How good is OpenStreetMap information ? A comparative study of OpenStreetMap and Ordnance Survey datasets for London and the rest of England

Within the framework of Web 2.0 applications, the most striking example of a geographical application is the OpenStreetMap project. OpenStreetMap aims to create a free digital map of the world and is implemented through the engagement of participants in a mode similar to software development in Open Source projects. The information is collected by many participants, collated on a central database and distributed in multiple digital formats through the World Wide Web (Web). Within Geographical Information Science (GIScience) research, Mike Goodchild suggested a term for this type of information: ‘Volunteered Geographical Information’ (VGI). However, to date there has been no systematic analysis of the quality of VGI. This paper aims to fill this gap by analysing the quality of OpenStreetMap information for London and England by comparing it to Ordnance Survey datasets. As OpenStreetMap started in London in August 2004, the analysis of the information for the London area provides the best understanding of the achievements and difficulties of VGI. The analysis shows that OpenStreetMap information can be fairly accurate: on average within about 6 metres of the position recorded by the OS, and with approximately 80% overlap of motorway objects between the two datasets. In the space of four years, OpenStreetMap has captured about 29% of the area of England, of which approximately 4% are digitised lines without a complete set of attributes. Importantly, most of the data capture (80%) was carried out by 90 participants and a very large group of users disengaged from the project after minimal contribution. The paper concludes with some suggestions for future developments and research directions.