I just got done reading an article Intergrating GPS With Topographic Maps By Larry Schuh in Bowhunter MAG 2000 gear guide.
It explains basics of how a GPS works But usses Universal Transverse Mecator Projection Mode on most GPS(UTM).
Acording to the article you can find destination on a topo put the UTM in and it will put you within 20 meters.
Have you used this method and how has it worked for you?

TrestandEd

"Hard work ... conviction ... pride ... responsibility ... class ... character ... success...BOWHUNTING