Fixing "bumpy" spiral


I have a polyline which is a little “bumpy”. It goes up a spiral like way. If I unroll it (purple) you can see how it differs from a stright line. What I would like to do is to “roll back” the straight line (blue) instead of the bumpy (purple) one or fix the “noise” so I get a constant slope.

I attach the GH file. Please let me know if something isn’t clear.

Thanks in advance! (15.9 KB)