Do I really need to build my own CRS for this? If so how?

[awa5114]

Note: cross-posting from here

I have a set of polylines which are described by a project-specific, local coordinate system. I would like to find a more or less accurate way of reprojecting these polylines to EPSG:28992. I have been looking into building my own custom projection with pyproj but it looks like this is quite complicated.

I'd rather have an easier way. However, if there isn't, would anyone give me some pointers on how to start building my own coordinate system such that I can reproject my locally defined polylines to an EPSG based coordinate system like EPSG:28992?

Thanks