Return to Vol. 3 Issue 6, December 2008

What the Heck is … OpenStreetMap?

By in Vol. 3 Issue 6, December 2008

Mumbai as documented in OpenStreetMap.

In the United States, we have a general policy of the federal government sharing useful data with the public. This policy has led to open distribution of geospatial data sets that include the Census Bureau’s TIGER line file, USGS topographic maps, aerial photography, land cover and elevation, a plethora of NASA imagery and even several global data sets developed by the military. This overall openness has been replicated by many U.S. cities and states as well.

While Canada and Australia have a similar legal tradition to the U.S. and some government GIS data is available, most developed countries in Europe and around the world make little or no geospatial data available to the public. In the United Kingdom, the Ordnance Survey maintains the most comprehensive and high quality national GIS database in the world, but the data is only available to the public for a steep licensing fee. In the developing world, data is either not distributed due to national security concerns or simply does not exist.

With the Census Bureau’s TIGER data as a starting point, private companies in the United States began building high quality base maps for commercial sale. These companies have grown and consolidated until there are only a small number that dominate the market, and the two largest, TeleAtlas and NavTeq, are now held by consumer electronics firms. These companies maintain global data sets, but the cost of licensing them is substantial.

It is within this environment of high costs and limited access to data that a project called OpenStreetMap began in the U.K. Inspired by collaborative information commons such as Wikipedia, OpenStreetMap is an editable map of the whole world, which is being built largely from scratch using GPS traces and other personal surveys. It is released with an open content license and available for free to anyone that wishes to use it. The project is a combination of software, data and knowledge. A variety of software tools have been developed to support online and off-line editing of the map data as well as its maintenance and distribution. A wiki is used to organize information about standards and processes.

Copenhagen as documented in OpenStreetMap.

Like other open data projects, such as Wikipedia or the Human Genome Project , the effort is not perfect. For example, there is not yet a standard mechanism for storing the data necessary to perform geocoding and routing; the concept of place name aliases is relatively weak; there is no formalized review process to identify and eliminate deliberate vandalism; the spatial data model is limited to points and lines; and while there are standards for what are valid attributes for each feature, they are not enforced, so the implementation of data elements is not yet very consistent. Nonetheless, the effort is growing rapidly and improving with time. There are now thousands of people building the map in almost every part of the world, and the size of the global database (known as ‘the planet file’) is now doubling every six months.

OpenStreetMap is a compelling example of how the power of loosely organized collective action can be brought to bear to create sophisticated new knowledge resources. In some parts of the world, OpenStreetMap is now more comprehensive than what is commercially available, and it will doubtless continue to develop. Azavea staff are both contributing to the database and exploring new ways to leverage the resulting map. If you would like to participate in its development, there are a number of resources online that will help you learn how. If you live in Philadelphia and would like to help improve the map, I’m organizing a Meetup in January and you are invited!