Method to improve the display speed of high-resolution coastline database on mobile computing platform

Abstract

The present invention relates to the technical field of high-resolution coastline database display, and more specifically, to a method for improving the display speed of a high-resolution coastline database on a mobile computing platform. The method comprises the following steps: setting a scale threshold; calculating the current actual scale; if the actual scale is greater than the scale threshold, using a dynamic triangulation algorithm, combined with a boundary constraint optimization algorithm, to perform triangulation segmentation, rendering and display; if the actual scale is less than or equal to the scale threshold, using a static triangulation algorithm for rendering and discretization display; caching the data near the current display area to a local database. The method for improving the display speed of a high-resolution coastline database on a mobile computing platform improves the display speed of a high-resolution coastline database on a mobile computing platform by combining dynamic triangulation with a boundary optimization algorithm to achieve efficient rendering at a high scale, and static triangulation storage at a low scale.

Description

Technical Field

[0001] The present invention relates to the technical field of high-resolution coastline database display, and in particular to a method for improving the display speed of a high-resolution coastline database on a mobile computing platform. Background Art

[0002] A method for improving the display speed of high-resolution coastline database on mobile computing platforms aims to improve the real-time display performance of large-scale coastline data and optimize map rendering effects at different precisions. Through a real-time algorithm that combines dynamic triangulation with boundary constraint optimization, the triangulation processing volume of convex and concave polygons and the optimized calculation of boundary areas are controlled to achieve fast and accurate rendering at high scales, and the loading speed is improved through multi-level static triangulation storage at low scales.

[0003] Existing methods for improving the display speed of high-resolution coastline databases are usually difficult to achieve both high-precision and efficient rendering at high scales. In addition, since a large amount of real-time calculations need to be performed during display and the vector graphics display content is too large when the scale is less than a threshold, the display speed on mobile computing platforms is too slow, which will cause map loading delays and rendering freezes. In summary, a method for improving the display speed of high-resolution coastline databases on mobile computing platforms is provided. Summary of the invention

[0004] The purpose of the present invention is to provide a method for improving the display speed of a high-resolution coastline database on a mobile computing platform, so as to solve the problem proposed in the above background technology that a large amount of real-time calculations need to be performed during display and the vector graphics display content is too much when the scale is less than a threshold, resulting in too slow display speed on the mobile computing platform, causing map loading delays and rendering jams, and heavy computing burden.

[0005] To achieve the above object, the present invention provides a method for improving the display speed of a high-resolution coastline database on a mobile computing platform, comprising the following steps:

[0006] S1. Set the scale threshold according to the hardware performance and actual needs of the mobile computing platform;

[0007] S2. Calculate the current actual scale according to the current display area and zoom level;

[0008] S3. If the actual scale is greater than the scale threshold, the high-resolution coastline database uses a dynamic triangulation algorithm and combines it with a boundary constraint optimization algorithm to perform real-time triangulation, rendering, and display;

[0009] S4. If the actual scale is less than or equal to the scale threshold, the high-resolution coastline database uses a static triangulation algorithm for rendering and discretization display;

[0010] S5. Cache the data near the current display area to the local database, use the GPS sensor and the user's operation trajectory to predict the area that the user may view next, and load and cache the coastline data at the corresponding scale in advance.

[0011] As a further improvement of the technical solution, in S1, the scale threshold is set according to the hardware performance of the mobile computing platform and actual needs. , the specific steps are as follows:

[0012] S1.1. Obtaining CPU processing performance , GPU rendering performance , memory capacity and bandwidth evaluation values and display resolution Mobile computing platform parameters;

[0013] S1.2. Set the scale threshold according to the scale threshold calculation formula .

[0014] As a further improvement of the technical solution, in S1.2, the scale threshold is set according to the scale threshold calculation formula. , the specific method is as follows:

[0015] ;

[0016] in, is the scale threshold.

