A vector polygon rasterization method of a spherical hexagonal grid system

Abstract

The application relates to a vector polygon rasterization method of a spherical hexagonal grid system and belongs to the technical field of geographic information. The vector polygon area to be rasterized is rasterized from coarse resolution to fine resolution by using the hierarchical characteristics of the grid system and adopting a cross-layer subdivision mode. The subdivision mode can generate a subunit by spacing a plurality of grid levels of a parent unit, solves the position uncertainty problem of the subunit relative to the parent unit after multiple times of subdivision of an adjacent level subdivision scheme, greatly reduces the number of units needing spatial relation judgment with the vector polygon, avoids the rasterization realized by traversing and judging the spatial relation of units one by one, and greatly improves the efficiency of the vector polygon rasterization on the spherical hexagonal grid system.

Description

Technical Field

[0001] This invention relates to a vector polygon rasterization method for a spherical hexagonal grid system, belonging to the field of geographic information technology. Background Technology

[0002] Vector and raster are two of the most basic spatial data representation forms in Geographic Information Systems (GIS), and these two types of data often need to be converted to each other. With the development of computer display technology, the rasterization of vector data, especially vector polygon data, has gradually become one of the important research issues in the field of GIS. With the development of sensor technology, the scale of geospatial data available to humans has grown rapidly, and the increasing complexity of data has made traditional GIS data organization and processing models increasingly unable to meet the needs. The Discrete Global Grid System (DGGS) is an emerging type of Earth reference frame that recursively discretizes Earth's space into a set of regular cells with different resolutions. Each grid cell corresponds one-to-one with a surface region and is assigned a unique identifier. It has excellent characteristics such as global coverage, multi-scale operation, and computational efficiency, creating excellent conditions for the organization, processing, and analysis of geospatial data.

[0003] Vector data is discretized into a series of grid cells in a grid system, which is essentially similar to vector rasterization algorithms. Obtaining grid cells covering the vector polygon region is also a prerequisite and foundation for region analysis in DGGS, thus having significant research and application value. Since traditional vector rasterization algorithms generally target rectangular pixels arranged in a regular planar pattern, while DGGS studies the Earth's surface and, based on cell shape, categorizes DGGS into three types: triangular, quadrilateral, and hexagonal, it is necessary to research vector polygon rasterization methods suitable for DGGS.

[0004] In the three types of spherical grid systems, the hierarchical subdivisions of triangles and quadrilaterals exhibit overlap, making it easy to leverage the multi-scale characteristics and efficient indexing operations of DGGS to improve the gridding efficiency of polygonal regions. However, the hierarchical subdivisions of hexagons lack overlap, meaning that a large hexagon cannot be subdivided into several smaller hexagons. The hierarchical relationships between units are unclear, and there is always a contradiction between the logical attribution relationship between parent and child units and the actual surface cover area, increasing the difficulty and complexity of designing hexagonal DGGS algorithms.

[0005] Current vector polygon region rasterization algorithms for spherical hexagonal grid systems, such as the open-source models DGGRID and H3, mostly adopt a single-resolution traversal approach, judging the spatial relationship between grid cells and regions one by one. Although they can accurately generate the target cell set, the polygon spatial relationship judgment function is time-consuming. In practical applications, as the research area expands and the resolution increases, the number of grid cells will increase dramatically, resulting in very low algorithm efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a vector polygon rasterization method for a spherical hexagonal grid system, so as to solve the problem of low efficiency caused by the current single-resolution traversal approach for rasterization of spherical hexagonal grid systems.

[0007] To solve the above-mentioned technical problems, this invention provides a vector polygon rasterization method for a spherical hexagonal grid system, the method comprising the following steps:

[0008] 1) Obtain the vector polygon region to be rasterized and the target resolution level of rasterization. Determine a coarse resolution level based on the vector polygon region and the target resolution level of rasterization. Perform spherical hexagonal rasterization on the vector polygon region based on the coarse resolution level to obtain coarse resolution grid cells as initial cells.

