Adrian,
I am once again struggling?!! I am running into the same problem, I have set the map to the DATAM you suggested, I built some features in another map, trying to bring them over to measure and add points to a line. I define the projection to the MAP, but the feature, instead of being in Park City is either in Texas, Mexico or California?
In the orgininal map when I ran the calculate geometry it came out to 26.9 miles, which seems accurate, When I try to create points on a line, it says its 35 miles. So i came back, tried to recreate the process from above but no love...
At a total loss...