[0017] As a further improvement of the technical solution, in S2, the current actual scale is calculated according to the current display area and zoom level. , the specific steps are as follows:

[0018] S2.1. Get screen resolution and screen display geographic range ;

[0019] in, is the number of pixels in the horizontal direction; is the number of pixels in the vertical direction; To show the geographic extent for the level; To display the geographic extent vertically;

[0020] S2.2. Get zoom level , calculate the zoom level Horizontal geographical distance ;

[0021] ;

[0022] in, is the horizontal geographic distance at the initial zoom level;

[0023] S2.3. At zoom level Next, according to the number of pixels in the horizontal direction and horizontal geographical distance Calculate the map corresponding distance ;

[0024] ;

[0025] S2.4. Based on actual geographical distance Calculate actual scale ;

[0026] ;

[0027] in, The actual geographical distance.

[0028] As a further improvement of the technical solution, in S3, if the actual scale is greater than the scale threshold, the high-resolution coastline database adopts dynamic triangulation and combines the boundary constraint optimization algorithm to perform real-time triangulation segmentation, rendering and display. The specific steps are as follows:

[0029] S3.1 If , depending on the zoom level , extracting current display range data and polygon data from a high-resolution coastline database, the polygon data including convex polygons and concave polygons;

[0030] S3.2. Use Delaunay triangulation combined with boundary constraint optimization algorithm to triangulate convex and concave polygons in real time and generate the final triangular mesh ;

[0031] S3.3. Render the triangle mesh in real time using OpenGL ES.

[0032] As a further improvement of the present technical solution, in S3.2, the Delaunay triangulation algorithm is combined with the boundary constraint optimization algorithm to triangulate the convex polygons and concave polygons in real time and generate a triangular mesh. , the specific steps are as follows:

[0033] S3.2.1. Extracting polygon data , where polygon By Vertex Composition, and extract polygons according to the convex and concave characteristics of polygons Boundary point set ;

[0034] S3.2.2. Polygon Boundary point set As input, convex and concave polygons are preliminarily triangulated using Delaunay triangulation to generate an initial triangular mesh. ,in, represents the generated triangle;

[0035] S3.2.3. Use the boundary constraint optimization algorithm to optimize the initial triangle mesh, retaining each set of adjacent boundary vertices , connected triangles and remove the triangle The area is smaller than the preset threshold The triangle , generate the boundary triangle set ;

[0036] S3.2.4, use the center of the circumscribed circle of the boundary triangle as the new vertex for internal filling;

[0037] ;

[0038] in, is the center of the circumcircle of the boundary triangle;

[0039] S3.2.5. Using Generated Internal Vertices Perform Delaunay triangulation on the interior of the polygon to generate a new set of internal triangles ;

[0040] S3.2.6. Merge boundary triangle sets and the internal triangle set Get the final triangle mesh :

[0041] ;

[0042] in, is the final triangle mesh; is the boundary triangle set; is the set of interior triangles.

[0043] As a further improvement of the technical solution, in S3.2.3, the initial triangular mesh is optimized using a boundary constraint optimization algorithm, retaining each set of adjacent boundary vertices , connected triangles and remove the triangle The area is smaller than the preset threshold The triangle , generate the boundary triangle set , the specific method is as follows:

[0044] ;

[0045] ;

[0046] ;

[0047] in, Reason Connected triangles.

[0048] As a further improvement of the technical solution, in S4, the static triangulation algorithm performs rendering and discretization display through adaptive scale selection and multi-level static triangulation storage mechanism;

[0049] If the actual scale is less than or equal to the scale threshold, the high-resolution coastline database uses a static triangulation algorithm for rendering and discretization display. The specific steps are as follows:

[0050] S4.1. Setting different accuracy levels , using a pyramid structure to store high-resolution coastline data in multiple levels, for different accuracy levels , all store levels The triangle mesh ;

[0051] S4.2, if , select a scale closer to the current scale Fixed scale , find the fixed scale The corresponding accuracy level , load the precomputed triangle mesh ;

[0052] S4.3. Rendering precomputed triangle meshes via OpenGL ES , and use the GPU for parallel rendering.

[0053] As a further improvement of this technical solution, in S4.2, if , select a scale closer to the current scale Fixed scale , find the fixed scale The corresponding accuracy level , load the precomputed triangle mesh , the specific method is as follows:

[0054] ;

[0055] ;

[0056] in, Supports a limited number of fixed scales for discretized displays.

