ew ol.Feature({
          geometry: new ol.geom.Point(node.coordinate),
          node: node
        });
        feature.setId(node.id);
        nodes.addFeature(feature);
      }

      function edgeToFeature(edge) {
        var feature = new ol.Feature({
          geometry: new ol.geom.LineString(edge.coordinates),
          edge: edge
        });
        feature.setId(edge.id);
        edges.addFeature(feature);
      }

      function faceToFeature(face) {
        var coordinates = topo.getFaceGeometry(