A large-scale and high-precision method for generating random lunar terrain

Abstract

The present invention provides a large-scale high-precision lunar random terrain generation method, which relates to the technical field of lunar terrain generation, and solves the problem that the quality of the existing digital terrain model is highly dependent on the accuracy of the original data source, and the low-precision remote sensing detection data or mapping data leads to errors in the model. The method includes the following steps: S1, according to the location information and range of the target area, based on the lunar surface DEM map, determine the regional terrain characteristics and impact crater type, and input the minimum diameter of stones and impact craters; S2, obtain the impact crater position and diameter in the lunar surface DEM map, split the target area terrain map, obtain multiple stone generation units, and generate a grid map, calculate the number of stones in each stone generation unit, and further calculate the number of stones in the target area; S3, generate terrain stones for the target area terrain map: S4, generate terrain impact craters for the target area terrain map: S5, calculate the elevation value in the target area, and generate a large-scale, high-precision lunar terrain.

Description

Technical Field

[0001] The present invention relates to the technical field of lunar terrain generation, and in particular to a large-scale and high-precision lunar random terrain generation method. Background Art

[0002] As human exploration of the moon deepens, the demand for high-precision maps of the lunar surface is increasing. The range of future manned lunar landings will be in the order of ten kilometers, and the accuracy of the maps will be high. Traditional high-precision lunar terrain generation is generally only 100m×100m in scale, and the base map is flat, which cannot meet the needs of manned lunar landing for terrain simulation. Therefore, a large-scale high-precision random map generation method for the lunar surface is urgently needed.

[0003] Digital terrain model refers to the use of digital representation to describe the spatial position and related attributes of the terrain surface. It is a reconstruction of the terrain surface based on terrain sampling data to simulate ground undulations. Establishing a large-scale high-precision map model of a certain area on the lunar surface can provide a more detailed working environment for manned lunar landing activities. Generating lunar surface terrain requires considering the impact terrain caused by the collision of foreign objects on the lunar surface, and it is necessary to determine the attribute parameters of obstacles such as rocks and impact craters. The attribute parameters include obstacle distribution attribute parameters and obstacle shape attribute parameters. The distribution attribute parameters are used to describe the location and number of obstacles in the generated area, while the shape attribute parameters are used to describe the size and shape of each specific obstacle. The organic connection of these attributes realizes the simulation of impact terrain. The generation of impact craters requires the establishment of different parameterized shape models according to different impact crater types such as fresh craters, young craters, mature craters and old craters. The quality of existing digital terrain models is highly dependent on the accuracy of the original data source. Low-precision remote sensing detection data or surveying and mapping data will cause errors in the model. Therefore, a method for obtaining higher-resolution data is urgently needed to obtain more detailed terrain information. Summary of the invention

[0004] The technical problems to be solved by the present invention are:

[0005] The quality of existing digital terrain models is highly dependent on the accuracy of the original data source. Low-precision remote sensing data or surveying and mapping data can lead to errors in the model.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] The present invention provides a large-scale and high-precision lunar random terrain generation method, which is characterized by comprising the following steps:

[0008] S1. According to the location information and range of the target area, determine the regional terrain characteristics and impact crater types based on the lunar surface DEM map, and input the minimum diameter of rocks and impact craters;

[0009] S2. Obtain the location and diameter of the impact crater in the lunar DEM map, split the topographic map of the target area, obtain multiple stone generation units, and generate a grid map, calculate the number of stones in each stone generation unit, and further calculate the number of stones in the target area;

[0010] S3. Generate terrain stones for the target area terrain map:

[0011] S3-1. Construct a stone distribution model according to different terrain features, and solve the model to calculate the stone number array corresponding to different stone diameter arrays;

[0012] S3-2, take the number array corresponding to the same stone diameter;

[0013] S3-3, based on the location and diameter of the impact crater in the lunar DEM map obtained in S2, the center point of the impact crater in the DEM map is taken as the center, and the center position of the stone is generated using normal distribution;