[0009] 2) The internal initial unit is directly partitioned to the target resolution level using cross-layer partitioning mode B; the cross-layer partitioning mode B refers to the parent unit generating two types of sub-units, internal and edge, at intervals of multiple grid levels, retaining all internal sub-units and retaining some edge sub-units.

[0010] 3) The initial boundary unit is partitioned using cross-layer partitioning mode A to obtain the internal sub-units of each intermediate resolution level, the external sub-units of each intermediate resolution level, and the m-2 layer boundary sub-units closest to the target resolution level, where m is the target resolution level; the cross-layer partitioning mode A refers to the generation of internal and edge sub-units by the parent unit at intervals of multiple grid levels, while retaining all internal and edge sub-units.

[0011] 4) Using cross-layer partitioning mode B, the internal sub-units of each intermediate resolution level and the external sub-units of each intermediate resolution level are directly partitioned to the target resolution level;

[0012] 5) Use cross-layer partitioning mode B to partition the m-2 layer boundary sub-units closest to the target resolution level to the target resolution level;

[0013] 6) Convert the coordinate system of each target resolution sub-unit to the DGGS unit address or geographic coordinates. The result after conversion is the vector polygon rasterization result.

[0014] This invention employs a cross-layer partitioning method to rasterize the vector polygon region to be rasterized. This partitioning method can generate sub-units by separating the parent unit from multiple grid layers, solving the problem of uncertainty in the position of the sub-unit relative to the parent unit after multiple partitioning schemes of adjacent layers. This greatly reduces the number of units that need to be judged in terms of spatial relationship with the vector polygon, avoids traversing each unit one by one to judge the spatial relationship with the vector polygon, and greatly improves the efficiency of vector polygon rasterization of the spherical hexagonal grid system.

[0015] Furthermore, in the cross-layer partitioning mode B, when retaining some edge sub-units, the center of the four-hole partitioning is located on one of the three edges of the parent unit, and the center of the three-hole partitioning is located on one of the two edges of the parent unit.

[0016] The cross-layer partitioning mode B of the present invention can ensure the uniqueness of the generation of all sub-units at the same level by handling the deletion of edge sub-units.

[0017] Furthermore, in step 3), the initial boundary unit subdivision is performed recursively, with subdivision occurring at consecutive even-numbered layers. The process is as follows:

[0018] a. The initial boundary unit of level n is partitioned into n+2 levels using cross-level partitioning mode A, resulting in n+2 sub-units. The n+2 sub-units include n+2 internal sub-units within the vector polygon region, n+2 external sub-units outside the vector polygon region, and n+2 boundary sub-units intersecting with the vector polygon region.

[0019] b. Determine whether n+4 satisfies the condition of being less than or equal to m-4 or less than m-2. If it does, divide the n+2 layer boundary sub-units into the n+4 layer using the cross-layer partitioning mode A, resulting in the n+4 layer internal sub-units, n+4 layer external sub-units, and n+4 layer boundary sub-units.

[0020] c. Repeat step b until n+2k is greater than m-4 to obtain the internal sub-units of each intermediate resolution level, the external sub-units of each intermediate resolution level, and the boundary sub-units of the m-2 level.

[0021] This invention utilizes a partitioning mode A with complete sub-units, continuously partitioning the initial boundary units at even-number intervals, thus ensuring the integrity of the rasterized units. The initial boundary units are partitioned using a hierarchical recursive method to obtain internal sub-units of each intermediate resolution level, external sub-units of each intermediate resolution level, and the final boundary sub-units. Furthermore, in step 4), when directly partitioning the external sub-units of the intermediate resolution level to the target resolution level, only the partitioned boundary sub-units are retained.

[0022] Since the external sub-units at each level are directly decomposed to the target resolution level, only the edge sub-units may be related to the vector polygon. Therefore, in order to improve the processing efficiency in one step, this invention only retains the boundary sub-units after decomposition.

[0023] Furthermore, it also includes a step of checking the uniqueness of the sub-units obtained from step 4) for the target resolution level. If the uniqueness check condition of the sub-unit is not met, the sub-unit is deleted. The uniqueness check condition of the sub-unit is: the sub-unit must be located in the target resolution level sub-unit set generated by all its boundary parent units at the same time.

