Method for extracting landform in wind disaster assessment model of power transmission line

Abstract

The invention discloses a landform extraction method in a power transmission line wind disaster assessment model, and relates to the technical field of power transmission line wind disaster assessment, and the method comprises the following steps: 1, collecting geographic data; step 2, data processing; 3, topographic factor mathematical expression; and 4, FME-based topographic factor parameter extraction. According to the terrain and landform extraction method in the power transmission line wind disaster evaluation model, fine extraction of complex terrain and landform elements in a power transmission line corridor is realized based on high-resolution remote sensing image data in combination with a digital elevation model (DEM) and a geographic information system (GIS) technology by adopting advanced technologies such as multi-scale analysis and object-oriented classification; the method provides reliable data support for accurately evaluating the wind disaster risk of the power transmission line, has the advantages of high automation degree, high precision, high efficiency and the like, and can be widely applied to the fields of wind disaster risk evaluation of the power transmission line, line site selection, disaster prevention and reduction and the like.

Description

Technical Field

[0001] The invention relates to the technical field of databases, and in particular to a method for extracting topography in a wind disaster assessment model for a power transmission line. Background Art

[0002] As the scale of power grid continues to expand, the safe operation of transmission lines has received more and more attention. Wind disasters are one of the important factors affecting the safe operation of transmission lines. Accurately assessing the wind disaster risk of transmission lines is of great significance to ensuring the safe and stable operation of power grids. In the wind disaster assessment model of transmission lines, topography is an important factor, which has a significant impact on the distribution of wind fields and the size of wind speed. Therefore, how to accurately extract the topographic information along the transmission line is a key issue in the wind disaster assessment of transmission lines.

[0003] The existing technology has the following shortcomings in the process of topography extraction in the transmission line wind disaster assessment model:

[0004] (1) Insufficient accuracy: Some methods have low extraction accuracy for complex terrain and landforms, making it difficult to accurately reflect the impact of terrain on the wind field.

[0005] (2) Inefficiency: Some methods require large amounts of computation and long processing time, making it difficult to meet the needs of large-scale and rapid evaluation.

[0006] (3) Poor applicability: Some methods have high requirements on data type and resolution, poor applicability, and are difficult to promote and apply. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a method for extracting topography and landforms in a transmission line wind disaster assessment model, which solves the existing problems.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for extracting topography and landforms in a wind disaster assessment model for a power transmission line, comprising the following steps:

[0009] Step 1: Collect geographic data: collect terrain factor information, water system data, average wind direction data and soil data of the transmission line;

[0010] Step 2: Data processing: transform the elevation data into WGS84 coordinates, and then project them into plane map coordinates;

[0011] Step 3: Mathematical expression of terrain factors: Determine terrain type, altitude, slope, aspect, land cover type and water density in the plane map coordinate projection;

[0012] Step 4: Extract terrain factor parameters based on FME: Extract land cover type and ground inclination parameters based on FME.

[0013] Preferably, the terrain factor information includes: elevation, terrain type, slope, slope aspect, ground inclination, hillside, terrain relief, ridge line, valley line, land cover type, water body density and water body distance;

[0014] The elevation, terrain type, slope, slope aspect, ground inclination, hillside, terrain relief, ridge line, valley line, etc. are calculated through DEM data of the transmission line;

[0015] The surface coverage type and water area density are calculated by superimposing the surface coverage type data of the transmission line and the longitude and latitude information of the tower;

[0016] The water body distance is calculated by superimposing water system data on transmission line data.

[0017] Preferably, the water system data adopts the terrain vector data disclosed by the National Map, the average wind direction data is calculated using the free meteorological observation data released by the Meteorological Data Center of the China Meteorological Administration or the European Space Agency, and the soil data is obtained using the World Soil Database.

[0018] Preferably, the plane map coordinate projection adopts Mercator projection. When the data of WGS84 coordinate system is converted into Mercator projection, the following simplified formula is used:

[0019]

[0020] Where x and y are the coordinates of the plane coordinate system after the projection is unfolded into a plane diagram, R is the radius of the standard sphere specified in WGS84 (m), λ, is the angle parameter of WGS84 coordinate system;

[0021] After the projection is completed, various types of terrain attribute information can be extracted and assigned.

