Amazing Kids! Magazine

Sci-Tech Kids! – GPS Systems for Navigating Your Adventure

by Brad Bradshaw, Sci-Tech Kids! Editor

In the 15th and 16th centuries, great explorers like Christopher Columbus faced a huge dilemma. They were traveling in totally unfamiliar land. How could these people know where they were going or how far they had gone? Back then, there were two methods of navigation: map and compass and star. As is familiar to outdoorsmen and soldiers, the map and compass method of navigation relies on the red needle of a compass pointing to magnetic north of the earth, which ranges from 8 to 15 degrees from true north. The star method of navigation, used mainly by sailors, uses an instrument called an astrolabe to determine the angle from the horizon to the north star, which is then used to determine one’s location. These two practices remained the primary methods of navigation for over four hundred years. However, in 1973 the United States Department of Defense revealed a new technology, called the Global Position System (GPS).

Personal GPS System

The GPS system was originally created as a military technology for use in tracking and firing long range missiles. However, the system also has numerous civilian uses. Let’s take a closer look at how it all works.

The “system” part of GPS describes a group of 36 satellites that orbit the earth. They are arranged in two circles, so that, from any point on Earth, one can spot at least two of them. These satellites both receive and transmit radio signals and function on a unique bandwidth (so they don’t get confused with the actual radio!) So how do these satellites know where you are?

The science backing GPS technology is pretty complicated, but it’s based on something you may be familiar with: the Doppler Effect. The Doppler Effect states that the frequency of waves emitted by an object moving toward you will increase, while the frequency of such a wave decreases when the object moves away from you. Let me explain this with an example. Let’s say you are standing on a sidewalk and a school bus is driving on the road toward you. The noise of the bus’ engine would increase as it got nearer toward you. The sound also goes up in pitch slightly. Then, as the bus passes you, the noise it makes will become quieter and deeper. This is the Doppler Effect in action! Any device that uses GPS sends out radio waves to GPS satellites. These satellites interpret the frequency of the radio wave to determine how far away you are. When at least two, and usually three of these satellites has calculated your distance, they transmit a signal back to your GPS with your exact location.

There’s a second very cool use for GPS favored by backpackers and hikers. Not only can GPS satellites find your location, they can also determine your altitude. For anyone climbing a mountain, this figure is very important. To find your altitude, four GPS satellites must receive your signal. They can then find how far you are from sea level (an altitude of 0 meters) in a process called triangulation.

What started off as a military technology for guiding long-range missiles has become a far-reaching tool with numerous applications. People use GPS every day from driving their cars to making phone calls. GPS units in phones are used in emergencies by 911 operators to send police or fire rescue crews to your location. Some dog collars have GPS units in them so that you can find your pet if he runs away.

Some people have even turned GPS navigation into a sport! Geocaching is a fun activity that combines hiking and a treasure hunt. You can download the coordinates of a “geocache” on your GPS unit, then hike to it to find treasure! There are such caches all over the world and the prizes range from candy to small toys. Check out more information on the sport at www.geocaching.com

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