[0024] This invention utilizes the uniqueness check condition of sub-units to perform uniqueness checks on sub-units directly subdivided from external sub-units to the target resolution level, solving the problem of sub-unit overlap caused by the non-overlapping of hexagonal unit levels. It ensures that after the vector polygon is rasterized, each grid unit is generated only once, and there is no overlap between units. Moreover, this uniqueness check can be achieved through integer coordinate calculations.

[0025] Furthermore, it also includes judging the sub-units of the external units of the intermediate resolution level in step 4) after uniqueness check, judging whether each sub-unit overlaps with the polygon vector region. If there is no overlap, the sub-unit is directly deleted, and only the sub-units that overlap are retained.

[0026] Furthermore, in step 5), when partitioning to the target resolution level using cross-layer partitioning mode B, all sub-units are retained.

[0027] Furthermore, step 5) also includes a step of checking the uniqueness of the sub-units obtained from step 4) for the target resolution level. If the uniqueness check condition of the sub-unit is not met, the sub-unit is deleted. The uniqueness check condition of the sub-unit is: the sub-unit must be located in the target resolution level sub-unit set generated by all its boundary parent units at the same time.

[0028] Furthermore, step 5) also includes judging the sub-units that have undergone uniqueness checks, judging whether each sub-unit overlaps with the polygon vector region. If there is no overlap, the sub-unit is directly deleted, and only the sub-units that overlap are retained.

[0029] This invention utilizes the uniqueness check condition of sub-units to perform uniqueness checks on sub-units directly subdivided from external sub-units to the target resolution level, solving the problem of sub-unit overlap caused by the non-overlapping of hexagonal unit levels, and ensuring that after the vector polygon is rasterized, each grid unit is generated only once, and there is no overlap between units. Attached Figure Description

[0030] Figure 1This is a schematic diagram of vector polygon rasterization on the spherical hexagonal grid system used in the embodiments of the present invention;

[0031] Figure 2a This is a schematic diagram of the four-hole hexagonal grid cross-layer partitioning mode A with two layers spanned, which is adopted in this invention.

[0032] Figure 2b This is a schematic diagram of the four-hole hexagonal grid cross-layer partitioning mode B with two layers spanned, which is adopted in this invention.

[0033] Figure 3a This is a schematic diagram of the cross-layer partitioning mode A of the four-hole hexagonal grid with a span of 2 layers adopted in this invention in the local integer coordinate system;

[0034] Figure 3b This is a schematic diagram of the cross-layer partitioning mode B of the four-hole hexagonal grid with a span of 2 layers adopted in this invention in the local integer coordinate system;

[0035] Figure 4 This is a flowchart of vector polygon rasterization on the spherical hexagonal grid system of the present invention;

[0036] Figure 5 This is a schematic diagram of the grid partitioning hierarchy based on even-numbered layer partitioning in this invention;

[0037] Figure 6 This is a schematic diagram of the initial coarse resolution unit generated by the present invention;

[0038] Figure 7 This is a schematic diagram of the internal initial unit subdivided to the target resolution in an embodiment of the present invention;

[0039] Figure 8 This is a schematic diagram of a recursive subdivision of a boundary initial unit in an embodiment of the present invention;

[0040] Figure 9 This is a schematic diagram of the recursive subdivision of a certain boundary initial unit in an embodiment of the present invention;

[0041] Figure 10 This is a schematic diagram illustrating the uniqueness check of the target resolution hierarchical unit in an embodiment of the present invention;

[0042] Figure 11 This is a schematic diagram of the external subunit breakdown in an embodiment of the present invention;

[0043] Figure 12 This is a schematic diagram of grid quantization of DEM data after polygon rasterization in an embodiment of the present invention. Detailed Implementation

