code: public void initialize(UnitType unitType, double unitLength, Coordinate position) {
  		if (null == unitType) {
  			throw new IllegalArgumentException("please provide a unitType");
  		}
  
  		this.unitType = unitType;
  		this.unitLength = unitLength;
  
  		backGround = new Rectangle((null == getId() ? "" : getId() + "-bg"));
  		backGround.setBounds(new Bbox(0, 0, 5, MARKER_HEIGHT + 2 * VERTICAL_PADDING));
  		backGround.setStyle(STYLE_BACKGROUND);
  		leftMarker = new Rectangle((null == getId() ? "" : getId() + "-lm"));
  		leftMarker.setStyle(STYLE_MARKER);
  		leftMarker.setBounds(new Bbox(0, 0, 1, MARKER_HEIGHT));
  
  		rightMarker = new Rectangle((null == getId() ? "" : getId() + "-rm"));
  		rightMarker.setStyle(STYLE_MARKER);
  		rightMarker.setBounds(new Bbox(0, 0, 1, MARKER_HEIGHT));
  		bottomLine = new Rectangle((null == getId() ? "" : getId() + "-bm"));
  		bottomLine.setStyle(STYLE_MARKER);
  		bottomLine.setBounds(new Bbox(0, 0, 0, 1));
  		distance = new Text((null == getId() ? "" : getId() + "-text"));
  		distance.setStyle(STYLE_FONT);
  
  		dummy = new Rectangle(getId() + "-dummy");
  		dummy.setStyle(new ShapeStyle("#FFFFFF", 0, "#FFFFFF", 0, 0));
  		dummy.setBounds(new Bbox(0, 0, 1, 1));
  	}
docs: Initialize scale bar.
  
  @param unitType
  how are units shown (english/metric/crs)
  @param unitLength
  length of a unit in meter
  @param position
  coordinate where scalebar should be drawn on the graphics context