In our [previous posts](http://www.pbs.org/idealab/2010/08/tilemill-custom-maps-to-help-with-data-dumps-hyper-local215.html) on [TileMill](http://mapbox.com/tools/tilemill), we’ve focused on how [open data can be used to create custom maps](http://www.pbs.org/idealab/2010/09/open-data-custom-maps-better-afghan-election-monitoring259.html)and [tell unique stories](http://www.pbs.org/idealab/2010/08/helping-dc-drinkers-and-bikers-with-custom-maps230.html). One question we run into a lot is, “Where does open data come from?”

One exciting source is a global mapping project called [OpenStreetMap](http://www.openstreetmap.org/) (OSM). Founded in 2004 with the goal of creating a free and open map of the world, OSM now boasts over 300,000 contributors and has comparable or better data for many countries than the popular proprietary or closed datasets. The premise is simple and powerful: Anyone can use the data, and anyone can help improve it.

![OSM-based map of Port au Prince made with TileMill](http://farm5.static.flickr.com/4086/5078913335_554ca4ddc4.jpg)

With this huge amount of data, activity, and adoption, we’re excited about how [TileMill](http://mapbox.com/tools/tilemill) is going to give more people ways to leverage OSM data to make their own maps. Users will be able to mash up OSM data on their own using TileMill and turn it into their very own custom map.

  1. Humanitarian OpenStreetMap Team

To get a sense of the practicality of OSM, just look at [the role it played in the response to the January 12 earthquake in Haiti](http://www.newyorker.com/online/blogs/closeread/2010/02/a-map-of-thousands.html). Reliable maps are critical to disaster response efforts and there simply wasn’t much data available for the affected areas. Within hours of the quake, the OSM community mobilized and hundreds of volunteers from all over the world began tracing available satellite imagery, importing available datasets, and coordinating with relief workers on the ground to ensure that new data was being created and distributed in ways that would best support their work.

Using OpenStreetMap as a platform and leveraging the existing, engaged community paid off — within days, volunteers had created the best available maps of Port au Prince and nearby cities. OSM data quickly [appeared on the GPS devices of search and rescue teams](http://news.bbc.co.uk/2/hi/uk_news/magazine/8517057.stm), and in the planning tools of the international response community.

Members of the [Humanitarian OpenStreetMap Team](http://wiki.openstreetmap.org/wiki/Humanitarian_OSM_Team) (HOT) have continued to support the use of OSM in Haiti through trainings with local NGOs, the Haitian government, and international responders. In November, the fifth deployment of HOT team members to Haiti to support the International Organization for Migration (IOM) in their work to map the camps for people displaced by the earthquake, using OSM as a platform.

Through this effort by the OSM community, anyone looking to make a map of Haiti has a great database of roads, hospitals, and even collapsed buildings that they can use in their work. We see this kind of data sharing as important capacity-building to help people make useful custom maps. With TileMill, we’re working to create a practical toolset for working with this data.

  1. Beyond Haiti

Moving beyond Haiti and thinking about maps of other places, what’s exciting about OpenStreetMap is the hundreds of community groups around the world getting together and using OSM to map their own cities and neighborhoods. If a map data doesn’t exist yet, there’s a chance that it could through the efforts of the OSM community. For instance, the image below is a picture of work the local OSM community did in Washington, DC, to [make a very detailed map of the National Zoo](http://www.flickr.com/photos/ajturner/3916389470/in/set-72157622232619705/).

![Mapping the National Zoo in Washington, DC by ajturner](http://farm3.static.flickr.com/2527/3915606827_448d665510.jpg)

If you’re looking for open map data for your next project, a great place to start would be to [reach out to the local OSM community in your area](http://wiki.openstreetmap.org/wiki/Mapping_projects) — there’s a good chance they can help you figure out how to get it.