I'm trying to get a clean vector layer from an elevation raster layer. I'm using Raster > Extraction > Contour... to get lines from the elevation raster here:
This tool produces this layer (I kept only one elevation level to keep it simple here):
I'm then using Vector > Geometry tools > Lines to polygons to transform these lines into polygons and it produces this result:
The problem is: All the parts which are below the main elevation contour are filled. But those should be holes in the main polygon.
How can I get the polygon with the holes?