This week's lesson focuses on tiled web maps. Tiles are relatively small square-shaped "chunks" of data (either rasterized map images or raw vector coordinates) that have been pregenerated by the server and stored in a directory called a cache. When web users navigate the map, the server can just hand out the tiles rather than generating the map on the fly.
In this lesson, you'll learn the pros and cons of tiled maps, as well as strategies for building and maintaining a tile cache. You will learn about traditional rasterized tiled image formats, as well as a newer generation of tiles that store vector coordinates. Because rasterized image tiles have been around much longer and have mature support from tile generating engines, tile servers, and clients, most of the lesson content focuses on these types of tiles. The newer vector tile format is discussed near the end of the lesson content.
There are two walkthroughs associated with this lesson, both of which involve rasterized image tiles because these currently have the most mature tools for end-to-end FOSS workflows. The first walkthrough shows how to create a simple cache of your Philadelphia neighborhoods map using the GeoWebCache software that is integrated into GeoServer. In the second walkthrough, you'll use TileMill and a markup language called CartoCSS to create a Philadelphia basemap cache with some nicer cartography than you would get using GeoServer.
- Describe the advantages of tiled web maps and identify when it is appropriate to use them.
- Recognize strategies and techniques for creating and updating large tiled web maps.
- Describe the differences between rasterized image tiles and vector tiles, and the reasons that each might be used
- Create tiles for a WMS using GeoWebCache.
- Use best practices in multiscale map design to create a tiled basemap using TileMill.
- Discuss hosting options for tiled maps. Unpack and upload your tiled map to your own web space (on PASS).
- Read the Lesson 5 materials on this page.
- Complete the two walkthroughs.
- Complete the Lesson 5 assignment.