Ordnance Survey has launched a new, free map of all the publicly accessible green spaces in Great Britain. For the first time, we can find out how many public parks, gardens, playgrounds, playing fields, woods, allotments etc there are; where they are; how big they are. Not only will it help people find their nearest green space – and this was the Government’s motivation for undertaking the project - this data is vital for green space managers and a more detailed map, for local authorities, is available through OS Mastermap Greenspace. Historically, green space managers have lacked the basic data other asset managers take for granted: robust information about the location, type and quality of the assets under their control. This new, authoritative map is a significant first step – and could help strengthen the case for more public investment in green infrastructure. However, more data is needed. Until we have commonly accepted standards for the quality of green infrastructure it is difficult for managers to measure return on investment. Nevertheless, for anyone interested in understanding, valuing and improving the country’s green infrastructure, OS Open Greenspace is a welcome, and potentially very powerful, resource.