[0044] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0045] This invention utilizes the multi-scale characteristics of a grid system and a hexagonal unit hierarchical structure to iteratively subdivide coarse-resolution grid units covering vector polygon regions to target-resolution grid units using a cross-layer recursive method, achieving rasterization of vector polygons on a spherical hexagonal grid system. The cross-layer subdivision scheme refers to generating sub-units from a parent unit across multiple grid layers, using these sub-units as the basis for grid hierarchical subdivision. After cross-layer subdivision, the parent unit generates only two types of sub-units: internal and edge sub-units. Internal sub-units are centered within the parent unit and their covered area completely belongs to the parent unit, while edge sub-units are centered on the parent unit boundary and their partially covered area does not overlap with the parent unit. This partitioning method avoids traversing each unit individually to determine its spatial relationship with the vector polygons, and then utilizes the grid system's efficient integer-encoded hierarchical index to generate most grid units, thereby significantly improving rasterization efficiency.

[0046] By assigning ownership of edge sub-units, this invention designs two cross-layer partitioning modes for different scenarios of unit partitioning during vector polygon rasterization.

[0047] Partitioning Mode A: Retains all internal and edge sub-units, ensuring the integrity of the sub-unit coverage area.

[0048] Figure 2a The sub-cells generated by partitioning a four-hole hexagonal grid using mode A with an interval of 2 layers include 13 white-filled internal sub-cells and 6 edge sub-cells centered on the 6 edges of the parent cell. If partitioned to an even number of layers (4, 6, etc.), the sub-cells still have a similar arrangement rule, and there are no sub-cells located outside the parent cell.

[0049] Establishing an integer coordinate system on the parent cell can describe the positional patterns of its child cells. Taking a four-hole hexagonal grid divided into even-numbered layers as an example, a local two-dimensional integer coordinate system can be established on any hexagonal cell in the nth layer of the grid to describe the positional patterns of that cell and its child cells. + The positional relationship of the sub-units in the nth layer: taking the vertex of the parent unit of the nth layer as the origin, the two adjacent sides as the I-axis and J-axis, and (i, j) as the coordinates of the unit center, then n+2k (k∈N) + ) Layer sub-unit center set It can be represented as:

[0050]

[0051] Where 0≤i, j≤2 2k+1 The values ​​of the I-axis and J-axis in this local coordinate system are defined by %; % represents the modulo operation, (i+j)%3=2 indicates that the point is the center of the hexagonal element, and the rest are the coordinates of the vertices of the hexagonal elements; (ji)≤4 k , (ij)≤4 kThis represents a child cell that is related to the parent cell region. Figure 3a This example illustrates a local integer coordinate system constructed by an n-layer parent cell in a four-hole hexagonal grid at layer n+2. In this embodiment, the side length of the hexagonal sub-cell at layer n+2 is defined as unit 1.

[0052] Partitioning Mode B: Retains all internal sub-units. For edge sub-units, a four-hole hexagonal partition is used, where the area of ​​the parent unit in the adjacent level is 4 times that of the sub-unit. Edge sub-units whose center is located on one of the three edges of the parent unit are retained. A three-hole hexagonal partition is used, where the area of ​​the parent unit in the adjacent level is 3 times that of the sub-unit. Edge sub-units whose center is located on one of the two edges of the parent unit are retained. This partitioning mode can guarantee the uniqueness of all sub-units generated at the same level.

[0053] like Figure 2b As shown, the hexagonal grid is divided into two layers using a cross-layer partitioning pattern B. It includes 13 internal sub-cells filled in white and sub-cells centered on one of the three edges of the parent cell. (See diagram.) Figure 3b As shown, if we select a local coordinate system located at the I-axis, J-axis, and ji = 4... k The boundary sub-units on the three sides, then any unit in the nth layer is partitioned to n+2k (k∈N) + The unique sub-unit center set of the layer Represented as:

[0054]

[0055] Based on the above cross-layer partitioning scheme, the process of rasterizing vector polygon data on a spherical hexagonal grid system is as follows: Figure 4 As shown, the hierarchical changes during the partitioning process are as follows: Figure 5 As shown below, specific examples will be used to explain the process in detail.

[0056] 1. Perform hexagonal meshing on the vector polygon region according to the coarse resolution level to generate the initial unit of the region.

