design pattern to express that "container" over derived class is derived from container of a base class

I have a class Track which holds a set of Points and represent person location in time. In order to get this result I run an iterative optimization routine combining different data. In order to do it I extend Point with a class OptimizedPoint which holds data for optimization for this point and current value. I also introduce OptimizedTrack which is a collection of OptimizedPoints and additional data needed for optimization associated with the whole track.

I run an optimization on OptimizedTrack and at the last iteration, I return to the user clean data (Track) which only has the result and doesn't have additional data. However, I can not find a way to express with OOP that OptimizedTrack is somehow an extension of the Track and introduce common routines for them. F.e getting a length of the track which should be available for both of them as it only uses data which can be found both in OptimizedTrack and Track

Right now I have such architecture Point{x, y, z}, OptimizedPoint extends Point {additional_data}. Track {array<Point>}, OptimizedTrack {array<OptimizedPoint>, additional_data}. I don't understand how to express that OptimizedTrack is an extension of Track as I can not express array<OptimizedPoint> extens array<Point>. So I can not introduce a common routine length which can be calculated for array and therefore also from array.

I do not insist on my current architecture. It's most probably wrong, I only write it here to express the problem I am facing. How would you propose to refactor my architecture in this case?