I think i see a Catia User :-)
( Catia users seems to like the "Join curves" feature, which is not really necessary in NX.)
Is the input to the uploaded example, the points, data from a FEM system ?
The points used does not produce smooth curves,
have a look at the image, there is a noticeable bump around pp54.
These curves are what i would call "overloaded", There is too much data, too many points used to create these relatively simple curves. The result is splines with undulations due to that the points do not lie on the perfect curve.
the curvature comb flickers back and forth.
The splines , the convex side , is a degree 3 spline with 34 segments, -there are 34 "sub-equations" used to describe the convex side. this is too much data for that shape. That curve will produce heavy and complex surfaces, difficult for subsequent operations.
Instead try match maybe a degree 4 or 5 , single segment curve to the "convex points". Use the fit curve, ( Fit curve is not a sketcher command.)
Since the points doesn't lie on the "perfect curve" you must accept deviations from the points.
Back to the original question :-)
In Drafting, search for "Simplify curve" in the command finder, then right click the view to be dimensioned, Expand.
then select the splines , the simplify curve will approximate the spline with arcs that can be dimensioned tangent-tangent. After simplification, right click the view again to turn off "expand mode".
Well, you are right about Catia
Upload example is imported .dwg,and yes your curve analysis clearly shows that some control points are unnecessary,but that didn't bothered me that much I just need overall dimensions.
Thanks for great analysis and help.
Just in case anyone needs to find overall dimension,I found this very handy tool while you are in the Drafting application, select Analysis > Advanced Mass Properties > Area using Curves it has option for position of the circle and size that gives max dim.