[0057] As a further improvement of the technical solution, in S5, the data near the current display area is cached in the local database, the GPS sensor and the user's operation trajectory are used to predict the area that the user may view next, and the coastline data at the corresponding scale is loaded and cached in advance. The specific steps are as follows:

[0058] S5.1. Cache the triangle mesh data of the map area currently viewed by the user and the surrounding extended area into a local database;

[0059] S5.2, the system obtains the user's current location through GPS, and predicts the user's next viewing area based on the user's operation trajectory;

[0060] S5.3. Based on the predicted next viewing area of ​​the user, the triangle mesh data corresponding to the area is loaded into the high-resolution coastline database and cached into the local database.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] 1. In the method for improving the display speed of high-resolution coastline database on mobile computing platforms, based on dynamic triangulation and boundary constraint optimization algorithm, convex polygons and concave polygons can be accurately segmented and optimized in real time, the number of unnecessary triangles can be reduced, and the rendering speed can be improved, especially the computing efficiency can be improved when displaying complex coastline areas.

[0063] 2. In the method of improving the display speed of high-resolution coastline database on mobile computing platforms, adaptive scale selection and multi-level static triangulation storage mechanism are used to achieve rapid loading of pre-calculated triangular meshes at low scales, and GPU parallel rendering is used to significantly reduce the pressure of real-time calculations and ensure smooth display of large-scale maps. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 The figure is a flow chart of the overall method of the present invention. DETAILED DESCRIPTION

[0065] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0066] See also Figure 1 As shown, this embodiment provides a method for improving the display speed of a high-resolution coastline database on a mobile computing platform, comprising the following steps:

[0067] S1. Set the scale threshold according to the hardware performance and actual needs of the mobile computing platform;

[0068] In this embodiment S1, the scale threshold is set according to the hardware performance of the mobile computing platform and actual needs. , the specific steps are as follows:

[0069] S1.1. Obtaining CPU processing performance , GPU rendering performance , memory capacity and bandwidth evaluation values and display resolution Mobile computing platform parameters;

[0070] The CPU's main frequency and multi-core performance affect the speed of polygon triangulation, data processing and rendering;

[0071] The GPU model, video memory size, and graphics processing capabilities directly affect the image rendering speed;

[0072] Memory capacity determines the amount of data that the system can load and process simultaneously, and cache size affects the speed at which data is loaded;

[0073] The device's screen resolution determines the visibility of graphical details;

[0074] S1.2. Set the scale threshold according to the scale threshold calculation formula .

[0075] In S1.2, the scale threshold is set according to the scale threshold calculation formula. , the specific method is as follows:

[0076] ;

[0077] in, is the scale threshold.

[0078] In this embodiment, during the operation of the system, the scale threshold Adjustments can also be made through system feedback; if freezes or delays are detected during the display process, the system can automatically improve , reducing the burden of real-time calculations; if hardware performance allows, the system can lower the threshold and improve the accuracy of real-time rendering.

[0079] S2. Calculate the current actual scale according to the current display area and zoom level;

[0080] In this embodiment S2, the current actual scale is calculated according to the current display area and zoom level. , the specific steps are as follows:

[0081] S2.1. Get screen resolution and screen display geographic range ;

[0082] in, is the number of pixels in the horizontal direction; is the number of pixels in the vertical direction; To show the geographic extent for the level; To display the geographic extent vertically;

[0083] S2.2. Get zoom level , calculate the zoom level Horizontal geographical distance ;

[0084] ;

[0085] in, is the horizontal geographic distance at the initial zoom level;

[0086] S2.3. At zoom level Next, according to the number of pixels in the horizontal direction and horizontal geographical distance Calculate the map corresponding distance ;

[0087] ;

[0088] S2.4. Based on actual geographical distance Calculate actual scale ;

[0089] ;

[0090] in, The actual geographical distance.

[0091] According to the current field of view, the actual geographical distance It refers to the actual distance represented by a certain section of the map on the screen, which can be directly obtained from the coordinate system of the map.

