protected void showCenterPoint(Position cPos) {
      // Display the center point in red.
      PointPlacemarkAttributes selectedLocationAttributes;
      selectedLocationAttributes = new PointPlacemarkAttributes();
      selectedLocationAttributes.setLineMaterial(Material.RED);
      selectedLocationAttributes.setScale(8d);
      selectedLocationAttributes.setUsePointAsDefaultImage(true);

      PointPlacemark pm = new PointPlacemark(cPos);
      pm.setAltitudeMode(WorldWind.RELATIVE_TO_GROUND);
      pm.setAttributes(selectedLocationAttributes);
      pm.setValue(AVKey.DISPLAY_NAME, cPos.toString());
      pm.setLineEnabled(true);
      this.gridLayer.addRenderable(pm);
    }
    protected void showGrid(List<Position> grid, Position cPos) {
      this.gridLayer.removeAllRenderables();

      // Display the grid points in yellow.
      PointPlacemarkAttributes gridPointAttributes;
      gridPointAttributes = new PointPlacemarkAttributes();
      gridPointAttributes.setLineMaterial(Material.YELLOW);
      gridPointAttributes.setScale(6d);
      gridPointAttributes.setUsePointAsDefaultImage(true);

      for (Position p : grid) {
        PointPlacemark pm = new PointPlacemark(p);
        pm.setAltitudeMode(WorldWind.RELATIVE_TO_GROUND);
        pm.setAttributes(gridPointAttributes);
        pm.setLineEnabled(true);
        pm.setValue(AVKey.DISPLAY_NAME, p.toString());
        this.gridLayer.addRenderable(pm);
      }

      showCenterPoint(cPos);
    }