[0014] S3-4, searching the affected area of ​​the stone, calculating the elevation value in the affected area, and updating the elevation value of the stone in the target area;

[0015] S3-5, repeating steps S3-3 to S3-4 until the number of stones under the selected stone diameter in the stone generation unit is calculated;

[0016] S3-6, repeating steps S3-2 to S3-5 until the calculation of the stone diameter array in the stone generation unit is completed;

[0017] S4. Generate terrain impact craters for the target area topographic map:

[0018] S4-1. Construct a crater distribution model based on different terrain features, and solve the model to calculate the crater number array corresponding to different crater diameter arrays;

[0019] S4-2, take the number array corresponding to the diameter of the same impact crater;

[0020] S4-3, randomly generate the center position of the impact crater;

[0021] S4-4, searching the impact area of ​​the impact crater, calculating the elevation value in the impact area, and updating the elevation value in the target area;

[0022] S4-5, repeating steps S4-3 to S4-4 until the calculation of the number of impact craters under the impact crater diameter selected in the stone generation unit is completed;

[0023] S4-6, repeating steps S4-2 to S4-5 until the calculation of the impact crater diameter array in the stone generation unit is completed;

[0024] S5. Calculate and obtain the high energy elevation value in the target area.

[0025] Furthermore, the terrain features described in S1 include: flat lunar seas, rough lunar seas and lunar continents.

[0026] Furthermore, the impact crater types described in S1 include: fresh craters, young craters, mature craters and old craters.

[0027] Furthermore, obtaining the location and diameter of the impact crater in the lunar surface DEM map described in S2 includes the following process:

[0028] Calculate the curvature of each location point in the DEM map and get the curvature map:

[0029]

[0030] in, And n = m + 1, and are the first-order derivatives of elevation in the x and y directions, respectively. and are the second-order derivatives of elevation in the x and y directions respectively;

[0031] Perform binary image conversion on the curvature map to obtain a binary image;

[0032] The binary image is processed and then Hough transform is performed;

[0033] For the i-th object in the image after Hough transform, the pixel points on the edge of the crater must satisfy:

[0034] (1-ε) 2 r i 2 ≤(xx o,i ) 2 +(yy o,i ) 2 ≤(1+ε) 2 r i 2

[0035] In the above formula, x and y are the coordinates of the edge pixel points. o,i ,y o,i is the coordinate of the center of the crater, r i is the crater radius, ε is the control parameter;

[0036] The integrity of the edge of each potential impact crater C i Make a judgment and determine the roundness of the crater edge to determine whether the image to be tested contains the crater, and finally obtain the crater position and diameter.

[0037] Furthermore, the binary image is processed, including using a morphological closing operation to connect discontinuous areas, and then using a smoothing operator to perform a smoothing and thinning operation.

[0038] Furthermore, the stone distribution model described in S3-1 is specifically:

[0039] For the gentle lunar sea area:

[0040] lgN=-2.589×lgD-3.3955

[0041] For rough lunar mare areas:

[0042] lgN=-2.589×lgD-3.3955, D≤100;

[0043] lgN=-1.715×lgD-1.1905, 0.003 <D≤0.245;

[0044] lgN=-3.057×lgD-2.233, D>0.245

[0045] For the Lunar Land area:

[0046] lgN=-2.589×lgD-3.3955, D≤0.01;

[0047] lgN=-2.000×lgD-2.154, 0.01 <D≤0.763;

[0048] lgN=-3.015×lgD-2.625, D>0.763

[0049] Where N is the number of stones per square meter with a diameter greater than D, and D is the minimum stone diameter of interest;

[0050] Furthermore, S3-4 includes the following process:

[0051] The shape of the stone is modeled using a rotational parabola, specifically:

[0052] For the main simulation parameters of the stone: center point position coordinates, stone height and stone bottom radius, the parabola expression is:

[0053] R=(X-X0) 2 +(Y-Y0) 2

[0054] Z=HH×R / r 2

[0055] Where (X0, Y0) represents the position of the stone, H is the height of the stone, and r is the radius of the bottom of the stone;

[0056] Based on the different stone diameter arrays obtained in S3-1, randomly generate stone diameters evenly distributed within the diameter array range. Use the stone center position obtained in S3-3 to calculate the grid number affected by the stone in the map, and superimpose the stone elevation change on the elevation value of the base map.

