I have added a layer with tracks and track points from OSM in QQGIS and exported this GPX file into an shapefile. Now I wanted to calculated the area of the buildings. I tried to do this with the tracks which also distribute the outlines of the different buidlings. But the function $area did not work in the attribute table. So how can I get the GPX file or shape file with tracks and trackpoints into a layer with polygons?
This a picture of the track and trackpoint layer. I need the areas of all buildings to do a furter calculations.