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MARCO POLO IS ROLLING IN HIS GRAVE. TODAY, WITH A DEVICE THE SIZE OF A CELLULAR PHONE, JUST ABOUT ANYONE CAN DETERINE THEIR POSITION ON THE PLANET WITHIN A FEW DOZEN FEET USING THE global positioning system.
Originally developed by Rockwell International for the Department of Defense, the Navigation Signal Timing and Ranging Global Positioning System (Navstar GPS) was built in 1978. The Navstar system features a constellation of 24 satellites orbiting approximately 12,000 miles above the Earth.
Each 2,000-pound, solar-powered satellite circles the earth twice a day in a unique pattern, emitting radio signals on two different frequencies. The signals provide the satellites position and velocity within the constellation, as well as a time stamp and its identity.
How It Works
GPS functions by triangulation. Basically, the GPS unit compares the time a radio signal was sent from a satellite to the time it was intercepted by the GPS receiver. The travel time indicates the GPS units distance from the satellite. Distance is calculated by multiplying velocity (the speed of light - 186,000 miles per second) by time (the travel time of radio signal).
With distance measurements from additional satellites, the receiving unit can pinpoint a locations latitude and longitude, and the location can be displayed on the units electronic map. While three satellite ranges can provide a rough position, the system requires four satellite ranges to determine an exact position. This fourth measurement helps the GPS receivers computer compensate for timing inaccuracies and delays as the radio signals pass through the Earths atmosphere.
For around $200, GPS can be enjoyed by just about anyone. Mariners, pilots and outdoor enthusiasts rely on GPS to locate their position and guide them to even the most remote destinations. Surveyors rely on GPS to plot land masses. Even our computer clocks are calibrated using GPS radio signals, which are accurate to within a few fractions of a second.
The use of GPS in automotive navigation is perhaps its most exciting application. Imagine a dash-mounted device that provides step-by-step driving directions, right down to the estimated travel time. Low on gas? You can use GPS to find the nearest gas station. While youre at it, you can locate your favorite fast-food restaurant for a bite to eat along the way. Automotive GPS is capable of performing these tasks, as well as driver assurance services like roadside assistance, vehicle tracking, remote diagnostics and more.
Recent innovations in GPS technology include smaller, lighter designs, better reception and longer battery life. Basic models provide reliable position and navigation information, while more advanced receivers offer PC-uploading capabilities and an integrated database of cities, highways, roads, restaurants, lodging, lakes, parks, and other points of interest. Its easy to see why GPS has created such excitement in the world of navigation.
Jennifer Fischer is the former editor of Drive and is a frequent contributor to the magazine.
Drivers of select 2003 Outback models can now drive and enjoy the great outdoors with confidence, knowing they have a live OnStar advisor available to help if theyre in a major accident, experience an emergency, or have vehicle problems. The advisor can help with less-serious matters, too, such as finding a restaurant for dinner.
OnStar is the innovative in-vehicle safety, security and information service that uses the Global Positioning System (GPS) satellite network and cellular technology to link vehicle and driver to the OnStar Center, where advisors are available 24 hours a day, 365 days a year to offer real-time personalized help.
Having access to OnStar adds greatly to the confidence that comes from driving a Subaru, says T.K. Saito, Chairman and CEO of Subaru of America, Inc.
OnStar-equipped Outback vehicles will include a one-year subscription to OnStars Safe & Sound services, which offers automatic notification of air bag deployment, emergency services, remote door unlocking, roadside assistance and more. Subaru plans to expand OnStar availability to other Subaru models. Call 1-800-OnStar-7 or visit www.onstar.com for more details.