Technology

Orbiting above the earth are 24 satellites (21 active, 3 spare) that provide global positing information to those on land.  These satellites were originally put in place for military use.  In 2006, public access to these satellites was enabled.

Each of these satellites beams information down to earth.  Through the combination of signals from multiple satellites an accurate position can be calculated.

A handheld electronics device called a GPS unit is used to receive these signals and calculate your current location.  To calculate location, signals from a minimum of 3 satellites is required.  The more satellite signals your unit receives, the greater the accuracy of location reported.  Some GPS units can also report your current altitude if enough satellites are being received.

The accuracy of your GPS unit can also be affected by

• Lines of sight - objects between you and the satellite such as trees, buildings, mountains, clouds, etc..
• Weather - rain or snow may affect satellite signals

GPS units can than show your location on their electronic screen along with maps that are stored on the unit.  Topographical maps showing elevation contours, streets, and public points of interest are options on most units today.  These are extremely useful for geocaching.