[0057] Furthermore, the impact crater distribution model described in S4-1 is specifically:

[0058] For the gentle lunar sea area:

[0059] lgN'=-2×lgD'-1, D'≤40;

[0060] lgN'=-3×lgD'+0.602, D'>40

[0061] For rough lunar mare areas:

[0062] lgN'=-2×lgD'-1, D'≤100;

[0063] lgN'=-3×lgD'+1, D'>100

[0064] For the Lunar Land area:

[0065] lgN'=-2×lgD'-1, D'<1000;

[0066] lgN'=-3×lgD'+2,D'≥1000

[0067] where N' is the number of craters per square meter with a diameter greater than D', and D' is the smallest crater diameter of interest.

[0068] Furthermore, the randomly generated center positions of impact craters described in S4-3 are specifically: the center positions of impact craters of the same diameter range are randomly generated in the DEM map using a two-dimensional uniform distribution.

[0069] Further, S4-4 includes the following process:

[0070] A parameterized crater shape model is established according to the crater type, and the range of shape parameter changes of different types of craters is obtained by statistics. The shape of the crater is modeled using a piecewise rotation surface function model that combines a rotation parabola with a rotation arc surface, and the crater shape model is obtained:

[0071]

[0072] Among them, D dep represents the depth of the impact crater, D dia represents the diameter of the impact crater, D lipRepresents the pit lip height,

[0073] According to the obtained range of shape parameters of different types of impact craters, impact craters of different types, sizes and shapes are randomly generated;

[0074] Based on the different crater diameter arrays obtained in S4-1, the crater diameters are randomly generated uniformly within the diameter array range. The center position of the crater obtained in S4-3 is used to calculate the grid map number affected by the crater in the map, and the elevation change of the crater is superimposed on the elevation value of the base map.

[0075] Compared with the prior art, the present invention has the following beneficial effects:

[0076] The present invention determines the terrain type of the area and the distribution model of rocks and impact craters according to the lunar surface position and lunar surface terrain information of the target area. If the established lunar digital terrain library includes the large-scale terrain elevation information of the target area, the digital terrain library is extracted as the basic terrain information for subsequent terrain generation. Finally, according to the input stone and impact crater feature information, the center point position of the stone and impact crater is randomly generated, and the digital elevation information in the impact area is generated according to the stone and impact crater diameter. Therefore, the present invention can generate a large-scale and high-precision lunar surface topography map, providing more detailed and larger-scale environmental information for future manned lunar landing activities. The present invention uses the existing low-precision lunar surface DEM as the base map, emphasizes the authenticity of the distribution and size of lunar rocks and impact craters, and generates large-scale, high-fidelity, high-precision lunar surface terrain. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 This is a flow chart of a large-scale, high-precision lunar random terrain generation method in an embodiment of the present invention;

[0078] Figure 2 (a) is an impact crater identification map of a 30km×30km area around Bodrum Creek in an embodiment of the present invention, Figure 2 (b) is the binary image of the impact crater after binary conversion;

[0079] Figure 3 The distribution diagram of rocks between impact craters in the gentle lunar sea area, the rough lunar sea area and the lunar land area in the embodiment of the present invention;

[0080] Figure 4 The impact crater distribution map of the gentle lunar sea area, the rough lunar sea area and the lunar continent area in the embodiment of the present invention;

[0081] Figure 5 It is a schematic diagram of the oxz plane model of the impact crater shape in an embodiment of the present invention. DETAILED DESCRIPTION

[0082] In order to enable those skilled in the art to better understand the scheme of the present invention, exemplary implementations or embodiments of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described implementations or embodiments are only implementations or embodiments of a part of the present invention, not all of them. Based on the implementations or embodiments of the present invention, all other implementations or embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present invention.

