code: private double getStartAngle() {
          ScaleDirection scaleDirection = gauge.getScaleDirection();
          Pos            knobPosition   = gauge.getKnobPosition();
          switch(knobPosition) {
              case TOP_CENTER   : return ScaleDirection.CLOCKWISE == scaleDirection ? angleRange * 0.5 : -angleRange * 0.5;
              case BOTTOM_CENTER:
              default           : return ScaleDirection.CLOCKWISE == scaleDirection ? 180 + angleRange * 0.5 : 180 - angleRange * 0.5;
          }
      }
docs: ******************** Private Methods ***********************************