/**
     * Adds marker to center of the screen and returns its coordinate
     *
     * @return coordinate added
     */
    private GeoCoordinate selectPosition() {
      Point center = new Point(map.getWidth() / 2, map.getHeight() / 2);
      GeoCoordinate gc = map.pixelToGeo(center);

      if (marker == null) {
        // create new marker
        marker = mapFactory.createStandardMarker(gc, 10, null, MapStandardMarker.BALLOON);
        map.addMapObject(marker);
      } else {
        // move existing marker
        marker.setCoordinate(gc);
      }
      return gc;
    }