“…Suppose a fitting plane expressed by ax + by + cz = d , where a , b , and c are unit normal vectors of the plane, satisfying a 2 + b 2 + c 2 = 1 and d ≥ 0. For four space points denoted by { P n ( x n , y n , z n ), n = 1,2,3,4}, a recognized optimization program for determining the fitting plane parameters ( a , b , c , d ) can be used, To solve the above optimal program, let s n = | ax n + by n + cz n – d | and a penalty function with the Lagrange multiplier is defined by The derivative of eq with respect to d is obtained as By letting eq be zero, it yields Similarly, by letting the derivative of eq with respect to a , b , c be zero, respectively, there follows where Δ x n = x n – x̅ n , Δ y n = y n – y̅ n , and Δ z n = z n – z̅ n .…”