/**
     * Performs one line of sight calculation between the reference position and a specified grid
     * position.
     *
     * @param gridPosition the grid position.
     * @throws InterruptedException if the operation is interrupted.
     */
    protected void performIntersection(Position gridPosition) throws InterruptedException {
      // Intersect the line between this grid point and the selected position.
      Intersection[] intersections = this.terrain.intersect(this.referencePosition, gridPosition);
      if (intersections == null || intersections.length == 0) {
        // No intersection, so the line goes from the center to the grid point.
        this.sightLines.add(new Position[] {this.referencePosition, gridPosition});
        return;
      }

      // Only the first intersection is shown.
      Vec4 iPoint = intersections[0].getIntersectionPoint();
      Vec4 gPoint =
          terrain.getSurfacePoint(
              gridPosition.getLatitude(), gridPosition.getLongitude(), gridPosition.getAltitude());

      // Check to see whether the intersection is beyond the grid point.
      if (iPoint.distanceTo3(this.referencePoint) >= gPoint.distanceTo3(this.referencePoint)) {
        // Intersection is beyond the grid point; the line goes from the center to the grid point.
        this.addSightLine(this.referencePosition, gridPosition);
        return;
      }

      // Compute the position corresponding to the intersection.
      Position iPosition = this.terrain.getGlobe().computePositionFromPoint(iPoint);

      // The sight line goes from the user-selected position to the intersection position.
      this.addSightLine(this.referencePosition, new Position(iPosition, 0));

      // Keep track of the intersection positions.
      this.addIntersectionPosition(iPosition);

      this.updateProgress();
    }
  protected String formatMeasurements(Position pos) {
    StringBuilder sb = new StringBuilder();

    /*
     //sb.append(this.unitsFormat.areaNL(this.getLabel(AREA_LABEL), this.getArea()));
     sb.append(this.unitsFormat.lengthNL(this.getLabel(PERIMETER_LABEL), this.getLength()));
    */

    // sb.append(this.unitsFormat.lengthNL(this.getLabel(WIDTH_LABEL),
    // this.shape.getEastWestRadius() * 2));
    // sb.append(this.unitsFormat.lengthNL(this.getLabel(LENGTH_LABEL),
    // this.shape.getNorthSouthRadius() * 2));
    // sb.append(this.unitsFormat.lengthNL(this.getLabel(HEIGHT_LABEL),
    // this.shape.getVerticalRadius() * 2));

    // sb.append(this.unitsFormat.angleNL(this.getLabel(HEADING_LABEL), this.shape.getHeading()));

    // if "activeControlPoint" is in fact one of the control points
    if (!this.arePositionsRedundant(pos, this.polygon.getReferencePosition())) {
      sb.append(this.unitsFormat.angleNL(this.getLabel(LATITUDE_LABEL), pos.getLatitude()));
      sb.append(this.unitsFormat.angleNL(this.getLabel(LONGITUDE_LABEL), pos.getLongitude()));
      sb.append(this.unitsFormat.lengthNL(this.getLabel(ALTITUDE_LABEL), pos.getAltitude()));
    }

    // if "activeControlPoint" is the shape itself
    if (this.polygon.getReferencePosition() != null) {
      sb.append(
          this.unitsFormat.angleNL(
              this.getLabel(CENTER_LATITUDE_LABEL),
              this.polygon.getReferencePosition().getLatitude()));
      sb.append(
          this.unitsFormat.angleNL(
              this.getLabel(CENTER_LONGITUDE_LABEL),
              this.polygon.getReferencePosition().getLongitude()));
      sb.append(
          this.unitsFormat.lengthNL(
              this.getLabel(CENTER_ALTITUDE_LABEL),
              this.polygon.getReferencePosition().getAltitude()));
    }

    return sb.toString();
  }
  protected void moveControlPoint(
      ControlPointMarker controlPoint, Point lastMousePoint, Point moveToPoint) {
    View view = this.wwd.getView();
    Globe globe = this.wwd.getModel().getGlobe();

    Position refPos = controlPoint.getPosition();
    if (refPos == null) return;

    Line ray = view.computeRayFromScreenPoint(moveToPoint.getX(), moveToPoint.getY());
    Line previousRay = view.computeRayFromScreenPoint(lastMousePoint.getX(), lastMousePoint.getY());

    Vec4 vec = AirspaceEditorUtil.intersectGlobeAt(this.wwd, refPos.getElevation(), ray);
    Vec4 previousVec =
        AirspaceEditorUtil.intersectGlobeAt(this.wwd, refPos.getElevation(), previousRay);

    if (vec == null || previousVec == null) {
      return;
    }

    Position pos = globe.computePositionFromPoint(vec);
    Position previousPos = globe.computePositionFromPoint(previousVec);
    LatLon change = pos.subtract(previousPos);

    java.util.List<LatLon> boundary = new ArrayList<LatLon>();
    for (LatLon ll : this.polygon.getOuterBoundary()) {
      boundary.add(ll);
    }

    boundary.set(controlPoint.getIndex(), new Position(pos.add(change), refPos.getAltitude()));

    // ExtrudedPolygon ensures that the last boundary position is the same as the first. Remove the
    // last point
    // before setting the boundary.
    boundary.remove(boundary.size() - 1);

    this.polygon.setOuterBoundary(boundary);
  }