A UAV-based mapping method

Abstract

The present invention provides a drone-based mapping method, comprising: slicing a drone image to obtain a plurality of tiles; mapping the pixel coordinates of each tile onto the drone image to obtain global pixel coordinates of each tile; converting the global pixel coordinates of each tile into geographic coordinates based on the drone's horizontal azimuth angle p, vertical azimuth angle t, viewing angle z, and elevation h; and mapping each tile onto a map based on a pyramid scheme based on the geographic coordinates of each tile, thereby completing the mapping. The present invention slices the entire drone image and then fuses and plots the tiles onto a map, using image slicing technology to improve the accuracy of the fusion of each local map captured.

Description

Technical Field

[0001] The present invention relates to the field of map drawing, and more particularly to a map drawing method based on a drone. Background Art

[0002] With the development of drone technology, monitoring and regulatory services are placing higher demands on real-time drone monitoring. For example, combining drone video streams with spatiotemporal data to provide a more intuitive understanding of the actual situation in the target area is crucial. To meet this demand, the efficient and accurate conversion of real-time drone footage into geographic coordinates and integration with maps has become a pressing technical challenge.

[0003] Currently, drone photography images are usually drawn on maps. Since drone photography images have a large range, if the entire image is fused at once, local accuracy may be poor. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, the present invention provides a drone-based map drawing method to overcome the problem of poor accuracy caused by fusing the entire drone image at one time.

[0005] The present invention provides a method for mapping based on an unmanned aerial vehicle, comprising:

[0006] Slice the drone image to obtain multiple tiles;

[0007] Map the pixel coordinates of each tile to the drone image to obtain the global pixel coordinates of each tile;

[0008] Convert the global pixel coordinates of each tile into geographic coordinates according to the drone's horizontal azimuth angle p, vertical azimuth angle t, viewing angle z, and drone's elevation h;

[0009] According to the geographic coordinates of each tile, based on the pyramid scheme, each tile is drawn on the map to complete the map drawing.

[0010] The present invention provides a drone-based map drawing method, which slices the entire drone image and then fuses it and draws it on the map. It uses image slicing technology to improve the accuracy of the fusion of each local map of the photography. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A flowchart of a drone-based mapping method provided in an embodiment of the present invention;

[0012] Figure 2 This is a schematic diagram of drone image slicing;

[0013] Figure 3Schematic diagram of the mapping relationship from tile pixels to global pixels;

[0014] Figure 4-1 Schematic diagram of the geometric relationship between the imaging center and the imaging range according to one embodiment;

[0015] Figure 4-2 Schematic diagram of the geometric relationship between the imaging center and the imaging range of another embodiment;

[0016] Figure 5 Schematic diagram of the vertical azimuth ray of the UAV in an embodiment of the present invention;

[0017] Figure 6 Schematic diagram for calculating the geographic coordinates of tiles. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 making creative work are within the scope of protection of the present invention. In addition, the technical features in the various embodiments or single embodiments provided by the present invention can be arbitrarily combined with each other to form a feasible technical solution. This combination is not restricted by the sequence of steps and / or structural composition mode, but must be based on the ability of ordinary technicians in this field to implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0019] In the process of map drawing based on drone photography, since the drone has a large range of photographic images, if the entire image is fused at once, local accuracy may be poor. This solution uses image slicing technology to improve the accuracy of the fusion of each local map.

[0020] Figure 1 A flowchart of a method for mapping based on drones provided by the present invention is shown in FIG. Figure 1 As shown, the method includes:

[0021] Step 1: Slice the drone image to obtain multiple tiles.

[0022] For details, see Figure 2 , for the entire drone image, slice the drone image into square slices according to row and column numbers, with w as the slice width, to get the pixel range of each tile:

[0023] Where, is the tile in the i-th column and j-th row, 、 、 、 are the minimum x pixel value, minimum y pixel value, maximum x pixel value, and maximum y pixel value of the tile, respectively, and w is the slice width.

[0024] Step 2: Map the pixel coordinates of each tile to the drone image to obtain the global pixel coordinates of each tile.

[0025] It is understandable that step 1 slices the entire drone image to obtain the pixel range of each tile, see Figure 3 This step maps the pixel coordinates of each tile to the drone image to obtain the global pixel coordinates of each tile on the drone image.

[0026] Specifically, establish a mapping relationship between tile pixel coordinates and the global pixel coordinates of the drone image:

[0027]

[0028] Where, For the mapping relationship, Represents the pixel with coordinates (x, y) in the tile at column i and row j, mapped to the global pixel coordinates of the drone image , w represents the tile width.