[0022] Preferably, the terrain type uses a surface water physical simulation analysis method based on DEM, and the terrain is divided into ridges, valleys, passes, windward slopes and leeward slopes, and flat land. According to the physical laws of surface water, the cumulative runoff of the surface grid is calculated. The ridge is used as a watershed, and its cumulative runoff should be zero, so the watershed is obtained by connecting points with zero cumulative runoff. The surface elevation data is inverted, and the watershed is divided in the same way to obtain the watershed under the positive terrain, that is, the valley. The pass is the intersection of the watershed and the watershed.

[0023] The area except for the ridge, valley and pass terrain is the hillside area. The windward slope and leeward slope are extracted as follows: extract each hillside unit to be identified, calculate the slope direction of each hillside unit cyclically, search for the meteorological station closest to the grid unit position for each hillside unit to be divided, calculate the multi-year summer average wind direction of the meteorological station, compare the slope direction and summer wind direction, and divide the hillside unit with an angle between the slope direction and the wind direction within 90° into the windward slope, otherwise it is the leeward slope;

[0024] The steepness at each pixel is read through the geographic information system, that is, the percentage of the elevation difference between two points and the horizontal distance, and the area with a steepness of 0-2% is defined as flat land.

[0025] Preferably, the altitude is one of the basic information contained in the digital elevation data, and is approximately represented by the projected Z-axis coordinate value;

[0026] The slope reflects the inclination of the slope and is defined as the tangent value of the inclination angle of the slope. The slope is expressed in degrees and is numerically equal to the angle between the normal vector of the surface unit passing through a certain point and the z-axis. The formula for extracting the slope is as follows:

[0027]

[0028] In the formula, f x is the rate of change of elevation in the x direction, f y is the rate of change of elevation in the y direction;

[0029] The slope direction is defined as follows: 0° is defined as the true north direction, and the angle between the clockwise direction and the true north direction represents the slope direction. The slope direction calculation formula is as follows:

[0030]

[0031] The slope obtained by the above formula has positive and negative angles with the x-axis, so it is necessary to calculate the slope according to f x and f y Further judge the positive or negative;

[0032] The data source of the land cover type adopts FROM-GLC10, and the land cover type is remapped into water bodies, forest land, grassland, cultivated land and urban land;

[0033] The water area density is defined as the ratio of the water area within a certain radius around the tower to the total area, which is used to analyze the impact of water on lightning disasters. The calculation formula for water area density is: water area density = water area ÷ total area of ​​the region × 100%.

[0034] Preferably, in step 4, the calculation of the ground cover type extraction step is performed based on the tower point file and the ground cover type grid file and the coordinate system is the cgcs2000 geographic coordinate system, including:

[0035] S11: Read the tower point xls, filter out the longitude outside China (according to China's geographical scope), add the serial number when reading, so as to restore the sorting when outputting the results, create point features according to the longitude and latitude, and perform projection transformation;

[0036] S12: Read the land cover type geotif data and project it;

[0037] S13: using the point feature and the raster overlay converter, obtaining the land use raster pixel value corresponding to the tower point, and passing the pixel value to the point feature as the land use classification code;

[0038] S14: Calculate the XY projection coordinate value of the tower and create text content output in txt format;

[0039] S15: Output the extraction result as txt text.

[0040] Preferably, in step 4, the calculation of the ground inclination extraction step is performed based on the tower point file and the block elevation DEM file and the coordinate system is the cgcs2000 geographic coordinate system, including:

[0041] 1) Read the tower point xls, filter out the longitude outside China (based on China's geographical scope), add a serial number when reading, to restore the order when outputting the results, create point features based on longitude and latitude, and perform projection transformation;

[0042] 2) The pole tower points are connected into power lines. When connecting, they are interrupted according to the group number attribute to prepare for calculating the direction of the power line and obtaining the vertical direction section of the pole tower; at the same time, the attributes are deleted and the power line number is added;

[0043] 3) Each power line is split into two segments with two nodes to facilitate the calculation of the direction of each power line segment, and numbers are added to the small segments, and the starting coordinates of the small segments are calculated as the starting point for subsequent rotation;

[0044] 4) Take the last small line segment and rotate it 180 degrees with the end point as the starting point to make it an extension of the last line segment;

[0045] 5) Rotate each small line segment 90 and 270 degrees to the left and mark left and right;

