Is the building footprint layer available by itself in GIS format? |
Not as such (strictly speaking, there aren't "layers" in OSM as such), but you can extract the data (have a look at some of these questions for how to do that - you'll probably end up using XAPI or Overpass). You'd be looking for ways tagged "building=*", I'd imagine. Once you've got the data, you'd then want to do something with it yourself of course - for example, if you want to render some tiles showing just building footprints you'd need to render it. |