Hello all I work in railway transport. I am trying to re-design an existing railway curve; the existing curvature has several irregularities which result in the train being laterally displaced as it traverses the curve. What I have done is taken x,y and z co-ordinates along the railway curve and named each point A, B C … and so on. Using this data I want to re-design the curve so that the irregularities of the curve are removed, the only restriction I have is that I am only allowed to move the curve, at a particular point, tangent to the curve at that point. Attached is a basic diagram of I am referring to. • The red dots represent the points along the curve I have taken x y z co-ordinates. • The blue line represents the tangent line at that point. • The arrow which is 90 degrees to the tangent line represents the directions which the curve at that point can be moved to. Can anybody shed any light on how I can manipulate the co-ordinates such that I can smooth out the curve but making sure that any movement is tangential. Thank you or your help.