[0046] 6) The two small line segments on the left and right are respectively cut to 120, 90, 60, and 30 meters to obtain eight groups of cross-sectional projection line segments of different lengths perpendicular to the direction of travel of the power line;

[0047] 7) Arrange, number, calculate the length of the cross-section projection line segment group, split it into individual nodes, and add the cross-section line segment group number;

[0048] 8) Import dem, mosaic and merge, and project to 3-degree zoning;

[0049] 9) Use the point and grid overlay converter to obtain the node elevation, arrange the nodes in global order, make the tower point in front of the end point of the cross-section projection line, and obtain the elevation value of the previous element as the starting elevation of the current element;

[0050] 10) Delete redundant attributes, distinguish the tower point and the distal point according to the cross-section number value of the cross-section point, calculate the elevation difference according to the elevation value of the distal point and the elevation value of the tower point, and calculate the inclination value by inverse trigonometric function based on the cross-section length;

[0051] 11) Aggregate the cross-section point elements and merge the attributes by tower, and calculate the absolute average of the eight inclination angles. Then calculate the average values ​​for the left and right directions respectively, and then convert them into tower point elements;

[0052] 12) Use the read original tower point elements and the tower point elements with target attributes such as inclination angle restored according to the projection coordinate values ​​to search for the nearest elements, append the calculation results to the original tower point elements, and perform attribute sorting and element sorting operations;

[0053] 13) Output the calculation results as xls table.

[0054] Beneficial Effects

[0055] The present invention provides a method for extracting topography and landforms in a transmission line wind disaster assessment model. Compared with the prior art, it has the following beneficial effects:

[0056] 1. The terrain and geomorphic extraction method in the transmission line wind disaster assessment model is based on high-resolution remote sensing image data, combined with digital elevation model (DEM) and geographic information system (GIS) technology, and adopts multi-scale analysis, object-oriented classification and other advanced technologies to achieve refined extraction of complex terrain and geomorphic elements in the transmission line corridor, providing reliable data support for accurate assessment of transmission line wind disaster risks. It has the advantages of high degree of automation, high precision and high efficiency, and can be widely used in transmission line wind disaster risk assessment, line site selection and disaster prevention and mitigation.

[0057] 2. The terrain extraction method in the transmission line wind disaster assessment model effectively improves the accuracy of terrain extraction through improved edge detection algorithm and data fusion technology, more accurately reflects the impact of terrain on the wind field, and significantly shortens data processing time and improves work efficiency through parallel computing technology and efficient algorithms. It has relatively low requirements for data type and resolution, has strong applicability and promotion value, realizes the automation of terrain data extraction, reduces the degree of manual intervention, and reduces human errors. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 It is a schematic diagram of the method flow of the present invention;

[0059] Figure 2 It is a schematic diagram of the surface water physical simulation analysis method of the present invention;

[0060] Figure 3 It is a schematic diagram of the surface unit slope of the present invention. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] See also Figure 1-3 , the present invention provides two technical solutions:

[0063] The first implementation mode: A method for extracting topography and landforms in a transmission line wind disaster assessment model, comprising the following steps:

[0064] Step 1: Collect geographic data: Collect terrain factor information, water system data, average wind direction data and soil data of the transmission line.

[0065] Among them, elevation, terrain type, slope, slope aspect, ground inclination, hillside, terrain undulation, ridge line, valley line, etc. are calculated through DEM data of transmission lines; surface cover type and water density are calculated by superimposing the surface cover type data of transmission lines on the longitude and latitude information of towers; water body distance requires water system data superimposed on transmission line data to be calculated.

[0066] The water system data adopts the terrain vector data disclosed by the National Tiantu Map, the average wind direction data is calculated using the free meteorological observation data released by the Meteorological Data Center of the China Meteorological Administration or the European Space Agency, and the soil data is obtained using the World Soil Database.

[0067] The present invention uses digital elevation data with a spatial resolution of 30m from the geographic information cloud space platform, which will be divided into 30m×30m grids, and the z-axis coordinate value of each grid is used as the elevation of the area. DEM (Digital Elevation Model) is a data set that uses three-dimensional spatial coordinates to represent the spatial position of points. It contains rich terrain and landform information and has the characteristics of image, intuitiveness, and accuracy. Based on DEM data, using neighborhood analysis, distance analysis and other means to calculate terrain parameter values ​​with certain formulas, it is possible to obtain terrain factors such as slope, slope aspect, and surface curvature that reflect local surface characteristics. The rapid development of DEM data and GIS technology has made terrain and landform analysis based on digital elevation models gradually become a research hotspot. This project analyzes and extracts terrain feature parameters based on digital elevation data.