[0083] Combination Figures 1 to 5 As shown, the present invention provides a large-scale and high-precision lunar random terrain generation method, comprising the following steps:

[0084] S1. According to the location information and range of the target area, the regional terrain features and impact crater types are determined based on the lunar surface DEM map. The terrain features include: flat lunar seas, rough lunar seas and lunar highlands. The impact crater types include: fresh craters, young craters, mature craters and old craters. According to the existing lunar surface data and actual application needs, the minimum diameter of the stone and the impact is fixed.

[0085] S2, obtaining the location and diameter of the impact crater in the lunar surface DEM map, splitting the topographic map of the target area to obtain multiple stone generation units, and generating a grid map, calculating the number of stones in each stone generation unit, and further calculating the number of stones in the target area; specifically including the following process:

[0086] Due to the low resolution of the DEM map, most of the impact craters are large ones with a diameter of more than 100m. Since the distribution of rocks on the lunar surface has obvious regularity, that is, most of the rocks are scattered around large impact craters, in order to ensure the authenticity of the high-precision map, it is necessary to identify and read the location and diameter of large impact craters in the base map. Obtaining the location and diameter of impact craters in the lunar DEM map includes the following process:

[0087] The terrain curvature is used to reflect the edge characteristics of the impact crater, so as to determine the location and diameter of the impact crater. The curvature of each location point in the DEM map is calculated to obtain the curvature map:

[0088]

[0089] in, And n = m + 1, and are the first-order derivatives of elevation in the x and y directions, respectively. and are the second-order derivatives of elevation in the x and y directions, respectively; it is usually assumed that elevation and its derivatives are continuous and differentiable in both the x and y directions. Since more noise will be introduced when the terrain is directly differentiated, the DEM is first smoothed when calculating the terrain curvature.

[0090] According to empirical data, the curvature map is converted into a binary image to obtain a binary image:

[0091]

[0092] The impact crater identification map of the 30km×30km area around Bodrum Creek is as follows Figure 2 As shown in (a), the converted binary image is Figure 2 (b) As shown in the figure, all the craters with larger diameters can be identified, but the edges are notched. In addition, there are many misjudgments, mainly concentrated in the area with higher elevation values ​​on the right side of the map, where many light-colored areas that cannot be closed appear.

[0093] A morphological closing operation is used to connect discontinuous regions, and then a 3×3 smoothing operator is used for smoothing and thinning operations, followed by a Hough transform to reduce the number of candidate craters.

[0094] For the i-th object in the image after Hough transform, the pixel points on the edge of the crater need to satisfy:

[0095] (1-ε) 2 r i 2 ≤(xx o,i ) 2 +(yy o,i ) 2 ≤(1+ε) 2 r i 2

[0096] In the above formula, x and y are the coordinates of the edge pixel points. o,i ,y o,i is the coordinate of the center of the crater, r i is the radius of the crater, and ε is the control parameter; that is, all edge pixels should be within a (1-ε) 2 r i 2 to (1+ε) 2 r i 2 In addition, since the edge pixels may be discontinuous, it is necessary to determine their integrity, that is, to count the total number of pixels in the ring and calculate the integrity C of the edge of each pending crater. iMake a judgment and determine the roundness of the crater edge:

[0097] R i =4πS / P 2

[0098] Where S is the area of ​​the pixel at the edge of the crater; P is the perimeter of the edge of the crater. The roundness R of craters of different sizes is determined by i Finally, the judgment threshold is set according to the empirical value to determine whether the image to be tested contains an impact crater. Finally, the position and diameter of the impact crater are obtained.

