How can I search for elements within a polygon with Overpass?

I am new to Overpass API and GIS in general.

Is there an easy way to export all buildings in a specific region using coordinates to specify the polygon? I couldn't find a solution using the wiki and google so far.

I have large sets of coordinates which are determining some medium-voltage grids.

Or is there another tool I could use? I want to use the polygon- coordinates of the exported buildings in matlab.

Thanks for your help!

Solution

Overpass API provides the (poly: ) filter to query objects inside a given polygon. See the documentation in the wiki for details.

Buildings in a given polygon can be queried as follows:

way[building](poly:"50.7 7.1 50.7 7.12 50.71 7.11");
(._;>;);
out meta;

Due to a recent memory limitation, you might have to either add a [maxsize: xxx] setting:

[maxsize:2073741824];
way[building](poly:"50.7 7.1 50.7 7.12 50.71 7.11");
(._;>;);
out;

or resort to the following workaround to force another evaluation sequence:

way(poly: "50.7 7.1 50.7 7.12 50.71 7.11");
way._[building];
(._;>;);
out meta;