Given a surface in 3-space or scattered points from a surface, we inve
stigate the problem of deciding whether the data may be fitted well by
a cylindrical surface, a surface of revolution or a helical surface.
Furthermore, we show how to compute an approximating surface and put s
pecial emphasis to basic shapes used in computer aided design. The alg
orithms apply methods of line geometry to the set of surface normals i
n combination with techniques of numerical approximation. The presente
d results possess applications in reverse engineering and computer aid
ed manufacturing.