[0099] When generating high-precision large-scale maps, it is necessary to limit the upper limit of the diameter of rocks and impact craters. To this end, the large-scale topographic map of the target area is split to obtain multiple stone generation units, and the number and diameter of rocks and impact craters are calculated respectively to limit the diameter of rocks and impact craters. The size of rocks on the moon generally does not exceed 100mm. Based on this, the size of the stone generation unit should be 10m×10m. Calculate the number of rocks in each stone generation unit and obtain the number of rocks in the entire map of the target area = the number of rocks in the unit × the number of units. The upper limit of the diameter of the impact crater is equal to the resolution of the base map, and there is no need to split the map.

[0100] S3. Generate terrain stones for the target area terrain map:

[0101] S3-1. Construct a stone distribution model according to different terrain features, and solve the model to calculate the stone number array corresponding to different stone diameter arrays.

[0102] The distribution of rocks in the flat lunar sea area, rough lunar sea area and lunar continent area is as follows Figure 3 As shown. Figure 3 The mathematical model of rock distribution can be obtained by fitting. Given the terrain characteristics of the landing area (gentle lunar sea area, rough lunar sea area and lunar land area) and the minimum rock diameter D of interest, the corresponding formula is selected to calculate the number of rocks N per square meter with a diameter greater than D.

[0103] The stone distribution model is specifically:

[0104] For the gentle lunar sea area:

[0105] lgN=-2.589×lgD-3.3955

[0106] For rough lunar mare areas:

[0107] lgN=-2.589×lgD-3.3955, D≤100;

[0108] lgN=-1.715×lgD-1.1905, 0.003 <D≤0.245;

[0109] lgN=-3.057×lgD-2.233, D>0.245

[0110] For the Lunar Land area:

[0111] lgN=-2.589×lgD-3.3955, D≤0.01;

[0112] lgN=-2.000×lgD-2.154, 0.01 <D≤0.763;

[0113] lgN=-3.015×lgD-2.625, D>0.763

[0114] Where N is the number of stones per square meter with a diameter greater than D, and D is the smallest stone diameter of interest.

[0115] Taking the calculation of the number of rocks N with diameters in the range [D1, D2] in the gentle lunar sea area as an example, it is necessary to calculate the number of rocks with diameters greater than D1 and D2 respectively according to the rock distribution model describing the gentle lunar sea area. and The difference between the two, N1-N2, is the number of rocks N in the flat lunar sea area with a diameter in the range [D1, D2]. i ,D i+1 ] to calculate the number of stones obtained. i} is the array of the number of stones.

[0116] The diameter interval of the stone is divided into two parts, the lower limit of the diameter is the minimum value and the upper limit of the diameter is the maximum value. When dividing the interval, the applicable range of the calculation formula needs to be considered. The diameter interval selects the corresponding fixed value according to the characteristics of the interval.

[0117] S3-2, take the number array corresponding to the same stone diameter;

[0118] S3-3, based on the location and diameter of the impact crater in the lunar DEM map obtained in S2, take the center point of the impact crater in the DEM map as the center, and use a two-dimensional normal distribution to randomly generate the center position of stones with a diameter range outside the impact crater;

[0119] S3-4, searching the affected area of ​​the stone, calculating the elevation value in the affected area, and updating the elevation value of the stone in the target area; including the following process:

[0120] The shape of the stone is modeled using a rotational parabola, specifically:

[0121] For the main simulation parameters of the stone: center point position coordinates, stone height and stone bottom radius, the parabola expression is:

[0122] R=(X-X0) 2 +(Y-Y0) 2

[0123] Z=HH×R / r 2

[0124] Where (X0, Y0) represents the position of the stone, H is the height of the stone, and r is the radius of the bottom of the stone.

[0125] Based on the different stone diameter arrays obtained in S3-1, for stones with diameters in the range [D1, D2], randomly generate stone diameters uniformly distributed within the diameter array [D1, D2]. Use the stone center position (X0, Y0) obtained in S3-3 to calculate the grid number affected by the stone in the map, and superimpose the stone's elevation change Z on the elevation value of the base map.

[0126] S3-5, repeating steps S3-3 to S3-4 until the calculation of the number of stones under the stone diameter selected in the stone generation unit is completed.