[0092] S3. If the actual scale is greater than the scale threshold, the high-resolution coastline database uses a dynamic triangulation algorithm and combines it with a boundary constraint optimization algorithm to perform real-time triangulation, rendering, and display;

[0093] In this embodiment S3, if the actual scale is greater than the scale threshold, the high-resolution coastline database uses dynamic triangulation and combines the boundary constraint optimization algorithm to perform real-time triangulation segmentation, rendering and display. The specific steps are as follows:

[0094] S3.1 If , depending on the zoom level , extracting current display range data and polygon data from a high-resolution coastline database, the polygon data including convex polygons and concave polygons;

[0095] S3.2. Use Delaunay triangulation combined with boundary constraint optimization algorithm to triangulate convex and concave polygons in real time and generate the final triangular mesh ;

[0096] S3.3. Render the triangle mesh in real time using OpenGL ES.

[0097] In this embodiment S3.2, the Delaunay triangulation algorithm is combined with the boundary constraint optimization algorithm to triangulate the convex polygons and concave polygons in real time and generate a triangular mesh. , the specific steps are as follows:

[0098] S3.2.1. Extracting polygon data , where polygon By Vertex Composition, and extract polygons according to the convex and concave characteristics of polygons Boundary point set ;

[0099] S3.2.2. Polygon Boundary point set As input, convex and concave polygons are preliminarily triangulated using Delaunay triangulation to generate an initial triangular mesh. ,in, represents the generated triangle;

[0100] S3.2.3. Use the boundary constraint optimization algorithm to optimize the initial triangle mesh, retaining each set of adjacent boundary vertices , connected triangles and remove the triangle The area is smaller than the preset threshold The triangle , generate the boundary triangle set ;

[0101] S3.2.4, use the center of the circumscribed circle of the boundary triangle as the new vertex for internal filling;

[0102] ;

[0103] in, is the center of the circumcircle of the boundary triangle;

[0104] S3.2.5. Using Generated Internal Vertices Perform Delaunay triangulation on the interior of the polygon to generate a new set of internal triangles ;

[0105] S3.2.6. Merge boundary triangle sets and the internal triangle set Get the final triangle mesh :

[0106] ;

[0107] in, is the final triangle mesh; is the boundary triangle set; is the set of interior triangles.

[0108] In this embodiment S3.2.3, the initial triangle mesh is optimized using a boundary constraint optimization algorithm, retaining each set of adjacent boundary vertices. , connected triangles and remove the triangle The area is smaller than the preset threshold The triangle , generate the boundary triangle set , the specific method is as follows:

[0109] ;

[0110] ;

[0111] ;

[0112] in, Reason Connected triangles.

[0113] In this embodiment, the preset threshold is a value used to control the area of ​​the triangle, which is used to determine which triangles need to be retained or removed during the boundary constraint optimization process. The basis is as follows:

[0114] Complexity of polygons: For complex polygons, especially those with a lot of depressions and irregular boundaries, a smaller threshold is usually required to retain more details; for more regular polygons, a larger threshold can be set.

[0115] Display accuracy: At high scales, higher display accuracy is required, so It should be smaller to retain more triangle details. At low scales, the triangle display does not require too much detail, so a larger threshold can be set.

[0116] Hardware performance: The hardware performance of the mobile computing platform, such as GPU rendering capabilities and memory size, will also affect the choice of thresholds; high-performance devices can set smaller , while lower-performance devices can set a larger threshold to reduce computing pressure;

[0117] Actual requirements and tuning: In actual applications, Usually determined through testing and tuning. Its value can be fixed or dynamically adjusted based on system performance and current display conditions.

[0118] S4. If the actual scale is less than or equal to the scale threshold, the high-resolution coastline database uses a static triangulation algorithm for rendering and discretization display;

[0119] In this embodiment S4, the static triangulation algorithm performs rendering and discretization display through adaptive scale selection and multi-level static triangulation storage mechanism;

[0120] If the actual scale is less than or equal to the scale threshold, the high-resolution coastline database uses a static triangulation algorithm for rendering and discretization display. The specific steps are as follows:

[0121] S4.1. Setting different accuracy levels , using a pyramid structure to store high-resolution coastline data in multiple levels, for different accuracy levels , all store levels The triangle mesh ;

[0122] The pyramid structure is a multi-resolution data storage method that stores the same data at different resolutions to form a hierarchical structure from low precision to high precision.

