After the identification of candidate landing sites in the task area is completed, the candidate landing sites adjacent in spatial position need to be merged. First, perform the candidate landing site region merging in the horizontal direction. Determine whether the current grid and the adjacent right grid meet the merging condition, which is that the average slope value of the grid and the average slope value of the right grid are less than the slope difference threshold value (default 0.5, unit degree), and the average slope direction value of the grid and the average slope direction value of the right grid are less than the slope direction difference threshold value (default 1, unit degree). If the conditions are met, perform the graph merging and update the vertex coordinates of the candidate landing site boundary. Then, perform the adjacent candidate landing site region merging in the vertical direction. Determine the candidate landing sites in the previous row that intersect with the current grid. If the current grid intersects with the candidate landing sites in the previous row and meets the merging condition (the merging condition is the same as above), perform the graph merging and update the vertex coordinates of the landing site boundary.

[0047] Step 5: Generate information of each merged landing site. Calculate the longitude, latitude and elevation value of the landing site center position, and calculate the maximum slope value of the landing site. Through the normalization analysis of the slope and slope direction, construct the ground flatness model and calculate the ground flatness of each landing site. The ground flatness can more intuitively reflect the undulating state of the ground surface, thereby improving the pilot's perception ability of the landing site surface environment. The specific method is as follows:

[0048]

[0049] Where maxSlope is the maximum slope value, minSlope is the minimum slope value, maxDir is the maximum slope direction value, minDir is the minimum slope direction value, and fabs is a function that takes the absolute value of a floating point type.

[0050] The output text format is shown in Table 2:

[0051] Total number of landing sites Landing site 1 Longitude Latitude Length Width Slope Flatness Landing site 2 Longitude Latitude Length Width Slope Flatness ……

[0052] Table 2

[0053] It can be understood that, for those ordinary skilled in the art, equivalent replacements or changes can be made according to the technical solutions and the inventive concept of the present application, and all the changes or replacements shall fall within the protection scope of the appended claims of the present application.

Claims

1. A method for identifying helicopter landing sites based on high-resolution digital maps, characterized in that... Includes the following steps: Step 1: Identify the no-landing zones within the mission area; Step 2: Divide the high-resolution digital map of the task area into grids; Step 3: Based on the prohibited landing zones and the topographic slope and aspect analysis of each grid, identify alternative landing sites, including the following steps: Step 31: Use the Intersect algorithm in the GEOS library to determine the intersection relationship between the grid and the no-landing zone. If there is an intersection, the grid is not a candidate landing site; otherwise, proceed to step 32 to continue the determination. Step 32: Calculate the number of pixels in the horizontal and vertical directions within the grid based on the digital surface model data. Traverse all pixels within the grid and obtain the surface height value of each pixel and the other 8 pixels within the 3×3 window range corresponding to the geographical location. Calculate the slope and aspect value of each location based on the fitted surface algorithm. Step 33: Obtain the slope and aspect values ​​of the corresponding positions of pixels within the grid, and calculate the maximum and minimum slope values ​​and the maximum and minimum aspect values ​​within the grid; Determine if the slope value within the grid is less than the slope threshold. If not, the grid is not a candidate landing site. If the slope value within the grid is less than the slope threshold, then further determine if the difference between the maximum and minimum slope values ​​of the grid is less than the slope difference threshold, and if the maximum and minimum aspect values ​​are less than the aspect difference threshold. If so, the grid is a candidate landing site; otherwise, the grid is not a candidate landing site. Step 4: Merge spatially adjacent candidate landing sites; Step 5: Generate information for each merged landing site.

2. The helicopter landing site identification method based on high-resolution digital maps according to claim 1, characterized in that... In step 1, a supervised classification method is used to extract hard ground areas that are not open in the high-resolution satellite imagery. These areas are then vectorized, and the boundary coordinates of the hard ground areas that are not open are extracted as prohibited landing areas. Based on the vector data of the obstacles, a buffer zone is extended outward as a prohibited landing area.

3. The method for helicopter landing site identification based on high-resolution digital maps according to claim 1, characterized in that... In step 2, the size of each grid is the minimum size of the landing site set by the user. The grid is translated horizontally by a user-defined length unit to generate adjacent grids. This process is repeated to divide the horizontal direction into several grid regions. Then, the grid is translated vertically by a user-defined width unit to generate vertical grids. This process is repeated to divide the vertical direction into several grid regions.

4. The method for helicopter landing site identification based on high-resolution digital maps according to claim 1, characterized in that... In step 4, firstly, the candidate landing site areas are merged in the horizontal direction. It is determined whether the current grid and the adjacent right grid meet the merging conditions. The merging conditions are that the average slope of the grid and the average slope of the right grid are less than the slope difference threshold, and the average slope aspect of the grid and the average slope aspect of the right grid are less than the slope aspect difference threshold. If the conditions are met, the graphs are merged and the vertex coordinates of the candidate landing site boundary are updated. Then, adjacent candidate landing site areas are merged in the vertical direction. The candidate landing sites in the previous row that intersect with the current grid are identified. If the current grid intersects with a candidate landing site in the previous row and meets the merging conditions, the merging conditions are: the average slope of the current grid is less than the average slope of the previous row grid and the average aspect of the current grid is less than the average aspect of the previous row grid. If the conditions are met, the graph is merged and the vertex coordinates of the landing site boundary are updated.

5. The method for helicopter landing site identification based on high-resolution digital maps according to claim 1, characterized in that... Step 5 includes calculating the longitude, latitude, and elevation of the landing site center location, calculating the maximum slope of the landing site, and constructing a ground smoothness model through normalized analysis of slope and aspect to calculate the ground smoothness of each landing site. Where maxSlope is the maximum slope value, minSlope is the minimum slope value, maxDir is the maximum aspect value, minDir is the minimum aspect value, and fabs is a function that takes the absolute value of a floating-point type.

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