Rusty, There are three basic types of compasses;military lensatic, orienteering and engineer's. The first two are the most commonly encountered. Your question should be " how much compass do I need for my use?" One degree of error in a mile equals 92'. Are we trying to find our way to a major landmark, or calling in an airstrike? High end compasses have luminescent dials. So, how many of us will be navigating in the dark? Will we be in snow ( avalanche) country? An inclinometer to measure angle of recline of the snowpack is invaluable. Will this compass be used in one hemisphere, or do we intend to traverse both poles? There are units designed for worldwide accuracy. When do I need a compass? If you are lost, staying put is always recommended ( unless in immenent danger or travel considered the only viable option.) Do you have a good "sense of direction", which can be learned, or have you ( like me) gotten lost in a Christmas tree lot? There are some good books; BE EXPERT WITH MAP AND COMPASS by Bjorn kjellstrom, FINDING YOUR WAY in the OUTDOORS by Robert L. Mooers,jr. and MAP READING AND LAND NAVIGATION, FM 21-26 U.S. Army