Latest release also brings new enhancements and bug fixes
TileMill 0.5.0 is now available, with the biggest addition being support for using SQLite databases as geographic datasources. This gives TileMill cartographers an alternative geographic data source to shapefiles and the ability to join multiple databases from different sources together into one source. TileMill 0.5.0 has several smaller enhancements that you can see in the changelog, and Konstantin will blog about the new Mac OS X features later this week.
TileMill now supports using SQLite to make custom maps
SQLite files are an ideal alternative to shapefiles because they consist of just one file, making them very easy to share, and just like shapefiles, SQLite databases can store geographic features along with non-geographic attributes about those features. They are easy to edit with free tools like Quantum GIS, and feature attributes can be edited with any SQLite client. Performance wise, our test show that SQLite layer performance is about equal to that of shapefiles, and TileMill will even automatically index your SQLite database if an index is missing.
Joining multiple SQLite files
The real power of having SQLite in TileMill is the ability to join two or more SQLite databases together. This feature allows you supplement your geographic data with data from other sources and use it in your stylesheets and tooltips.
For example, say you have a database that contains polygons for each park in your city. You set up a web application that gathers ratings from citizens about each park and shows the results on a map that is updated once a week. Since the parks’ polygons don’t change very often, that database can remain static from week to week. The ratings however are quite dynamic and will be different each week. You could configure your web application to export the ratings data as an SQLite database, allowing you to join in the new data for your map each week, without bothering with the polygon data.