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Geocaching – The Technology Behind “The Hi-Tech Treasure Hunt”
by: Tonia Jordan

It all started on May 2, 2000 with the removal of selective availability by the White House. (Selective Availability is the intentional modification of GPS signal to degrade accuracy of readings) At that moment, the GPS receiver became 10 times more accurate.

GPS, or Global Positioning System is a navigational system which operates through the use of twenty-four satellites positioned around the globe in low Earth orbit. These sattelites were placed by the U.S. Department of Defense but are free for the world to use.

Each satellite above the Earth is solar-powered, with a battery back-up for times during eclipses. They send a signal that is extremely accurate, within 40 billionths of a second. GPS receivers take the signal from the satellites and use triangulation to calculate the exact location of the user, as well as speed, distance traveled, and elevation.

Triangulation works by the receiver using the signals of three or more satellites to determine location. It is a trigonometric process that identifies the position of a point using the bearings to it from two fixed points a known distance apart.

Before Selective Availability was removed, GPS units received a scrambled signal which affected their accuracy. After May 2, 2000, a new world of opportunity involving GPS opened up.

GPS units are popping up more and more these days as their particular usefulness is recognized by the general public. Many cars today offer a GPS navigational system to help guide you to your destination.

One day after the removal of selective availability, a computer consultant by the name of David Ulmer decided to test the new accuracy. He hid a container in a forest in Oregon and shared the coordinates with an online community. Within a week, several people found his container, and they started hiding their own. Thus, “Geocaching” was born.

The name of the hobby is simple enough – Geo meaning Earth and cache referring to hidden treasure. Taking part in the sport is also simple. The only tools required are the GPS unit and a love for adventure.

The seeker acquires coordinates to the hidden container through the hobby’s official website – The GPS unit points the way, with an accuracy usually within 25 meters. Once at the location, the seeker must hunt for the hidden cache which may be in a tree stump, in between rocks or even hanging in the air!

The containers may also vary in size, from small keyholders or 35 mm film canisters to large buckets or ammo cans. Each container normally contains a log book for the finder to sign and also may hold various items and trinkets available for trading. Generally the finder takes an item and leaves another item in its place.

The removal of Selective Availability allows civilian use of GPS technology, which has led to many advantages. In addition to the hobby of geocaching, GPS is also used in surveying, exploration, mapping and various location and transportation systems, among many other uses. Geocaching is just one example of how GPS technology is used by civilians today. Technology at its finest offers a plethora of applications.