All local planning authorities are required to publish and maintain Brownfield land registers as open data (see The Town and Country Planning (Brownfield Land Register) Regulations 2017). Land is classed as brownfield if it has been previously developed. You can see Calderdale’s Brownfield land register at DataWorks: Brownfield land register.
All registers are required to follow a common csv file format, which makes it easier to combine registers from different local planning authorities. The defined format includes a requirement for longitude and latitude coordinates – which calls for a map!
Stuart Lowe at ODI Leeds decided to take on the challenge of creating an interactive map using the registers from all five West Yorkshire local authorities. You can see the result at West Yorkshire brownfield site map.
Stuart also wrote about the challenges of the project (including the Kirklees data ‘going on holiday’!!), which details how it was done, and how the project was able to highlight data errors that possibly would not have been otherwise found, see ODI blog: Brownfield land registers.