Finally , a method is put forward to construct the nurbs curves on sphere , which extends the de boor recursive algorithm in r3 to one on the sphere by replacing the geodesic distances for the lines and studies their many geometric properties analogous to those in euclidean spaces , such as the differential property , the local property , the parameter invariance under a projective transformation , and so on 两种方法均给出误差估计，使逼近螺线可达到任何预先给定的精确阶。最后，给出球面nurbs曲线生成算法：用球面上测地线? ?劣大圆弧代替直线段，将欧氏空间r ~ 3中的deboor递推算法推广到球面上构造曲线。