[0127] S3-6. Repeat steps S3-2 to S3-5 until the calculation of the stone diameter array in the stone generation unit is completed.

[0128] S4. Generate terrain impact craters for the target area topographic map:

[0129] S4-1. Construct a crater distribution model based on different terrain features, and solve the model to calculate the crater number array corresponding to different crater diameter arrays.

[0130] From the detection data of lunar topography, it can be known that rocks and impact craters are the main features of lunar topography. By simulating the number and distribution of rocks and impact craters in the area, digital elevation information of the area can be obtained to describe its topography.

[0131] The distribution of impact craters in the gentle lunar sea area, rough lunar sea area and lunar continent area is as follows Figure 4 As shown. Figure 4 The distribution model of impact craters can be obtained from:

[0132] For the gentle lunar sea area:

[0133] lgN'=-2×lgD'-1, D'≤40;

[0134] lgN'=-3×lgD'+0.602, D'>40

[0135] For rough lunar mare areas:

[0136] lgN'=-2×lgD'-1, D'≤100;

[0137] lgN'=-3×lgD'+1, D'>100

[0138] For the Lunar Land area:

[0139] lgN'=-2×lgD'-1, D'<1000;

[0140] lgN'=-3×lgD'+2,D'≥1000

[0141] where N' is the number of craters per square meter with a diameter greater than D', and D' is the smallest crater diameter of interest.

[0142] Taking the calculation of the number of impact craters N' in the gentle lunar sea area with a diameter in the range [D1', D2'] (D2' < 40m) as an example, according to the distribution model describing the impact craters in the gentle lunar sea area, the number of impact craters with diameters greater than D1' and D2' is calculated respectively. and The difference between the two, N1'-N2', is the number of impact craters N' in the flat lunar sea region with diameters in the range [D1', D2']. i ',D i+1 '] to calculate the number of impact craters obtained. i '} is the array of impact crater numbers.

[0143] The diameter interval of the impact crater is divided into two parts, the lower limit of the diameter is the minimum value and the upper limit of the diameter is the maximum value. When dividing the interval, the applicable range of the calculation formula needs to be considered. The diameter interval selects the corresponding fixed value according to the characteristics of the interval.

[0144] S4-2, take the number array corresponding to the diameter of the same impact crater;

[0145] S4-3, using two-dimensional uniform distribution to randomly generate the center positions of impact craters in the same diameter range in the DEM map;

[0146] S4-4, searching the impact area of ​​the impact crater, calculating the elevation value in the impact area, and updating the elevation value in the target area; including the following process:

[0147] The shapes of impact craters distributed on the lunar surface vary greatly, making it difficult to describe them uniformly. At the same time, as obstacles in the path planning process, impact craters do not require an exact description of their shapes. A parameterized impact crater shape model is established based on the impact crater type, and the range of shape parameters of different types of impact craters is statistically obtained, as shown in Table 1.

[0148] Table 1

[0149] Pit Type Fresh pit Young pit Mature pit parameter <![CDATA[D dep. / D dia ]]> 0.23-0.25 0.17-0.19 0.11-0.13 scope <![CDATA[D lip / D dia ]]> 0.022-0.06 0.016-0.045 0.008-0.03

[0150] The shape of the impact crater is modeled by a piecewise rotation surface function model that combines a rotation parabola with a rotation arc surface. In this way, different types and sizes of impact craters can be achieved by adjusting the function parameters, such as Figure 5 The figure shows the model schematic diagram projected on the oxz plane. On the oxz plane, the parabola passes through the coordinate point (0,D lip -D dep ) and coordinate points (±D dia / 2,D lip ), the rotating arc surface passes through the coordinate point (±D dia / 2,D lip ), from which the equations of the rotating parabola and the rotating arc surface can be determined, and then the shape model of the impact crater can be obtained:

[0151]

[0152] Among them, D dep represents the depth of the impact crater, D dia represents the diameter of the impact crater, D lip Represents the pit lip height, D R Represents the radius of the arc of rotation, D R is an intermediate variable.

