How far?

One thing that really foxes me regarding distance is, how do the Pro Caddies work out the distance "left" after Tee Off, with so much accuracy, I was watching Ronan Raffatty playing three holes on an Irish course (Great Golf Journeys Setanta Golf) and his caddie is always spot on, the last one I watched on one hole his caddie said "its 91yds" not about 90 but 91. They dont seem to use any electronic help.

  � �� �I find I cant work out my distance “left” and so often use the wrong club.

Certainly do ..It's not just a case of carrying bags of clubs around. They will make as many notes as possible to aid thier actually "game on" work - bit like a shot saver with much more detail..