[0029] Step 3: Convert the global pixel coordinates of each tile into geographic coordinates according to the horizontal azimuth angle p, vertical azimuth angle t, viewing angle z and altitude h of the drone.

[0030] It can be understood that according to the mapping relationship in step 2, the pixel coordinates of the four corner points of each tile are mapped to global pixel coordinates. Specifically, given that the pixel coordinates of the four points of each tile are [(0,0), (w,0), (w,w), (0,w)], its global pixel coordinates can be calculated as follows:

[0031]

[0032]

[0033]

[0034]

[0035] Where, 、 、 、 are the global pixel coordinates of the four points of the tile, i is the tile column number, and j is the tile row number.

[0036] After mapping the pixel coordinates of each tile to global pixel coordinates, the global pixel coordinates of each tile are converted to geographic coordinates.

[0037] In one embodiment of the present invention, converting the global pixel coordinates of each tile into geographic coordinates according to the horizontal azimuth angle p, the vertical azimuth angle t, the viewing angle z, and the elevation h of the drone includes:

[0038] Step 31: Map the pixel coordinates of each tile to the global pixel coordinates in the drone image. .

[0039] It can be understood that according to the mapping relationship in step 2, the pixel coordinates of each tile are mapped to the global pixel coordinates of the drone photo. The global pixel coordinates in the tile are expressed as .

[0040] Step 32: Based on the vertical azimuth angle t of the drone, the longitudinal component of the viewing angle and the ordinate of the global pixel point , calculate the vertical azimuth angle of the global pixel point on the ray where it is located, wherein the ray is formed by connecting the drone camera point and the global pixel point.

[0041] Among them, let the horizontal azimuth angle of the drone be p, the vertical azimuth angle be t, the viewing angle be z, the altitude of the drone be h, the width of the drone image be W, and the height be H.

[0042] According to the full viewing angle z, the half angle of the longitudinal component of the viewing angle can be calculated and the transverse component half angle , see Figure 4-1 and Figure 4-2 ,in, Figure 4-1 The bottom plane is the camera range plane, P is the camera center point, PO is the perpendicular line from point P to the bottom surface, and MO is the perpendicular line from point O to an edge of the bottom surface. Figure 4-2 ON is the perpendicular line from point O to the other side of the base.

[0043]

[0044]

[0045] Known is half of the viewing angle, h is the altitude of the drone, and the length of the AO can be calculated:

[0046]

[0047] Further, calculate Value:

[0048]

[0049] Further, calculate the length of MO:

[0050]

[0051] Further, calculate the length of MA and NO:

[0052]

[0053] Finally, the longitudinal component half angle can be calculated :

[0054]

[0055]

[0056] See Figure 5 , calculate the vertical azimuth of the global pixel point on the ray, including the following steps:

[0057] According to the vertical azimuth angle t of the UAV and the half angle z1 of the longitudinal component of the viewing angle, the starting vertical azimuth angle t1 of the UAV photograph is calculated:

[0058] ;

[0059] According to the vertical coordinate of the global pixel point , calculate the angle of the longitudinal component of the ray formed by connecting the drone camera point and the global pixel point. The ratio of the photographic pixel to the drone photo height is the ratio of the ray angle to the longitudinal viewing angle. Calculate the angle occupied by the longitudinal component of the ray of the global pixel point. :

[0060] ;

[0061] Among them, H is the height of the UAV image;

[0062] According to the starting vertical azimuth angle t1 of the drone photography and the vertical coordinate of the global pixel point , calculate the vertical azimuth of the global pixel point on the ray :

[0063] .

[0064] In step 33, the vertical azimuth angle of the global pixel point on the ray and the elevation of the drone are used to calculate the geographical distance r of the global pixel point relative to the drone.

[0065] Among them, according to the vertical azimuth angle of the global pixel point on the ray , the elevation h of the UAV, the elevation error value of the UAV and the elevation error value of the global pixel point , calculate the geographical distance r of the global pixel relative to the drone: ;

[0066] Among them, the elevation error value of the drone The elevation error value of the global pixel point is calculated based on the geographic coordinates of the drone. is the unknown number to be found.

[0067] Specifically, step 32 calculates the vertical azimuth of the global pixel point on the ray The distance r between the global pixel point and the drone can be calculated based on the above formula. The actual geographical location of the drone is known, so the altitude h of the drone is also known. The altitude error value of the drone is It can be calculated based on the geographic coordinates of the drone. Since the geographic coordinates of the global pixel point are unknown and need to be solved, the elevation error value of the global pixel point is It is also unknown and needs to be solved later.