[0123] For high-resolution coastline data, the system uses the scale Pre-generate triangle meshes at different accuracy levels , and stored in the corresponding level;

[0124] : Represents the lowest precision triangular mesh, suitable for large-scale zoom display;

[0125] arrive : Indicates a grid with medium to high precision, which is suitable for gradually improving the display precision;

[0126] The pyramid structure stores the triangle mesh data of each level in layers. There is a parent-child relationship between the levels, and the meshes of the lower levels are contained in the meshes of the higher levels:

[0127] Contains coarse-grained triangular meshes;

[0128] In On this basis, some areas were refined;

[0129] Indicates the highest precision, showing the most detailed areas.

[0130] S4.2, if , select a scale closer to the current scale Fixed scale , find the fixed scale The corresponding accuracy level , load the precomputed triangle mesh ;

[0131] S4.3. Rendering precomputed triangle meshes via OpenGL ES , and use the GPU for parallel rendering.

[0132] In this embodiment S4.2, if , select a scale closer to the current scale Fixed scale , find the fixed scale The corresponding accuracy level , load the precomputed triangle mesh , the specific method is as follows:

[0133] ;

[0134] ;

[0135] in, Supports a limited number of fixed scales for discretized displays.

[0136] Fixed scale support: Discrete display supports a limited number of fixed scales, such as 30, 20, 10, 5, 1. When the user's view is close to these scales, the system will select the closest scale for rendering.

[0137] S5, cache the data near the current display area to the local database, use the GPS sensor and the user's operation trajectory to predict the area that the user may view next, and load and cache the coastline data at the corresponding scale in advance;

[0138] In this embodiment S5, the data near the current display area is cached in the local database, the GPS sensor and the user's operation trajectory are used to predict the area that the user may view next, and the coastline data at the corresponding scale is loaded and cached in advance. The specific steps are as follows:

[0139] S5.1. Cache the triangle mesh data of the map area currently viewed by the user and the surrounding extended area into a local database;

[0140] S5.2, the system obtains the user's current location through GPS, and predicts the user's next viewing area based on the user's operation trajectory;

[0141] S5.3. Based on the predicted next viewing area of ​​the user, the triangle mesh data corresponding to the area is loaded into the high-resolution coastline database and cached into the local database.

[0142] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and descriptions are only preferred examples of the present invention, and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for improving the display speed of a high-resolution coastline database on a mobile computing platform, characterized in that: The following steps are involved: S1. Set the scale threshold according to the hardware performance and actual needs of the mobile computing platform ; S2. Calculate the current actual scale based on the current display area and zoom level ; S3. If the actual scale is greater than the scale threshold, the high-resolution coastline database uses a dynamic triangulation algorithm and combines it with a boundary constraint optimization algorithm to perform real-time triangulation, rendering, and display; In S3, if the actual scale is greater than the scale threshold, the high-resolution coastline database uses dynamic triangulation and combines the boundary constraint optimization algorithm to perform real-time triangulation segmentation, rendering and display. The specific steps are as follows: S3.1 If , depending on the zoom level , extracting current display range data and polygon data from a high-resolution coastline database, the polygon data including convex polygons and concave polygons; S3.

2. Use Delaunay triangulation combined with boundary constraint optimization algorithm to triangulate convex and concave polygons in real time and generate the final triangular mesh ; S3.3, real-time rendering of triangle meshes via OpenGL ES; In S3.2, the Delaunay triangulation algorithm is combined with the boundary constraint optimization algorithm to triangulate the convex polygons and concave polygons in real time and generate a triangular mesh. , the specific steps are as follows: S3.2.

1. Extracting polygon data , where polygon By Vertex Composition, and extract polygons according to the convex and concave characteristics of polygons Boundary point set ; S3.2.

2. Polygon Boundary point set As input, convex and concave polygons are preliminarily triangulated using Delaunay triangulation to generate an initial triangular mesh. ,in, represents the generated triangle; S3.2.

3. Use the boundary constraint optimization algorithm to optimize the initial triangle mesh, retaining each set of adjacent boundary vertices , connected triangles and remove the triangle The area is smaller than the preset threshold The triangle , generate the boundary triangle set ; S3.2.4, use the center of the circumscribed circle of the boundary triangle as the new vertex for internal filling; ； in, is the center of the circumcircle of the boundary triangle; S3.2.