[0153] According to the variation range of shape parameters of different types of impact craters obtained in Table 1, impact craters of different types, sizes and shapes are randomly generated.

[0154] Based on the different crater diameter arrays obtained in S4-1, for craters with diameters in the range [D1, D2], the crater diameters are randomly generated uniformly distributed within the diameter array range [D1, D2]. The center position of the crater obtained in S4-3 is used to calculate the grid map number divided in S2 in the map affected by the crater, and the elevation change of the crater is superimposed on the elevation value of the base map.

[0155] S4-5, repeating steps S4-3 to S4-4 until the calculation of the number of impact craters under the impact crater diameter selected in the stone generation unit is completed.

[0156] S4-6. Repeat steps S4-2 to S4-5 until the calculation of the impact crater diameter array in the stone generation unit is completed.

[0157] S5. Calculate and obtain the high energy elevation value in the target area.

[0158] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A large-scale and high-precision lunar random terrain generation method, characterized in that: The steps include: S1. According to the location information and range of the target area, determine the regional terrain characteristics and impact crater types based on the lunar surface DEM map, and input the minimum diameter of rocks and impact craters; S2. Obtain the location and diameter of the impact crater in the lunar DEM map, split the topographic map of the target area, obtain multiple stone generation units, and generate a grid map, calculate the number of stones in each stone generation unit, and further calculate the number of stones in the target area; S3. Generate terrain stones for the target area terrain map: S3-1. Construct a stone distribution model according to different terrain features, and solve the model to calculate the stone number array corresponding to the stone diameter array; S3-2, take the number of stones corresponding to the diameter of one stone; S3-3, based on the location and diameter of the impact crater in the lunar DEM map obtained in S2, the center point of the impact crater in the DEM map is taken as the center, and the center position of the stone is generated using normal distribution; S3-4, searching the affected area of ​​the stone, calculating the elevation value in the affected area, and updating the elevation value of the stone in the target area; S3-5, repeating steps S3-3 to S3-4 until the calculation of the stones under the selected stone diameter in the stone generation unit is completed; S3-6, repeating steps S3-2 to S3-5 until the calculation of stones with all stone diameters in the stone generation unit is completed; S4. Generate terrain impact craters for the target area topographic map: S4-1. Construct a crater distribution model based on different terrain features, and solve the model to calculate the crater number array corresponding to the crater diameter array; S4-2, take the number of craters corresponding to the diameter of a crater; S4-3, randomly generate the center position of the impact crater; S4-4, searching the impact area of ​​the impact crater, calculating the elevation value in the impact area, and updating the elevation value in the target area; S4-5, repeating steps S4-3 to S4-4 until the calculation of the impact crater under the impact crater diameter selected in the target area is completed; S4-6, repeating steps S4-2 to S4-5 until the calculation of all craters under the crater diameter in the target area is completed; S5. Calculate and obtain the elevation value in the target area.

2. The large-scale and high-precision lunar random terrain generation method according to claim 1 is characterized in that: The terrain features described in S1 include: flat lunar seas, rough lunar seas and lunar continents.

3. The large-scale and high-precision lunar random terrain generation method according to claim 2 is characterized in that: The types of impact craters described in S1 include: fresh craters, young craters, mature craters and old craters.

4. The large-scale and high-precision lunar random terrain generation method according to claim 1 is characterized in that: The process of obtaining the location and diameter of impact craters in the lunar DEM map described in S2 includes the following steps: Calculate the curvature of each location point in the DEM map and get the curvature map: in, And n = m + 1, and are the first-order derivatives of elevation in the x and y directions, respectively. and are the second-order derivatives of elevation in the x and y directions respectively; Perform binary image conversion on the curvature map to obtain a binary image; The binary image is processed and then Hough transform is performed; For the i-th object in the image after Hough transform, the pixel points on the edge of the crater must satisfy: (1-e) 2 r i 2 ≤(xx o,i ) 2 +(yy o,i ) 2 ≤(1+ε) 2 r i 2 In the above formula, x and y are the coordinates of the edge pixel points. o,i ,y o,i is the coordinate of the center of the crater, r i is the crater radius, ε is the control parameter; The integrity of the edge of each potential impact crater C i Make a judgment and determine the roundness of the crater edge to determine whether the image to be tested contains the crater, and finally obtain the crater position and diameter.

