Basic Knowledge of Map Tiles
The story begins with a global shading map made by the map Engineer in the team. This map uses global terrain data and superimposes the main vegetation information to show the ups and downs of the global surface. The color is soft and it is very suitable for use as the base map of other maps. But the problem is that the volume of global terrain data is more than 100g, so it is very inconvenient to transmit such a large volume of data. Is there a way to directly use this map without copying the data?
Map tiles can solve this problem well. First, the map is generated into map tiles, and then the tiles are published as services to access the map in the form of services. Because there is no need to use the original data, you can access the map anytime and anywhere. The map is widely used, and many application platforms are displayed in the form of map tiles. What are the map tiles? What knowledge is involved? Now I bring you the most comprehensive answer!
- Is there a more intuitive explanation for map tiles?
Map tile is to generate m * n pictures of each scale map according to a certain size. When browsing, it grabs pictures according to certain rules to form a complete map. Publishing tiles as services can greatly reduce the burden of server and network bandwidth, and improve the speed of map browsing. At present, it is widely used in public map service, sharing service platform, space-time information cloud platform and other fields. SuperMap idesktopx provides a format for generating grid tiles and vector tiles.
2. How to choose grid tile and vector tile?
Vector tiles have some advantages in tile storage space and tile rendering efficiency, but there are also some limitations in use. Only vector data can support vector tiles. Vector and grid data can generate grid tiles. The world shading map is based on grid data, so only grid tiles can be used. The specific comparison between vector tile and grid tile is shown in the table below:
3. How to select the type of grid tile generated?
SuperMap iDesktopX supports the generation of PNG, webp, JPG, dxtz and other grid tile types. It is recommended to generate grid tiles in webp format. Webp format is a new image file format introduced by Google in 2010. Compared with traditional tile types, the advantage is that the volume of tiles can be greatly reduced while ensuring the same image quality, and the volume of the file can be reduced by about 80% compared with the same PNG format. Not only the disk space is saved, but also the execution rate is significantly increased when the tile read and tile merge operations are performed.
4. Where are the recommended tile results generated?
SuperMap iDesktopX supports local storage and mongodb database storage. Mongodb database is recommended to facilitate tile management and fast access based on the distributed storage and retrieval capability of the database. At the same time, mongodb database storage tile is also convenient for copy migration.
5. How long does it take to generate tiles from 100G data? How to be more efficient?
Multi task cutting can significantly improve the efficiency of cutting. After testing and verification, ordinary PC, nationwide electronic map, cut scale for the 14th layer of the global subdivision "1:18055". It takes 8.25 hours to cut a single process, and it can be reduced to about 1.44 hours by eight processes.
6. What management operations can be performed on the generated tile data?
SuperMap iDesktopX provides tile management tools:
(1) Change storage mode: you can migrate the original or compact historical tile data stored in the local area to mongodb library for management.
(2) Tile merging: edge images are automatically fused and connected, which is suitable for the management of production and operation database.
(3) Tile distribution: supports extracting specified range and scale tiles from the master library.
7. Previously, only level 12 tiles were generated, but now level 13 tiles are needed. Do you want to regenerate all tiles?
No need! SuperMap iDesktopX offers two solutions:
(1) Tile update: add level 13 tiles to the target library directly through tile update function. Update operation supports single task mode and multi task mode.
(2) Tile management: through tile management function, level 13 tiles are merged into existing level 12 tiles. Tile management also supports multi task mode, which can significantly improve the merger efficiency. User data test shows that when 450.2g tiles are merged into 755.9g tile library, the single process time of the machine with better performance is about 111 hours, and the multi process time can be reduced to 13 hours. The figure below shows the efficiency change of the combined tiles on a common PC.
At the end of the story, through the publishing tile service function provided by SuperMap idesktopx, the generated map tiles are published as online services and hosted on SuperMap online. Successfully turn 100g data into online service, no matter where you are now, as long as you can access it https://maptiles.supermapol.com/iserver/services/map-Hillshade/rest/maps Then you can use the global shading map as the base map.
