The Global Positioning System (GPS) is a constellation of
navigation satellites called Navigation Satellite Timing And
Ranging (NAVSTAR), maintained by the U.S. Department of Defense.
Many outdoor enthusiasts recognize that a handheld GPS receiver
can be an accurate tool for determining their location on the
terrain. The GPS receiver helps determine locations on the
Earth's surface by collecting signals from three or more
satellites through a process called triangulation. Identifying a
location on the Earth is more useful if you also know about the
surrounding topographic conditions. Using a topographic map with
the GPS receiver provides important information about features
of the surrounding terrain and can help you plot an effective
route from one location to another. When using a topographic map
with a GPS receiver, you need to ensure that the receiver has
been programmed correctly to account for variables such as the
map datum, coordinate system, and units of measure. Refer to the
instructions that accomp