[0068] Commonly used digital elevation data resolutions include 30m×30m, 90m×90m, 1km×1km, etc. For the selection of elevation data resolution, theoretically, the higher the data resolution, the richer the terrain content and details it contains, and the more accurately it can reflect the actual terrain conditions. However, in actual applications, it is necessary to consider that for data with too high a resolution, the data volume will increase exponentially. If the research area is large, the computer overhead will be huge and very time-consuming. In addition, the local terrain scale studied in this project is between hundreds of meters and kilometers. The data with a resolution of 30m is within the scale of the local terrain and is much higher than the spatial accuracy of the soil database. At the same time, the data volume is relatively reasonable and meets the requirements of terrain feature analysis in this study.

[0069] The distribution and changes of land cover reflect the interaction between humans and nature, and are basic information in the fields of ecological environment monitoring and climate change. The land cover type data used in this project comes from FROM-GLC10, a 10m resolution land cover type product developed by Professor Gong Peng of the Department of Earth Sciences of Tsinghua University and made publicly available to the world. The data training contains approximately 340,000 samples of different sizes (from 30m×30m to 500m×500m), covering approximately 93,000 sample points worldwide. Compared with the previous generation of 30m resolution products, the overall accuracy of FROM-GLC10 is 72.76%, which is comparable to the accuracy of FROM-GLC30, but the results of FROM-GLC10 provide more spatial details. FROM-GLC10 divides land cover types into 10 categories.

[0070] The terrain data is shown in the table:

[0071]

[0072] Step 2: Data processing: Transform the elevation data into WGS84 coordinates and then project them into plane map coordinates.

[0073] The plane map coordinate projection adopts Mercator projection. When the data of WGS84 coordinate system is converted into Mercator projection, the following simplified formula is used:

[0074]

[0075] Where x and y are the coordinates of the plane coordinate system after the projection is unfolded into a plane diagram, R is the radius of the standard sphere specified in WGS84 (m), λ, is the angle parameter of WGS84 coordinate system;

[0076] After the projection is completed, various types of terrain attribute information can be extracted and assigned.

[0077] Step 3. Mathematical expression of terrain factors: Determine the terrain type, altitude, slope, aspect, land cover type and water density in the plane map coordinate projection.

[0078] The terrain type adopts the surface water physical simulation analysis method based on DEM, and divides the terrain into ridges, valleys, passes, windward slopes and leeward slopes, and flat land. According to the physical laws of surface water, the cumulative runoff of the surface grid is calculated. The ridge is used as the watershed, and its cumulative runoff should be zero, so the watershed is obtained by connecting the points with zero cumulative runoff. The surface elevation data is inverted (a large value is subtracted from the elevation data), and the watershed is divided in the same way to obtain the watershed under the positive terrain, that is, the valley. The pass is the intersection of the watershed and the watershed.

[0079] The principle of this terrain surface flow physical simulation analysis based on DEM is: for the ridge line, since it is also a watershed line, then for those grids on the watershed line, since the nature of the watershed line is the origin of the water flow, after the surface runoff simulation calculation, the water flow direction of these grids should only have an outflow direction without an inflow direction, that is, the cumulative flow of the grid is zero. By extracting the grid with zero cumulative flow value, the watershed line can be obtained, and the ridge line can be obtained; for the valley line, since it has the nature of water collection, the extraction of the valley line can use the characteristics of reverse terrain, that is, using a larger value to subtract the original DEM data, and obtain terrain data that is completely opposite to the original terrain, that is, the ridge in the original DEM becomes the valley of the negative terrain, and the valley in the original DEM becomes the ridge in the negative terrain. Then, the valley line can be extracted in the negative terrain using the method of extracting the ridge line. The schematic diagram of the extraction result is shown as follows Figure 2 shown.

[0080] Extraction of windward slope and leeward slope: The area except ridges, valleys and passes in the study area is defined as the hillside area. The extraction method of windward slope and leeward slope is as follows: extract each hillside unit to be identified, cyclically calculate the slope direction of each hillside unit, for each hillside unit to be divided, search for the meteorological station closest to the grid unit, calculate the multi-year summer average wind direction of the meteorological station, compare the slope direction and summer wind direction, and divide the hillside unit with an angle between the slope direction and the wind direction within 90° into the windward slope, otherwise it is a leeward slope.

