anchor.diff:      });
     }
     return tileservers;
  +}
  +
  +function intereactionsServer( ) {
  +  var interactionTileURL = "<%= CONFIG.tile_servers.interactions %>";
  +  if( interactionTileURL ) { return "//" + interactionTileURL; }
  +  return elasticsearchTileservers()[0];
   }
   
   google.maps.Map.prototype.addObservationsLayer = function(options) {
  
positive.code:       interactivity = options.interactivity;
    if( options.interactivity ) {
      // windshaft needs the interactivity param to know what data to render
      options.grids = _.map( tileURLs, function( l ) {
        return google.maps.Map.prototype.interactivityURL( l, options.interactivity );
      })
    }
  
negative.code:     }), {
      maxzoom: gridmaxzoom,
      interactivity: options.interactivity === false ? false : 'id',
      interactionsURL: intereactionsServer( ) + gridTileSuffix,
      disabled: options.disabled
    });
    pointLayer = this.addTileLayer( _.map( tileservers , function( base ) {
  