     layers: [raster, facesLayer, edgesLayer, nodesLayer],
        target: 'mapol',
        view: new ol.View({
          center: [-11000000, 4600000],
          zoom: 16
        })
      });

      var topo = topolis.createTopology();

      topo.on('addnode', nodeToFeature);
      topo.on('removenode', function(e) {
        removeElementFeature(nodes, e);
      });
      topo.on('addedge', edgeToFeature);
      topo.on('modedge', function(e) {
        var feature = edges.getFeatureById(e.id);
        feat