In Great Britain most geodata that provides the reference and geographic context for more targeted user datasets created by individual organisations is issued by Ordnance Survey®. These user datasets may include Sites of Specifi c Scientifi c Interest or Basic Land and Property Units. Based on this reference data, users often integrate other datasets, such as statistical tables or their own geo-datasets, to support analysis and decision making. Others may collect geo-datasets by using Global Positioning System (GPS) equipment: the location of street furniture, for example. In all cases it is vital that data from different sources fi ts together spatially to enable the joint use and analysis.