2. Map slicing technique#
Map Tiles, translated into map tiles and map slices. In this book, it is considered that map slicing pays more attention to the process of operation, so the term “map tile” is adopted.
If you want to improve the access speed of Web maps, using map slicing is a very effective method. Map slicing is to configure the map under multiple scale, and then draw the map under each scale as a small picture in advance and save it in a directory called cache on the server. In this way, when the client accesses the map, it can directly get the small pictures needed and splice them into the whole map, instead of dynamically creating a picture by the server and sending it to the client, thus greatly improving the access speed.
There are many technical solutions for map slicing, and there are many open source tools for map slicing, which is a basic tool in all kinds of FOSS software at present. MapServer has MapCache module, GeoServer has GeoWebCache module to create map slices; TileMill and CartoCSS markup languages can create map slices in a more flexible way; and there are common gadgets such as GeoWebCach, TileCache, TileStache, Tile-Server and MapProxy. There are other tools that people know less about.
The Mapnik library is a free and open source software written in C++ callable from Python and other languages for creating map tiles. Mapnik is an efficient rendering engine that includes advanced drawing options not found in common WMS layers. Although the use of Mapnik is not very convenient, it usually requires some knowledge of Linux and some experiments and mistakes, but for profit, Mapbox recently released an open source program called TileMill, which can be run on Mac and Windows, with Mapnik as the bottom layer, providing a beautiful window interface, thus simplifying the drawing process.
- 2.1. Principle of map tiles
- 2.2. Use GetMap to generate slices
- 2.3. Installation and use of MapProxy
- 2.4. MapProxy case: a layer
- 2.5. MapProxy case: multiple layers
- 2.6. MapProxy case: layer merging