[0068] Step 34, according to the horizontal azimuth angle p of the drone, the horizontal component of the viewing angle and the horizontal coordinate of the global pixel point , calculate the horizontal azimuth angle of the global pixel point on the ray where it is located, wherein the ray is formed by connecting the drone camera point and the global pixel point.

[0069] It is understandable that the above calculations are based on the vertical azimuth of the global pixel point on the ray. , it is also necessary to calculate the horizontal azimuth angle of the global pixel point on the ray.

[0070] In one embodiment of the present invention, the horizontal azimuth angle p of the drone, the horizontal component of the viewing angle and the horizontal coordinate of the global pixel point are used. , calculating the horizontal azimuth angle of the global pixel point on the ray, including:

[0071] According to the horizontal coordinate of the global pixel point And the half angle z2 of the horizontal component of the drone's perspective, calculate the angle between the drone's camera point and the global pixel point to form a ray on the horizontal component. The angle is the ratio of the pixel's horizontal coordinate value to the width of the drone's photo, and calculate the angle occupied by the global pixel point on the horizontal component of the ray. :

[0072] ;

[0073] Where W is the width of the UAV image;

[0074] According to the horizontal azimuth angle p of the UAV and the half angle z2 of the horizontal component of the viewing angle, the starting horizontal azimuth angle p1 of the UAV photo is calculated:

[0075] ;

[0076] According to the starting horizontal azimuth angle p1 of the drone image and the angle occupied by the lateral component of the global pixel point in the ray , calculate the horizontal azimuth angle of the global pixel point on the ray : .

[0077] Step 35 , calculating the geographic coordinates of the global pixel point based on the geographic coordinates of the drone, the geographical distance r of the global pixel point relative to the drone, and the horizontal azimuth angle of the global pixel point on the ray where the global pixel point is located.

[0078] See also Figure 6 , where the solution equation for the geographic coordinates of the global pixel point is:

[0079] ;

[0080] ;

[0081] ;

[0082] in, 、 is the geographic coordinate of the global pixel point, 、 is the geographic coordinate of the UAV, r is the geographic distance between the global pixel point and the UAV, h is the elevation of the UAV, is the elevation error value of the UAV, which is calculated based on the geographic coordinates of the UAV. is the elevation error value of the global pixel point, which is the unknown number to be solved.

[0083] In the above solution equation for the geographic coordinates of tile pixels, 、 and The unknown number that needs to be solved. For a specific pixel point in the tile, its geographic coordinates 、 It is certain that the elevation error value Then in the solution process, we can use multiple sets of global pixel points on the vertical azimuth of the ray and the horizontal azimuth of the global pixel point on the ray , to establish equations and fit the equations to solve them.

[0084] Since the vertical azimuth of the global pixel point in the ray and the horizontal azimuth of the global pixel point on the ray It is calculated based on the drone's horizontal azimuth angle p, vertical azimuth angle t and viewing angle z.

[0085] Therefore, the drone can shoot the same pixel at different attitude angles (including horizontal azimuth angle p, vertical azimuth angle t and viewing angle z). For a drone attitude angle, the vertical azimuth angle of a group of global pixels on the ray can be calculated. and the horizontal azimuth of the global pixel point on the ray The multiple attitude angles of the UAV can obtain multiple sets of . Substitute into the above geographic coordinate solution equation, 、 and , the geographic coordinates of each tile can be solved.

[0086] Step 4: According to the geographic coordinates of each tile, based on the pyramid scheme, each tile is drawn on the map to complete the map drawing.

[0087] It can be understood that according to step 3, the geographic coordinates of each pixel in each tile are calculated, and each tile is sequentially drawn on the map through the pyramid scheme, thereby completing the real-time video fusion.

[0088] In one embodiment of the present invention, each tile is drawn onto a map based on a pyramid scheme according to the geographic coordinates of each tile, thereby completing map drawing, including:

[0089] Step 41 : Calculate the number of tiles that the map view can accommodate at the current level according to the map view size of the current level and the pixel size of each tile.

[0090] It is understandable that the coordinates of the center point of the current map (x c ,y c ), view screen size , at the current pyramid level, a mapping relationship between geographic coordinates and map screen coordinates can be established.

[0091] Calculate the geographic span of a tile at the current level:

[0092] ;

[0093] ;

[0094] Where, 、 They are the geographical span corresponding to a tile at the current pyramid level, 、 The maximum and minimum values ​​of the top tile x geographic coordinates, 、 is the maximum and minimum y value of the top tile, is the current level.

[0095] Calculate the number of tiles that the map view can accommodate at the current level:

[0096] ;

[0097] ;

[0098] Where, 、 are the number of rows and columns of the current level tiles, is the current screen height, is the pixel height of a tile, is the current screen width, The pixel width of a tile.