[0081] The steepness at each pixel is read through the geographic information system, that is, the percentage of the elevation difference between two points and the horizontal distance, and the area with a steepness of 0-2% is defined as flat land.

[0082] The altitude is one of the basic information contained in the digital elevation data, and is approximately represented by the projected Z-axis coordinate value.

[0083] The slope reflects the inclination of the slope and is defined as the tangent value of the inclination angle of the slope. The slope is expressed in degrees and is numerically equal to the angle between the normal vector of the surface unit passing through a certain point and the z-axis. The schematic diagram is shown in Figure 3 The formula for extracting the slope is shown below:

[0084]

[0085] In the formula, f x is the rate of change of elevation in the x direction, f y is the rate of change of elevation in the y direction.

[0086] The slope direction is defined as follows: 0° is defined as the true north direction, and the angle between the clockwise direction and the true north direction represents the slope direction. The slope direction calculation formula is as follows:

[0087]

[0088] The slope obtained by the above formula has positive and negative angles with the x-axis, so it is necessary to calculate the slope according to f x and f y The positive or negative value of is further judged according to the following table:

[0089]

[0090]

[0091] The data source of the land cover type adopts FROM-GLC10, and the land cover type is remapped into water bodies, forest land, grassland, cultivated land and urban land.

[0092] The water area density is defined as the ratio of the water area within a certain radius around the tower to the total area, which is used to analyze the impact of water on lightning disasters. The calculation formula for water area density is: water area density = water area ÷ total area of ​​the region × 100%.

[0093] Step 4: Extract terrain factor parameters based on FME: Extract land cover type and ground inclination parameters based on FME.

[0094] The second implementation method: based on the tower point file and the ground cover type raster file and the coordinate system is the cgcs2000 geographic coordinate system, the ground cover type extraction step is calculated, including:

[0095] S11: Read the tower point xls, filter out the longitude outside China (according to China's geographical scope), add the serial number when reading, so as to restore the sorting when outputting the results, create point features according to the longitude and latitude, and perform projection transformation;

[0096] S12: Read the land cover type geotif data and project it;

[0097] S13: using the point feature and the raster overlay converter, obtaining the land use raster pixel value corresponding to the tower point, and passing the pixel value to the point feature as the land use classification code;

[0098] S14: Calculate the XY projection coordinate value of the tower and create text content output in txt format;

[0099] S15: Output the extraction result as txt text.

[0100] The third implementation method: based on the tower point file and the block elevation DEM file and the coordinate system is the cgcs2000 geographic coordinate system, the ground inclination angle extraction step is calculated, including:

[0101] 1) Read the tower point xls, filter out the longitude outside China (based on China's geographical scope), add a serial number when reading, to restore the order when outputting the results, create point features based on longitude and latitude, and perform projection transformation;

[0102] 2) The pole tower points are connected into power lines. When connecting, they are interrupted according to the group number attribute to prepare for calculating the direction of the power line and obtaining the vertical direction section of the pole tower; at the same time, the attributes are deleted and the power line number is added;

[0103] 3) Each power line is split into two segments with two nodes to facilitate the calculation of the direction of each power line segment, and numbers are added to the small segments, and the starting coordinates of the small segments are calculated as the starting point for subsequent rotation;

[0104] 4) Take the last small line segment and rotate it 180 degrees with the end point as the starting point to make it an extension of the last line segment;

[0105] 5) Rotate each small line segment 90 and 270 degrees to the left and mark left and right;

[0106] 6) The two small line segments on the left and right are respectively cut to 120, 90, 60, and 30 meters to obtain eight groups of cross-sectional projection line segments of different lengths perpendicular to the direction of travel of the power line;

[0107] 7) Arrange, number, calculate the length of the cross-section projection line segment group, split it into individual nodes, and add the cross-section line segment group number;

[0108] 8) Import dem, mosaic and merge, and project to 3-degree zoning;

[0109] 9) Use the point and grid overlay converter to obtain the node elevation, arrange the nodes in global order, make the tower point in front of the end point of the cross-section projection line, and obtain the elevation value of the previous element as the starting elevation of the current element;

