Andy, Allie is correct - from my perspective (although maybe not others). You do this long enough, you get a pretty good understanding from the topo map. Couple that with years of experience marrying paper design to field construction and Wholla!
It also depends on the process you employ to build the course. Design/Build allow a for a bit more flexibility re: ascertaining quantities, than Hard Bid. However, even with D/B, unlees you have some kind of Time & Material contract, it behooves one to iron out all the wrinkles on paper because the ground can deceive. What might appear to be a gentle slope may in fact be too great for a putting surface and you end up tearing up more area, after the fact, to recitfy the situation (and the more you tear up, the more you have to restore). Also, 'in the field' sounds romantic but remember, many times you are dealing with dense vegetation or forest, where you can't get a true view of the land until it's cleared and grubbed. This then becomes a chicken-or-egg situation when doing a routing.
Even with topo, one must field review the routing and specific green/tee/hazard locations to insure that the topo is true - especially when it comes to vegetated sited.
I use a 10:1 verticle to horizonal profile on paper (actually now my computer models this for me which save alot of time) and start with a +4' eye-line. This will show me what one would be able to see and what would be obstructed.