[0057] The vector polygon region to be rasterized and the target resolution level for rasterization are obtained. In this embodiment, the obtained vector polygon region to be rasterized is as follows: Figure 1 The left half is an irregular polygon. A coarse resolution level is determined based on the vector polygon region and the rasterized target resolution level. Figure 6 Three different initial resolutions are selected to generate initial cells for a given vector polygon. When choosing a coarse resolution, the region size and target resolution must be considered comprehensively. If the resolution is too low, the parent cell region covered by the initial internal cells will be too small, increasing the complexity of boundary cell processing and impacting efficiency. Figure 6 The middle n1 level; if it is too high, it will take a long time to generate the initial level during traversal, such as Figure 6 Since there are n3 layers in the middle, this embodiment selects layer n2, which is between the two, as the coarse resolution layer. Through experiments, this invention found that the best results are achieved when the initial resolution is at least 8 layers away from the target resolution and the initial internal sub-units account for less than half of the total. The vector polygon region is rasterized into spherical hexagons according to the determined coarse resolution layer to obtain coarse resolution grid cells, which are then used as the initial cells. Figure 6 As shown, based on the positional relationship between the grid cells and the vector polygon region, they are divided into internal initial cells and boundary initial cells. The internal initial cells refer to the grid cells inside the vector polygon region, while the boundary initial cells refer to the grid cells that intersect with the boundary of the vector polygon region.

[0058] 2. Divide the internal initial unit.

[0059] Internal initial cells refer to the grid cells within a vector polygon region obtained by coarse-resolution hierarchical subdivision, such as... Figure 6 The light-colored grid cell portion. In this embodiment, this portion is partitioned using cross-layer partitioning mode B, directly partitioning the internal initial cells to the target resolution level to generate corresponding sub-cells, where each sub-cell is generated only once. Assuming the initial level (coarse resolution level) and the target level (target resolution level) are n and m respectively, the set of coordinates of the sub-cells generated at the target level for each internal initial cell is represented as C′. m-n For this embodiment, Figure 6 The initial level selected is n2, and assuming the target level is n2+4, this invention performs partitioning according to cross-layer partitioning mode B. The partitioning results and local details are as follows: Figure 7 As shown.

[0060] 3. Divide the initial boundary elements.

[0061] To ensure the integrity of the rasterized cells, a cross-layer partitioning pattern A with complete sub-cells is used. Boundary initial cells are partitioned into even-numbered layers with continuous intervals. The hierarchical recursive partitioning process of the boundary initial cells is as follows: Figure 5 As shown, when the initial level and the target level are n and m respectively, three types of units are separated as follows: (1) Internal sub-units of each intermediate resolution n+2k layer, k∈N + And k < (mn) / 2; (2) the outer sub-units of each intermediate resolution n+2k layer; (3) the boundary sub-units of the m-2 layer closest to the target resolution. These three types of units will be further subdivided to generate the target resolution grid unit. Taking the even-numbered layer subdivision scheme as an example, such as Figure 4 As shown in the flowchart, the initial level and the target level are n and m, respectively. First, the initial boundary unit at level n is partitioned into n+2 levels using the cross-level partitioning mode A, resulting in n+2 sub-units. Figure 8 This diagram illustrates the sub-units after a recursive subdivision of a boundary parent unit, specifically the subdivision result of n+2 layers. The n+2 layers of sub-units include n+2 layers of internal sub-units within the vector polygon region, n+2 layers of external sub-units outside the vector polygon region, and n+2 layers of boundary sub-units intersecting the vector polygon region. Then, it is determined whether n+4 satisfies the condition of being less than or equal to m-4 or m-2. If so, the n+2 layer of boundary sub-units is subdivided to n+4 layers using cross-layer subdivision mode A, resulting in n+4 layers of internal sub-units, n+4 layers of external sub-units, and n+4 layers of boundary sub-units. Figure 9 This is a schematic diagram of the three types of units in the second recursive subdivision; repeat this process until n+2k is greater than m-4, to obtain the internal sub-units of each intermediate resolution level, the external sub-units of each intermediate resolution level, and the boundary sub-units of the m-2 level.

