Blog of Claudius Hauptmann

OpenStreetMap is a collaborative project to create a free editable map of the world. The maps are created using data from portable GPS devices, aerial photography and other free sources [Wikipedia]. OpenStreetMap data can be used freely under the terms of the Creative Commons Attribution-ShareAlike 2.0 license [OpenStreetMap]. Thus it can be used e.g. in your own applications, mobile devices or web pages, for productive use or testing purposes (This abstract makes no claim to be complete, please read the license before using the data).

The database model is documented here. OpenStreetMap provides two ways for programmatical use/access. First, snapshots and diffs that can be imported in your own database and be used for replication (The files are here). Second, an API (implemented as a REST webservice). This link queries a mountain peak in bavaria, for example (Look at the source code, if the browser displays a blank page). If you are just interested in looking up some points of interest from time to time and internet access is available, using the API is a good idea. Otherwise an export or  replication (full or partial) of the database is the better solution, particularly if you want to run intensive geospatial computings on the data.

You do not have to write your own client code to access the API. JOSM, a java-based map editor for OpenStreetMap is using the web service to load the map content and store your change set. Perhaps it is a good idea to look at the source code and the api calls. I tried to check out the project via eclipse (with subclipse) and I just had to click debug as java application and it worked fine, since the required libraries are included in the svn repository. Then I could debug through the code and watch the API calls. Unfortunately there is much GUI code mixed into the logic, but the code is easy to understand.

If you want to export/replicate the data into your own data store, there is a really great java-based console application: Osmosis. It can be run within cron jobs to periodically to replicate the database. I checked out the source code, but had some troubles debugging the application, since not all libraries are included in the svn repository. It took some time to collect all necessary jar files from the web. I advise you not to grub through the code. There is a lot of functionality out of the box, which can be read here and there is an API to write your own plugins for Osmosis, that can be included in the pipelines, if you want to use your own database schema, e.g. with Hibernate Spatial like in my last post about how to store your map data on the server side. A really great feature is the option –read-change-interval, that calculates, which change sets have to be downloaded to keep your own replication of the database up to date.