[0099] Step 42 : Calculate the map range of the map view at the current level according to the center point coordinates and the number of tiles of the map view at the current level.

[0100] The map range of the map view at the current level is calculated based on the center point coordinates and the number of tiles of the map view at the current level, including:

[0101]

[0102]

[0103]

[0104]

[0105] Where, 、 They are the horizontal and vertical coordinates of the center point of the map view, 、 、 、 The map extents of the current map view respectively.

[0106] Step 43 : Based on the map range of the map view at the current level, the geographic coordinates of each tile are mapped to the map view window coordinates.

[0107] Among them, based on the map range of the map view at the current level, the geographic coordinates of each tile are mapped to the map view window coordinates, including:

[0108] ;

[0109] ;

[0110] Where, 、 They are the horizontal and vertical coordinates of the converted map view window respectively.

[0111] Step 44 : Based on the map view window coordinates of each tile, each tile is drawn on the map view to complete the map drawing.

[0112] It is understandable that the geographic coordinates of each tile are converted to the map view window coordinates at the current level, and each tile is drawn on the map view based on the map view window coordinates of each tile to complete the map drawing.

[0113] The present invention provides a drone-based map drawing method, which improves the accuracy of local areas and thus the accuracy of the entire map drawing by slicing the drone map, independently calculating each tile, and finally fusing them.

[0114] It should be noted that, in the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0115] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0116] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0117] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0118] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0119] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0120] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for mapping based on drones, characterized in that: include: Slice the drone image to obtain multiple tiles; Map the pixel coordinates of each tile to the drone image to obtain the global pixel coordinates of each tile; Convert the global pixel coordinates of each tile into geographic coordinates according to the drone's horizontal azimuth angle p, vertical azimuth angle t, viewing angle z, and drone's elevation h; According to the geographical coordinates of each tile, based on the pyramid scheme, each tile is drawn on the map to complete the map drawing; The method converts the global pixel coordinates of each tile into geographic coordinates according to the horizontal azimuth angle p, vertical azimuth angle t, viewing angle z and elevation h of the drone, including: Map the pixel coordinates of each tile to the global pixel coordinates in the drone image ; According to the vertical azimuth angle t of the drone, the longitudinal component of the viewing angle and the longitudinal coordinate of the global pixel point , calculating the vertical azimuth angle of the global pixel point on the ray where it is located, wherein the ray is formed by connecting the drone camera point and the global pixel point; Calculate the geographical distance r of the global pixel point relative to the drone based on the vertical azimuth angle of the global pixel point on the ray and the altitude of the drone; According to the horizontal azimuth angle p of the UAV, the lateral component of the viewing angle and the horizontal coordinate of the global pixel point , calculating the horizontal azimuth angle of the global pixel point on the ray where it is located, wherein the ray is formed by connecting the drone camera point and the global pixel point; The geographic coordinates of the global pixel point are calculated according to the geographic coordinates of the drone, the geographical distance r of the global pixel point relative to the drone, and the horizontal azimuth angle of the global pixel point on the ray where the global pixel point is located.

2. The method for mapping based on drones according to claim 1, characterized in that: The drone image is sliced ​​to obtain multiple tiles, including: With w as the slice width, square slice the drone image to get the pixel range of each tile: Where, is the tile in the i-th column and j-th row, 、 、 、 are the minimum x pixel value, minimum y pixel value, maximum x pixel value, and maximum y pixel value of the tile, respectively, and w is the slice width.

3. The method for mapping based on drones according to claim 2, characterized in that: Mapping the pixel coordinates of each tile to the drone image to obtain the global pixel coordinates of each tile includes: Establish a mapping relationship between tile pixel coordinates and the global pixel coordinates of the drone image: Where, For the mapping relationship, Represents the pixel with coordinates (x, y) in the tile at column i and row j, mapped to the global pixel coordinates of the drone image , w represents the slice width.

4. The method for mapping based on drones according to claim 1, wherein: The vertical azimuth angle t of the drone, the longitudinal component of the viewing angle and the longitudinal coordinate of the global pixel point , calculating the vertical azimuth angle of the global pixel point on the ray, including: According to the vertical azimuth angle t of the UAV and the half angle z1 of the longitudinal component of the viewing angle, the starting vertical azimuth angle t1 of the UAV photograph is calculated: ； According to the vertical coordinate of the global pixel point , calculate the angle between the drone camera point and the global pixel point on the longitudinal component of the ray, and calculate the angle occupied by the global pixel point on the longitudinal component of the ray : ； Among them, H is the height of the UAV image; According to the starting vertical azimuth angle t1 of the drone photography and the angle occupied by the longitudinal component of the global pixel point in the ray , calculate the vertical azimuth of the global pixel point on the ray : 。 5. The method for mapping based on drones according to claim 1, characterized in that: Calculating the geographical distance r of the global pixel point relative to the drone based on the vertical azimuth angle of the ray and the altitude of the drone, including: According to the vertical azimuth angle of the global pixel point on the ray , the elevation h of the UAV, the elevation error value of the UAV and the elevation error value of the global pixel point , calculate the geographical distance r of the global pixel relative to the drone: ; Among them, the elevation error value of the drone The elevation error value of the global pixel point is calculated based on the geographic coordinates of the drone. is the unknown number to be found.

