The challenge

Your current map provider gives you two things:

• A set of ’tiles’ (square map images) that are placed together to make the map
• A JavaScript API, or equivalent library for mobile apps, to view them

To switch to OpenStreetMap, you’ll need to replace both of these.

The tiles

The map tiles, images of (usually) 256 x 256 pixels each, are drawn (“rendered”) from a map database.

If you currently use Google Maps, you’ll be using Google’s map tiles, hosted at google.com. Because the OpenStreetMap Foundation is a non-profit organisation with limited resources, you can’t just slot in the tiles from openstreetmap.org as a replacement (see the Tile Usage Policy). Instead, you can:

• Generate your own tiles, by downloading the free OSM map database and rendering them;

• Or use a third-party supplier (some of whom charge, some are free)

The OSM map database is called planet.osm. The full database and regular update files are both available at planet.openstreetmap.org.

Rendering your own tiles gives you complete control over their appearance. You can customise the maps to appear any way you like. Alternatively, third-party suppliers have OSM expertise and may have ready-prepared map styles that you can use.

The API/library

There is no single canonical library: you can choose whichever suits your needs best. The two most popular JavaScript libraries for displaying OSM tiles are:

• OpenLayers – powerful and long-established

• Leaflet – lightweight and easy-to-learn

APIs are also available for mobile platforms, such as Route-Me (iOS) and osmdroid (Android).

The licence

Unlike commercial providers’ data, OpenStreetMap is ‘open data’. The map data is available to you free-of-charge, with the freedom to copy and modify. OSM’s licence is the Open Database Licence.

Your obligations are:

• Attribution. You must credit OpenStreetMap with the same prominence that would be expected if you were using a commercial provider. See OSM’s copyright guidelines.

• Share-Alike. When you use any adapted version of OSM’s map data, or works produced with it, you must also offer that adapted database under the ODbL.