On the surface, there is no obvious difference between how things worked in 2017 (or older versions) compared with 2018. Over the years you may have noticed that the Location Dialog, the one that allows you use a map to locate your project did not do anything at all related to the Shared Coordinate system. All that action did was provide a way for Revit to; originally calculate sun position (and therefore shadows) more believably and more recently to allow for energy analysis estimation to be done.
Now…in Revit 2018, assuming the source DWG file is using AutoCAD’s GEO Referencing feature, it is possible for Revit to inherit this data to affect not only the Location (Sun and Energy Analysis) but also the coordinate location of the project (Shared Coordinates).
The thread…