[0062] Theoretically, the number of intervals can be selected according to the requirements. Considering that even-numbered intervals have a consistent pattern and are easy to calculate in actual implementation, this embodiment uses an even-numbered interval method for partitioning.

[0063] 4. Divide the obtained internal sub-units.

[0064] Using mode B, the internal sub-units separated in step 3 are directly subdivided to the target resolution level. Mode B can only guarantee the uniqueness of the target level units generated by units at the same level. The m-level sub-units generated by units at different levels and the m-level sub-units of different initial units may be generated repeatedly. Therefore, it is necessary to check the uniqueness of the units.

[0065] This invention proposes uniqueness checking conditions for sub-units, as follows:

[0066] For some n+2k (k∈N) + A layer unit has corresponding boundary parent units at each coarse resolution level, such as n+2k2 (k∈N, k2<k). This unit and all its boundary parent units are partitioned to the target level. In the set of child units generated by this unit, the child unit that satisfies the uniqueness requirement must be located in the set of child units of the target level generated by all its boundary parent units.

[0067] like Figure 10 As shown, with Figure 8 For example, the internal sub-units of pattern B are divided to the target resolution. Then, it is checked whether each sub-unit is also a boundary initial unit of pattern B at the target resolution, and units that meet the conditions are generated.

[0068] 5. Divide the external sub-units.

[0069] Using cross-layer partitioning mode B, external sub-units at all levels are directly partitioned to the target resolution level. When the parent unit is located outside the region, its internal sub-units must also be located outside the region. Only the edge sub-units may be related to the vector polygon. Therefore, it is only necessary to use the above uniqueness check conditions to check the uniqueness of the edge sub-units of the external sub-units and then retain the units that intersect with the region.

[0070] like Figure 11 As shown, the gray-filled units are the outer sub-units after the initial boundary unit is partitioned. Only the sub-units on the edge are checked. The units within the three dashed boxes are the units that intersect with the region boundary and need to be retained and generated.

[0071] 6. Subdivide the last-level boundary sub-units.

[0072] Using cross-layer partitioning mode B, the m-2 layer boundary sub-units determined in step 3 are partitioned to the target resolution level. The uniqueness of each sub-unit is checked one by one. The uniqueness check conditions are the same as those in step 4. For sub-units that meet the uniqueness check conditions, the overlap is judged, and only sub-units that overlap with the polygonal region are retained.

[0073] 7. Perform coordinate transformation on the generated sub-units of each target level to obtain the corresponding rasterized units.

[0074] Steps 1-6 generate target resolution hierarchical cells that meet the conditions. These cells use a local integer coordinate system. Based on the conversion relationship between the spherical hexagonal grid system and the integer coordinate system, the cells are converted into DGGS cell addresses or geographic coordinates. Then, the vector polygon rasterization result is output.

[0075] A global discrete grid system is an Earth reference frame composed of a set of discretized cells. Vector data must first be discretized into grid cells before entering the grid system. Therefore, vector polygon rasterization is a prerequisite for all geospatial data processing and analysis within the grid system. Typically, the region is first rasterized, then the data to be processed is quantized into the grid system, and analysis functions are then implemented based on this. Figure 12 This is the quantization result of DEM data after rasterizing a vector polygon in a certain area onto a hexagonal grid system.

Claims

1. A method for vector polygon rasterization of a spherical hexagonal grid system, characterized in that, The method includes the following steps: 1) Obtain the vector polygon region to be rasterized and the target resolution level of rasterization. Determine a coarse resolution level based on the vector polygon region and the target resolution level of rasterization. Perform spherical hexagonal rasterization on the vector polygon region based on the coarse resolution level to obtain coarse resolution grid cells as initial cells. 2) The internal initial unit is directly partitioned to the target resolution level using cross-layer partitioning mode B; the cross-layer partitioning mode B refers to the parent unit generating two types of sub-units, internal and edge, at intervals of multiple grid levels, retaining all internal sub-units and retaining some edge sub-units. 3) The initial boundary unit is partitioned using cross-layer partitioning mode A to obtain the internal sub-units of each intermediate resolution level, the external sub-units of each intermediate resolution level, and the m-2 layer boundary sub-units closest to the target resolution level, where m is the target resolution level; the cross-layer partitioning mode A refers to the generation of internal and edge sub-units by the parent unit at intervals of multiple grid levels, while retaining all internal and edge sub-units. 4) Using cross-layer partitioning mode B, the internal sub-units of each intermediate resolution level and the external sub-units of each intermediate resolution level are directly partitioned to the target resolution level; 5) Use cross-layer partitioning mode B to partition the m-2 layer boundary sub-units closest to the target resolution level to the target resolution level; 6) Convert the coordinate system of each target resolution sub-unit to the DGGS unit address or geographic coordinates. The result after conversion is the vector polygon rasterization result.