5. Using Generated Internal Vertices Perform Delaunay triangulation on the interior of the polygon to generate a new set of internal triangles ; S3.2.

6. Merge boundary triangle sets and the internal triangle set Get the final triangle mesh : ； in, is the final triangle mesh; is the boundary triangle set; is the set of internal triangles; S4. If the actual scale is less than or equal to the scale threshold, the high-resolution coastline database uses a static triangulation algorithm for rendering and discretization display; In S4, the static triangulation algorithm performs rendering and discretization display through adaptive scale selection and multi-level static triangulation storage mechanism; If the actual scale is less than or equal to the scale threshold, the high-resolution coastline database uses a static triangulation algorithm for rendering and discretization display. The specific steps are as follows: S4.

1. Setting different accuracy levels , using a pyramid structure to store high-resolution coastline data in multiple levels, for different accuracy levels , all store levels The triangle mesh ; S4.2, if , select a scale closer to the current scale Fixed scale , find the fixed scale The corresponding accuracy level , load the precomputed triangle mesh ; S4.

3. Rendering precomputed triangle meshes via OpenGL ES , and use GPU for parallel rendering; In S4.2, if , select a scale closer to the current scale Fixed scale , find the fixed scale The corresponding accuracy level , load the precomputed triangle mesh , the specific method is as follows: ； ； in, Supports a limited number of fixed scales for discretized displays; S5. Cache the data near the current display area to the local database, use the GPS sensor and the user's operation trajectory to predict the area that the user may view next, and load and cache the coastline data at the corresponding scale in advance.

2. The method for improving the display speed of a high-resolution coastline database on a mobile computing platform according to claim 1, characterized in that: In S1, the scale threshold is set according to the hardware performance and actual needs of the mobile computing platform. , the specific steps are as follows: S1.

1. Obtaining CPU processing performance , GPU rendering performance , memory capacity and bandwidth evaluation values and display resolution Mobile computing platform parameters; S1.

2. Set the scale threshold according to the scale threshold calculation formula .

3. The method for improving the display speed of a high-resolution coastline database on a mobile computing platform according to claim 2, characterized in that: In S1.2, the scale threshold is set according to the scale threshold calculation formula. , the specific method is as follows: ； in, is the scale threshold.

4. The method for improving the display speed of a high-resolution coastline database on a mobile computing platform according to claim 3, characterized in that: In S2, the current actual scale is calculated according to the current display area and zoom level. , the specific steps are as follows: S2.

1. Get screen resolution and screen display geographic range ; in, is the number of pixels in the horizontal direction; is the number of pixels in the vertical direction; To show the geographic extent for the level; To display the geographic extent vertically; S2.

2. Get zoom level , calculate the zoom level Horizontal geographical distance ; ； in, is the horizontal geographic distance at the initial zoom level; S2.

3. At zoom level Next, according to the number of pixels in the horizontal direction and horizontal geographical distance Calculate the map corresponding distance ; ； S2.

4. Based on actual geographical distance Calculate actual scale ; ； in, The actual geographical distance.

5. The method for improving the display speed of a high-resolution coastline database on a mobile computing platform according to claim 4, characterized in that: In S3.2.3, the initial triangle mesh is optimized using a boundary constraint optimization algorithm, retaining each set of adjacent boundary vertices , connected triangles and remove the triangle The area is smaller than the preset threshold The triangle , generate the boundary triangle set , the specific method is as follows: ； ； ； in, Reason Connected triangles.

6. The method for improving the display speed of a high-resolution coastline database on a mobile computing platform according to claim 5, characterized in that: In S5, the data near the current display area is cached in the local database, the area that the user may view next is predicted by using the GPS sensor and the user's operation trajectory, and the coastline data at the corresponding scale is loaded and cached in advance. The specific steps are as follows: S5.

1. Cache the triangle mesh data of the map area currently viewed by the user and the surrounding extended area into a local database; S5.2, the system obtains the user's current location through GPS, and predicts the user's next viewing area based on the user's operation trajectory; S5.

3. Based on the predicted next viewing area of ​​the user, the triangle mesh data corresponding to the area is loaded into the high-resolution coastline database and cached into the local database.

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