It's disappointing that less than two-thirds of gardens are covered by vegetation.
Less than two thirds of garden space in Britain's towns and cities is covered with greenery such as plants, lawns and trees, analysis suggests.
The Office for National Statistics' Data Science Campus and Ordnance Survey combined techniques to classify images with aerial imagery to test ways to identify the amount of green space in urban residential gardens.
Initial results estimate that 62 percent of garden spaces are covered with vegetation in Great Britain, a finding the Royal Horticultural Society described as "disappointing" as greenery cools cities, curbs flooding and helps wildlife.
The work aims to give a more accurate report of green spaces than previous estimates which have assumed 100 percent of their area is covered by vegetation rather than factoring in features such as patios and paths.
As part of the project, the team focused on Cardiff and Bristol and found that around 54 percent of Cardiff's urban residential gardens were covered by greenery, compared to around 45 percent of Bristol's.
Tom Smith, managing director at the ONS Data Science Campus, said: "Through our work with Ordnance Survey we've developed a new tool to provide more accurate estimates of how much of our gardens are covered with vegetation than has previously been suggested.
"This tool is intended to be useful to policy makers when planning a wide range of different measures from flood risk through to estimating the country's carbon footprint.
"Through our Data Science Campus we are looking at how new cutting edge techniques can help improve the way we look at data. These techniques will help with our mission to mobilise the power of data to help Britain make better decisions and improve lives."
Hayley Monckton, from the RHS, said: "It's disappointing that less than two-thirds of gardens are covered by vegetation, when green gardens are so beneficial for our health, for wildlife and for the environment. Plants and gardens can help cool towns and cities and mitigate flooding - things we will see more of as our climate changes."
The RHS has a "greening Great Britain" campaign which calls on people to plant and grow more plants in their own outside spaces and community areas.
"The trend to pave increases chances of flooding and means you miss out on all the benefits of plants, such as helping to reduce pollution and providing food for our pollinators. We can all make a positive difference one plant at a time," she said.
Paul de Zylva, nature campaigner at Friends Of The Earth, said: "People's gardens can be brilliant for wildlife but there is increasingly less space for nature than we might think.
"Covering gardens in artificial grass, concrete, and paving for parking and patios is bad news for nature, for soaking up flood water and for absorbing carbon. Fortunately, gardens also present a clear opportunity for people to help the planet as they are one of the few places where people have direct control."
Emily Beament is the PA environment correspondent. Image: home thods.