[0110] 10) Delete redundant attributes, distinguish the tower point and the distal point according to the cross-section number value of the cross-section point, calculate the elevation difference according to the elevation value of the distal point and the elevation value of the tower point, and calculate the inclination value by inverse trigonometric function based on the cross-section length;

[0111] 11) Aggregate the cross-section point elements and merge the attributes by tower, and calculate the absolute average of the eight inclination angles. Then calculate the average values ​​for the left and right directions respectively, and then convert them into tower point elements;

[0112] 12) Use the read original tower point elements and the tower point elements with target attributes such as inclination angle restored according to the projection coordinate values ​​to search for the nearest elements, append the calculation results to the original tower point elements, and perform attribute sorting and element sorting operations;

[0113] 13) Output the calculation results as xls table.

[0114] Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art, and the model parameters of each electrical appliance are not specifically limited, and conventional equipment can be used.

[0115] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0116] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for extracting topography and landforms in a transmission line wind disaster assessment model, characterized in that: The following steps are involved: Step 1: Collect geographic data: collect terrain factor information, water system data, average wind direction data and soil data of the transmission line; Step 2: Data processing: transform the elevation data into WGS84 coordinates, and then project them into plane map coordinates; Step 3: Mathematical expression of terrain factors: Determine terrain type, altitude, slope, aspect, land cover type and water density in the plane map coordinate projection; Step 4: Extract terrain factor parameters based on FME: Extract land cover type and ground inclination parameters based on FME.

2. The method for extracting topography and landforms in a transmission line wind disaster assessment model according to claim 1, characterized in that: The terrain factor information includes: elevation, terrain type, slope, slope aspect, ground inclination, hillside, terrain relief, ridge line, valley line, surface cover type, water body density and water body distance; The elevation, terrain type, slope, aspect, ground inclination, hillside, terrain relief, ridge line and valley line are calculated using DEM data of the transmission line; The surface coverage type and water area density are calculated by superimposing the surface coverage type data of the transmission line and the longitude and latitude information of the tower; The water body distance is calculated by superimposing water system data on transmission line data.

3. The method for extracting topography and landforms in a transmission line wind disaster assessment model according to claim 1, characterized in that: The water system data adopts the terrain vector data disclosed by the National Tiantu Map, the average wind direction data is calculated using the free meteorological observation data released by the Meteorological Data Center of the China Meteorological Administration or the European Space Agency, and the soil data is obtained using the World Soil Database.

4. The method for extracting topography and landforms in a transmission line wind disaster assessment model according to claim 1, characterized in that: The plane map coordinate projection adopts Mercator projection. When the data of WGS84 coordinate system is converted into Mercator projection, the following simplified formula is used: Where x and y are the coordinates of the plane coordinate system after the projection is unfolded into a plane diagram, R is the radius of the standard sphere specified in WGS84, λ, is the angle parameter of WGS84 coordinate system; After the projection is completed, various types of terrain attribute information can be extracted and assigned.

5. The method for extracting topography and landforms in a transmission line wind disaster assessment model according to claim 1, characterized in that: The terrain type adopts the surface water physical simulation analysis method based on DEM, and divides the terrain into ridges, valleys, passes, windward slopes and leeward slopes, and flat land. According to the physical law of surface water, the cumulative runoff of the surface grid is calculated. The ridge is used as the watershed, and its cumulative runoff should be zero, so the watershed is obtained by connecting the points with zero cumulative runoff. The surface elevation data is inverted, and the watershed is divided in the same way to obtain the watershed under the positive terrain, that is, the valley. The pass is the intersection of the watershed and the watershed. The area except for the ridge, valley and pass terrain is the hillside area. The windward slope and leeward slope are extracted as follows: extract each hillside unit to be identified, calculate the slope direction of each hillside unit cyclically, search for the meteorological station closest to the grid unit position for each hillside unit to be divided, calculate the multi-year summer average wind direction of the meteorological station, compare the slope direction and summer wind direction, and divide the hillside unit with an angle between the slope direction and the wind direction within 90° into the windward slope, otherwise it is the leeward slope; The steepness at each pixel is read through the geographic information system, that is, the percentage of the elevation difference between two points and the horizontal distance, and the area with a steepness of 0-2% is defined as flat land.

