We assume that a lot of ancient monuments that are built for (or assumed) aligning with celestial bodies were built directly from the ground up using markers and aligning things with your eyes. Not like making a map and then charting things out.

It's easier to place a stick in the ground and mark off seasonal elongations of a star or planet's path, directly on the place you want to build it, and far more accurate that way than using a hand drawn map for reference.