Ten years ago today, President Bill Clinton gave the green light to the U.S. military to stop intentionally scrambling satellite signals, thus paving the way for civilians to use GPS with the same accuracy as the military had long enjoyed.
A decade later, mobile navigation is an indispensable part of many people's everyday lives, both in the U.S and around the globe. GPS receiver prices have dropped sharply, costing a few hundred dollars or less where they used to cost thousands. Devices have also gotten more compact and feature-rich, now routinely including access to real-time information from the Internet during route calculation--the latest traffic reports, online points of interest, and so on.
Clinton's order, which kicked into gear at 8 p.m. EDT on May 1, 2000, effectively increased the pinpoint accuracy of any consumer-grade satellite navigation receivers from around 100 yards to just 10 yards.
"President Clinton's landmark decision to open up the GPS signal in 2000 was the catalyst that triggered the launch of navigation systems as we know them today," said Johannes Angenvoort, executive vice president of Navigon, the developer of MobileNavigator for the iPhone and other smartphones, which is arguably the most comprehensive application of its kind.
A history of satellite navigation
Apart from cars, boat, airplanes and so on, satellite navigation technology is now standard in mobile phones and handheld devices, but the satellite positioning signal has been available to the U.S. military since 1960. Then, the first navigation satellite, the Transit 1B, launched into space and marked the beginning of the U.S. Navy Navigation Satellite System. This system was developed primarily to guide Navy military missiles.
This pioneering project led the U.S. Department of Defense to improve accuracy with a follow-up system, which launched in the 1980s, called the Global Positioning System (GPS) that is still in use for positioning today.
When GPS service was first made available for civilians in 1983, for national security reasons, the U.S. military decided to scramble the signal, making it a little too inaccurate to be reliable. This practice, also known as "selective availability," was aimed at preventing military use of GPS by the enemies.
President Clinton's decision to turn off the GPS interference signal in an effort to make the GPS more responsive to civil and commercial uses helped consumer-grade mobile satellite navigation finally make its breakthrough.
Some interesting facts about GPS:
- Three satellites are needed to ascertain the position of a GPS receiver.
- It takes 24 satellites and several backup satellites orbiting the Earth at a height of more than 20,000 kilometers, to ensure that three satellites are available anywhere in the world and at any time.
- Satellites transmit an uninterrupted signal detailing their current location and time, and it's up to the GPS receiver to handle the signal delay with the help of an integrated clock to calculate its own position and speed.
- Using distance measurements from three points, known as trilateration, exact positions are determined. The signal from the first satellite determines the receiver's degree of longitude; the second identifies the degree of latitude. As the receiver's integrated clock is not accurate enough to measure the exact signal delays, the clock error is calculated using a third satellite and thus identifying the exact position.
Fifty years after the launch of the first navigation satellite, there is now another known navigation satellite program called Galileo, the European counterpart to the American GPS system that's scheduled to begin operating in 2013. Galileo is a joint venture between the European Union, the European Space Agency, and various non-European countries, such as China and Saudi Arabia. The system is similar to the American GPS system, but is likely to be more accurate, with minimum deviations ranging from 4 meters to just a few centimeters.
Nonetheless, President Clinton's decision will remain a major milestone that recognized the importance of GPS to civilians and altered the landscape of the satellite navigation both in terms of usage and development. The use of GPS have been so popular that many of us, including me, take it for granted. I just can't imagine how my daily life would be without it. How about you? Share your thoughts in the comment section below.