code: public static double distance( LasRecord r1, LasRecord r2 ) {
          double distance = NumericsUtilities.pythagoras(r1.x - r2.x, r1.y - r2.y);
          return distance;
      }
docs: Projected distance between two points.
  
  @param r1 the first point.
  @param r2 the second point.
  @return the 2D distance.