If your GPS device told you do drive off a cliff or ford a raging river, would you do it? You may respond, of course not, that’s stupid. Unfortunately, many people substitute technology for common sense, often with tragic results.

Satellite navigation systems are changing the way in which we navigate from place to place by land, sea or air; in remote wilderness areas or through congested urban streets. The GPS system has been called the greatest advance in outdoor navigation since the invention of the compass and has become a widely used aid to navigation worldwide, a useful tool for map-making, land surveying and recreational navigation. An estimated 50 million navigation devices, including in-car systems, handheld or portable units and smart phones, will be in use in the United States this year.

Whether you're prospecting, hunting, fishing, cross-country skiing, or taking a hike in the back country, a GPS receiver can help you reach your destination and return safely - but only if you know how to accurately use it and recognize its limitations.

The Global Positioning System (GPS) is a satellite-based navigation system made up of a complex network of more than 30 satellites placed into orbit by the U.S. Department of Defense. The GPS network, also called NAVSTAR, was originally intended for military applications, however when Korean Air Lines Flight 007 was shot down in 1983 after straying into the USSR's prohibited airspace, President Ronald Reagan issued a directive making GPS freely available for civilian use as a common good. The GPS works all the time, in any weather condition, anywhere in the world, 24 hours a day.

Powered by solar energy, the numerous satellites that make up the GPS space segment orbit at approximately 12,000 miles above the earth. Moving constantly at speeds in excess of 7,000 mph, the satellites each make two complete orbits of the earth in less than twenty-four hours. The GPS satellites are kept on track by small rocket boosters. Primarily operated on solar power, the satellites also employ backup batteries in anticipation of power loss during a solar eclipse.

The first GPS satellite was sent into orbit in 1978, with a full constellation of satellites achieved in 1994. Weighing approx-imately 2,000 pounds, each satellite is about 17 feet across with the solar panels extended and is built to last about ten years. Replacement satellites are constantly being built and then launched into orbit.

GPS signals can be affected by multi-path issues, where the radio signals reflect off surrounding terrain such as tall buildings, mountains or large obstructions. This increases the travel time of the signal and can cause inaccuracy. The number of satellites visible, or the more satellites a GPS receiver can "see" will also affect accuracy. Electronic interference, buildings, terrain or sometimes even dense foliage can block the signal reception and cause positioning errors or prevent a position reading at all.

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