OpenStreetMap: 'It's the Wikipedia of maps'

A map of the world that anyone can edit
Steve Coast, OpenStreetMap
Steve Coast of OpenStreetMap. Photograph: Kaela Domenico for the Observer

When Steve Coast created OpenStreetMap in 2004, he had to build the world from scratch. "We started with absolutely nothing, a completely blank canvas. The first data came from me cycling around Regent's Park with a GPS puck the size of a pack of cards and then plugging it into my laptop." His eventual aim? To map the entire planet and make the data freely available, without copyright restrictions, for everyone with an internet connection to use in a multitude of ways.

Now, eight years on from Regent's Park, most of the world has been mapped, in varying degrees of detail, and can be viewed on and on numerous other services that use the site's data. But Coast, who is 31, didn't do this all by himself. He has been helped by more than half a million registered contributors from around the world who have mapped their local areas, added details and corrected mistakes on a voluntary basis, without expectation of payment. It's no surprise that Coast describes his project as "the Wikipedia of maps".

Adopting the same "open source" philosophy that made Wikipedia the biggest reference site on the web, OpenStreetMap allows users "to tinker with the underlying data or the underlying software that produces it". This is what sets the project apart from other free online map services, such as the ubiquitous Google Maps. "If you don't like any aspect of something and want to change it you're free to do so. We're giving people the freedom to play with the data, whereas [other services] keep it to themselves."

Contributors have responded to the challenge in a variety of imaginative ways. "They don't just add things like turn restrictions and roads and so on," says Coast. "They go further and add footpaths and parks and cycling paths and hiking trails and a million other types of data. I stopped keeping track when people started adding base-jumping spots."

The majority of contributors are based in Europe, and consequently you'll find more detailed information about bus stops or hospitals or house numbers in London, where Coast started the project, than in Luanda or Lhasa – but there are some surprises. Kibera, the second largest slum in Africa, was a blank spot on the map until local volunteers took to it with GPS devices in November 2009 and filled in the blanks. During the 2010 Haiti earthquake, "the most complete digital map of Haiti's roads, hospitals, triage centres and refugee camps", according to the New York Times, was built by OpenStreetMap volunteers.

The project has benefited from advances in technology since 2004 as well as help from well-endowed sponsors. "In the early days you needed a GPS, but today, Microsoft, where I now work, donates all its aerial imagery to OpenStreetMap so you can just look at aerial pictures and draw the features on top of them. The other lower barrier is that now everyone has a mobile phone with a GPS system and maps on it."

The project tends to attract people with specific interests in cartography, information technology and the open source movement, but Coast is hoping to broaden the project's appeal by making it effortless to contribute. "There'll be a tipping point relatively soon when it will not make sense to use any other kind of data. We're going to look back and wonder why we ever had maps that were any other way."