6. The method for mapping based on drones according to claim 1, characterized in that: According to the horizontal azimuth angle p of the drone, the horizontal component of the viewing angle and the horizontal coordinate of the global pixel point , calculating the horizontal azimuth angle of the global pixel point on the ray, including: According to the horizontal coordinate of the global pixel point And the half angle z2 of the horizontal component of the drone's perspective, calculate the angle between the drone's camera point and the global pixel point to form a ray on the horizontal component, and calculate the angle occupied by the global pixel point on the horizontal component of the ray : ； Where W is the width of the UAV image; According to the horizontal azimuth angle p of the UAV and the half angle z2 of the horizontal component of the viewing angle, the starting horizontal azimuth angle p1 of the UAV photo is calculated: ； According to the starting horizontal azimuth angle p1 of the drone image and the angle occupied by the lateral component of the global pixel point in the ray , calculate the horizontal azimuth angle of the global pixel point on the ray : .

7. The method for mapping based on drones according to claim 6, characterized in that: Calculating the geographic coordinates of the global pixel point based on the geographic coordinates of the drone, the geographical distance r of the global pixel point relative to the drone, and the horizontal azimuth of the global pixel point on the ray where the global pixel point is located includes: ； ； ； in, 、 is the geographic coordinate of the global pixel point, 、 is the geographic coordinate of the UAV, r is the geographic distance between the global pixel point and the UAV, h is the elevation of the UAV, is the elevation error value of the UAV, which is calculated based on the geographic coordinates of the UAV. is the elevation error value of the global pixel point, and is the unknown number to be solved; According to the vertical azimuth angles of multiple groups of different global pixel points on the ray and the horizontal azimuth of the global pixel point on the ray , calculate the geographical coordinates of the global pixel point through the calculation equation of the geographical coordinates of the global pixel point, and solve to obtain the geographical coordinates of the global pixel point and the elevation error value of the global pixel point ; Among them, the drone is used to shoot at multiple sets of different horizontal azimuth angles p, vertical azimuth angles t and viewing angles z. For each set of horizontal azimuth angles p, vertical azimuth angles t and viewing angle z of the drone, the vertical azimuth angle of the corresponding global pixel point on the ray is calculated. and the horizontal azimuth of the global pixel point on the ray .

8. The method for mapping based on drones according to claim 1, wherein: The process of drawing each tile onto a map based on the geographic coordinates of each tile and the pyramid scheme to complete the map drawing includes: Calculate the number of tiles that can be accommodated in the map view at the current level based on the map view size of the current level and the pixel size of each tile; Calculate the map range of the map view at the current level based on the center point coordinates and the number of tiles of the map view at the current level; Based on the map extent of the map view at the current level, the geographic coordinates of each tile are mapped to the map view window coordinates; Based on the map view window coordinates of each tile, each tile is drawn on the map view to complete the map drawing.

9. The method for mapping based on drones according to claim 8, characterized in that: The calculation of the number of tiles that the map view can accommodate at the current level based on the map view size of the current level and the pixel size of each tile includes: Calculate the geographic span of a tile at the current level: ； ； Where, 、 They are the geographical span corresponding to a tile at the current pyramid level, 、 The maximum and minimum values ​​of the top tile x geographic coordinates, 、 is the maximum and minimum y value of the top tile, is the current level; Calculate the number of tiles that the map view can accommodate at the current level: ； ； Where, 、 are the number of rows and columns of the current level tiles, is the current screen height, is the pixel height of a tile, is the current screen width, is the pixel width of a tile; Calculating the map range of the map view at the current level according to the center point coordinates and the number of tiles of the map view at the current level includes: Where, 、 They are the horizontal and vertical coordinates of the center point of the map view, 、 、 、 They are the map extents of the current map view respectively; Mapping the geographic coordinates of each tile to map view window coordinates based on the map extent of the map view at the current level includes: ； ； Where, 、 They are the horizontal and vertical coordinates of the converted map view window respectively.

Images