I measured an XC course a couple of years ago. I made detailed notes of every turn and documented every turn point and timing point with GPS coordinates. I created a good map for the client and I enclosed the documentation with the map.
Since then, most if all the races held on this 5K course have been held on the same path with the exception of the out and back segment I added to the old course to make it as close to 5K as possible. No one liked having to run that extra piece of ~ 200 yards. Of course, this has never stopped all the races there from being advertised as "5K".