6. The method for extracting topography and landforms in a transmission line wind disaster assessment model according to claim 1, characterized in that: The altitude is one of the basic information contained in the digital elevation data, and is approximately represented by the projected Z-axis coordinate value; The slope reflects the inclination of the slope and is defined as the tangent value of the inclination angle of the slope. The slope is expressed in degrees and is numerically equal to the angle between the normal vector of the surface unit passing through a certain point and the z-axis. The formula for extracting the slope is as follows: In the formula, f x is the rate of change of elevation in the x direction, f y is the rate of change of elevation in the y direction; The slope direction is defined as follows: 0° is defined as the true north direction, and the angle between the clockwise direction and the true north direction represents the slope direction. The slope direction calculation formula is as follows: The slope obtained by the above formula has positive and negative angles with the x-axis, so it is necessary to calculate the slope according to f x and f y Further judge the positive or negative; The data source of the land cover type adopts FROM-GLC10, and the land cover type is remapped into water bodies, forest land, grassland, cultivated land and urban land; The water area density is defined as the ratio of the water area within a certain radius around the tower to the total area, which is used to analyze the impact of water on lightning disasters. The calculation formula for water area density is: water area density = water area ÷ total area of ​​the region × 100%.

7. The method for extracting topography and landforms in a transmission line wind disaster assessment model according to claim 1, characterized in that: In the step 4, the calculation of the ground cover type extraction step is performed based on the tower point file and the ground cover type grid file and the coordinate system is the cgcs2000 geographic coordinate system, including: S11: Read the tower point xls, filter out the longitude outside China, add the serial number when reading, to restore the order when outputting the results, create point features according to the longitude and latitude, and perform projection transformation; S12: Read the land cover type geotif data and project it; S13: using the point feature and the raster overlay converter, obtaining the land use raster pixel value corresponding to the tower point, and passing the pixel value to the point feature as the land use classification code; S14: Calculate the XY projection coordinate value of the tower and create text content output in txt format; S15: Output the extraction result as txt text.

8. The method for extracting topography and landforms in a transmission line wind disaster assessment model according to claim 1, characterized in that: In the fourth step, the ground inclination angle extraction step is calculated based on the tower point file and the block elevation DEM file and the coordinate system is the cgcs2000 geographic coordinate system, including: 1) Read the tower point xls, filter out the longitude outside China, add the serial number when reading, and restore the order when outputting the results. Create point features according to the longitude and latitude, and perform projection transformation; 2) The pole tower points are connected into power lines. When connecting, they are interrupted according to the group number attribute to prepare for calculating the direction of the power line and obtaining the vertical direction section of the pole tower; at the same time, the attributes are deleted and the power line number is added; 3) Each power line is split into two segments with two nodes to facilitate the calculation of the direction of each power line segment, and numbers are added to the small segments, and the starting coordinates of the small segments are calculated as the starting point for subsequent rotation; 4) Take the last small line segment and rotate it 180 degrees with the end point as the starting point to make it an extension of the last line segment; 5) Rotate each small line segment 90 and 270 degrees to the left and mark left and right; 6) The two small line segments on the left and right are respectively cut to 120, 90, 60, and 30 meters to obtain eight groups of cross-sectional projection line segments of different lengths perpendicular to the direction of travel of the power line; 7) Arrange, number, calculate the length of the cross-section projection line segment group, split it into individual nodes, and add the cross-section line segment group number; 8) Import dem, mosaic and merge, and project to 3-degree zoning; 9) Use the point and grid overlay converter to obtain the node elevation, arrange the nodes in global order, make the tower point in front of the end point of the cross-section projection line, and obtain the elevation value of the previous element as the starting elevation of the current element; 10) Delete redundant attributes, distinguish the tower point and the distal point according to the cross-section number value of the cross-section point, calculate the elevation difference according to the elevation value of the distal point and the elevation value of the tower point, and calculate the inclination value by inverse trigonometric function based on the cross-section length; 11) Aggregate the cross-section point elements and merge the attributes by tower, and calculate the absolute average of the eight inclination angles. Then calculate the average values ​​for the left and right directions respectively, and then convert them into tower point elements; 12) Use the read original tower point element and the tower point element with inclination target attribute restored according to the projection coordinate value to search for the nearest element, and append the calculation result to the original tower point element; 13) Output the calculation results as xls table.

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