Carly,
Over on Cybergolf, I did a series of articles on the development of The Quarry at Giant's Ridge in the architects corner section. By the way, they should have the grow in photos posted now, so any who are interested can see how it came out!
One installment (God help me, I can't recall which, so you'll have to skim the whole thing) dealt with our contractor's use of GPS to stake out the golf course. It was a big help, as they could use one man instead of two, and he could stake it out by walking around for an hour. In many cases, he staked while we were at lunch and we came back to find we could modify the plan in the field to save earthmoving, key trees, etc.
The key was our computer drawn plans, the existing topo maps, proposed topo maps, and the actual ground topo could all be compared to see what the plans problems were instantly.
I also have consultants using GPS to map as constructed projects better than ever before.
As far as assessing ground forms for design before hand, I know there is new LIDAR technolgy, which is mapping with radar rather than stereo aerial photos. Some low tech devices - like eyeballs - still work pretty well, too!