Global Positioning System
ewis and Clark tested Indian data by astronomical and other readings obtained under conditions that would defeat most of us today: heat, cold, wet, dry, darkness, hunger. It often took three or four men to complete the necessary mechanical operations necessary to get even a moderately accurate figure for the elevation of the sun or moon above the horizon and the end results of their calculations were, by modern standards, not very good.
Today, someone with but a few minutes of training can use a hand-held GPS (Global Positioning System) device to download latitude and longitude information from an orbiting satellite, link that information to a portable computer that will show a map locating the coordinate position of the observer, accurate to within a few meters. And the cost of the modern equipment (including the computer), in 1804 dollars, is only a small fraction of the money spent by Lewis on his "mathematical instruments."
Since we already have reliable maps, identifying a location precisely on the landscape for us is merely a convenience that helps us find our way to a new and unfamiliar place. The handheld GPS device is to us, quite simply, a toy. For Lewis and Clark, who paid an enormous sum for a somewhat reliable watch, such a device would have been priceless.
--John Logan Allen