/**
*
* @param x
* - X cordination of the query point
* @param y
* - Y cordination of the query point
* @return the q point with updated Z value (z value is as given the
* triangulation).
*/
public double z(double x, double y)
{
Point_dt q = new Point_dt(x, y);
Triangle_dt t = find(q);
return(t.z_value(q));
}
