Basic Global Positioning System (GPS) Overview

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By: Ken Dennis
The Global Positioning System, or GPS is a constellation of twenty four (24) active satellites and three (3) additional backup satellites. The GPS system was developed and implemented by the United States Air Force (USAF) for operational reasons, and has since become world wide phenomenon, used by hikers, outdoors men, and a vast array of commercial uses.

GPS works on the principles of Triangulation. Satellites send signals down to the earth, which are triangulated by the GPS receiver unit giving you your current location. In order to acquire your current location a receiver unit requires at least three satellite signals to extrapolate your location, though more is desirable. It is not uncommon to have your receiver pickup four to seven signals in any given location. (continued...)

The GPS Satellites send out two signals: 1575.42 MHz - The Course Acquisition Signal (CA) 1227.6 MHz - Precision Signal (P)

All users, military or civilian are allowed to use the Course Acquisition signal, however the Precision signal is only used by the military, and gives much greater accuracy. The signals are closely monitored and audited by several stations, however the master station for GPS is located in Colorado Springs, USA, at Falcon Air Force Base (AFB).

Problems with the GPS System: Unfortunately due to the very low signal strength (around -127 dBm) GPS receiver units are often unable to acquire a good signal if you are in an area of dense foliage or under a heavy tree canopy. The GPS signal is also unable to penetrate most solid items, and requires a view of the sky to be effective. Use in deep canyons, or inside large cities with tall buildings will cause reduced satellite acquisitions and thus less accuracy or no triangulation at all.

Since GPS receivers have become so mainstream people seem to have thrown away the map and compass which could be a dangerous mistake. GPS receivers are an electronic unit and have the potential to fail, cold climates, batteries, dropping it could leave you lost. A GPS is a wonderful tool, however it shouldn't be a replacement for the old map and compass.

Fun and Games: There are a lot of great uses for GPS receivers, from marking your favorite fishing spot, to GeoCaching! A standard GPS receiver is between 100-250 dollars and can be used to give you your speed, average speed, set waypoints (mark your favorite spots), record tracks where you have been and can be loaded maps of different regions around the world. They are a great tool for hikers, campers, and outdoor enthusiasts and can help foster a healthy outdoor activity for you and your family.



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