2. The vector polygon rasterization method for a spherical hexagonal grid system according to claim 1, characterized in that, When the cross-layer partitioning mode B retains some edge sub-units, the center of the four-hole partitioning is located on one of the three edges of the parent unit, and the center of the three-hole partitioning is located on one of the two edges of the parent unit.

3. The vector polygon rasterization method for a spherical hexagonal grid system according to claim 1, characterized in that, In step 3), the initial boundary unit subdivision is performed recursively, following an even number of consecutively spaced layers. The process is as follows: a. The initial boundary unit of level n is partitioned into n+2 levels using the cross-level partitioning mode A, resulting in n+2 sub-units. The n+2 sub-units include n+2 internal sub-units within the vector polygon region, n+2 external sub-units outside the vector polygon region, and n+2 boundary sub-units intersecting with the vector polygon region. b. Determine whether n+4 satisfies the condition of being less than or equal to m-4 or less than m-2. If it does, divide the n+2 layer boundary sub-units into the n+4 layer using the cross-layer partitioning mode A, resulting in the n+4 layer internal sub-units, n+4 layer external sub-units, and n+4 layer boundary sub-units. c. Repeat step b until n+2k is greater than m-4 to obtain the internal sub-units of each intermediate resolution level, the external sub-units of each intermediate resolution level, and the boundary sub-units of the m-2 level.

4. The vector polygon rasterization method for a spherical hexagonal grid system according to claim 1, characterized in that, In step 4), when directly subdividing the outer subunits of the intermediate resolution level to the target resolution level, only the boundary subunits after subdivision are retained.

5. The vector polygon rasterization method for a spherical hexagonal grid system according to claim 1, characterized in that, It also includes a step of checking the uniqueness of the sub-units obtained from step 4) for the target resolution level. If the uniqueness check condition of the sub-unit is not met, the sub-unit is deleted. The uniqueness check condition of the sub-unit is: the sub-unit must be located in the target resolution level sub-unit set generated by all its boundary parent units at the same time.

6. The vector polygon rasterization method for a spherical hexagonal grid system according to claim 1, characterized in that, It also includes performing a uniqueness check on the boundary sub-units retained after directly subdividing the outer sub-units of the intermediate resolution level to the target resolution level in step 4). For the sub-units that pass the uniqueness check, it is judged whether each sub-unit overlaps with the polygon vector region. If there is no overlap, the sub-unit is directly deleted, and only the sub-units that overlap are retained.

7. The vector polygon rasterization method for a spherical hexagonal grid system according to claim 1, characterized in that, In step 5), when partitioning to the target resolution level using cross-layer partitioning mode B, all sub-units are retained.

8. The vector polygon rasterization method for a spherical hexagonal grid system according to claim 7, characterized in that, Step 5) further includes checking the uniqueness of the sub-units obtained from step 4) for the target resolution level. If the uniqueness check condition of the sub-unit is not met, the sub-unit is deleted. The uniqueness check condition of the sub-unit is: the sub-unit must be located in the target resolution level sub-unit set generated by all its boundary parent units at the same time.

9. The vector polygon rasterization method for a spherical hexagonal grid system according to claim 8, characterized in that, Step 5) further includes judging the sub-units that have undergone uniqueness checks, and judging whether each sub-unit overlaps with the polygon vector region. If there is no overlap, the sub-unit is directly deleted, and only the sub-units that overlap are retained.

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