5. The large-scale and high-precision lunar random terrain generation method according to claim 4 is characterized in that: The binary image is processed by using a morphological closing operation to connect discontinuous areas, and then using a smoothing operator to perform a smoothing and thinning operation.

6. The large-scale and high-precision lunar random terrain generation method according to claim 1 is characterized in that: The stone distribution model described in S3-1 is specifically: For the gentle lunar sea area: lg N=-2.589×lg D-3.3955 For rough lunar mare areas: lg N=-2.589×lg D-3.3955, D≤100; lg N=-1.715×lg D-1.1905, 0.003<D≤0.245; lg N=-3.057×lg D-2.233, D>0.245 For the Lunar Land area: lg N=-2.589×lg D-3.3955, D≤0.01; lg N=-2.000×lg D-2.154, 0.01<D≤0.763; lg N=-3.015×lg D-2.625, D>0.763 Where N is the number of stones per square meter with a diameter greater than D, and D is the smallest stone diameter of interest.

7. The large-scale and high-precision lunar random terrain generation method according to claim 1 is characterized in that: S3-4 includes the following processes: The shape of the stone is modeled using a rotational parabola, specifically: For the main simulation parameters of the stone: center point position coordinates, stone height and stone bottom radius, the parabola expression is: R=(X-X0) 2 +(Y-Y0) 2 Z=H-H×R / r 2 Where (X0, Y0) represents the position of the stone, H is the height of the stone, and r is the radius of the bottom of the stone; Based on the different stone diameter arrays obtained in S3-1, randomly generate stone diameters evenly distributed within the diameter array range. Use the stone center position obtained in S3-3 to calculate the grid number affected by the stone in the map, and superimpose the stone elevation change on the elevation value of the base map.

8. The large-scale and high-precision lunar random terrain generation method according to claim 1 is characterized in that: The impact crater distribution model described in S4-1 is specifically: For the gentle lunar sea area: lg N'=-2×lg D'-1, D'≤40; lg N'=-3×lg D'+0.602, D'>40 For rough lunar mare areas: lg N'=-2×lg D'-1, D'≤100; lg N'=-3×lg D'+1, D'>100 For the Lunar Land area: lg N'=-2×lg D'-1, D'<1000; lg N'=-3×lg D'+2,D'≥1000 where N' is the number of craters per square meter with a diameter greater than D', and D' is the smallest crater diameter of interest.

9. The large-scale and high-precision lunar random terrain generation method according to claim 1 is characterized in that: The randomly generated center positions of impact craters described in S4-3 are specifically: the center positions of impact craters with the same diameter range are randomly generated in the DEM map using a two-dimensional uniform distribution.

10. The large-scale and high-precision lunar random terrain generation method according to claim 1 is characterized in that: S4-4 includes the following process: A parameterized crater shape model is established according to the crater type, and the range of shape parameter changes of different types of craters is obtained by statistics. The shape of the crater is modeled using a piecewise rotation surface function model that combines a rotation parabola with a rotation arc surface, and the crater shape model is obtained: Among them, D dep represents the depth of the impact crater, D dia represents the diameter of the impact crater, D lip Represents the pit lip height, According to the obtained range of variation of shape parameters of different types of craters, craters of different types, sizes and shapes are randomly generated; based on the different crater diameter arrays obtained in S4-1, the crater diameters are randomly generated in a uniform distribution within the diameter array range, and the center position of the crater obtained in S4-3 is used to calculate the grid map number affected by the crater in the map, and the elevation change of the crater is superimposed on the elevation value of the base map.

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