The importance of precision for GPS tracker
The GPS is a constellation of twenty-four satellites (plus spares) that orbit the earth every twelve hours at an altitude of 14,000 miles from the earth's center. The system is owned and operated by the DOD, specifically the Air Force. Each satellite carries four highly accurate atomic clocks that "tick" to an accuracy of 1 nanosecond (one-billionth of a second); future satellites are expected to be accurate to between .01 and .1 nanosecond. The satellites broadcast their precisely timed radio signals through the atmosphere and onto the earth's surface at the speed oflight. The signals from each satellite arrive at any particular point on or above the earth's surface at slightly different times. GPS receivers passively calculate where they are and what time it is by comparing the signals of multiple satellites in the constellation. Receivers require an unobstructed view of the sky, so they can be used only outdoors, and they often do not perform well in forested areas or near tall buildings.
The degree of accuracy of tracking device signals varies. Initially, timing errors were deliberately inserted into the transmissions to downgrade the accuracy of nonmilitary GPS receivers. This practice, called selective availability (SA), was intended to discourage foreign military exploitation, but the argument was overtaken by another technology, differential GPS (DGPS), which could circumvent SA through an additional receiver fixed at a known location nearby. Observations made by the stationary receiver correct positions recorded by the mobile units, producing an accuracy ofabout 1 meter. The SA "switch" was subsequently turned off by President Clinton in May 2000. Now, the accuracy of a GPS-determined position depends on the type of receiver being used-Most handheld electronic tracker , widely available in retail stores and on the Internet for upward of $100, have about lO-meter accuracy. Military receivers, in addition, use the encrypted so-called P-code-precise or precision code-to increase accuracy.
The importance of precision for GPS, especially when used with other satellite systems, cannot be overstated. Responsibility for the GPS satellite constellation belongs to the Second Space Operations Squadron at Schriever Air Force Base, Colorado. In 1996, a timing error was transmitted from the GPS control center to one GPS satellite for six seconds before being caught by an alert operator. Over 100 commercial cell-phone networks on the East Coast were affected, some for up to twenty-four hours. This illustrates how important the program has become in a very short time, despite having no clearly defined mission at conception, and its significant financial implications. It also explains why the GPS has become known as one of the first global utilities.
The experience of just one company shows how lucrative GPS-related business has become. In 2003, Forbes added Garmin International co-founders Gary Burrell and Min Gao to its list of the 400 Richest People. Burrell and Gao founded a company, initially called ProNav, in 1989. In 1990, they introduced the GPS 100 Personal Navigator, a $2,500 boating navigation aid. The company's first customer was the U.S. Army during the Gulf War in 1991-another illustration of the benefit to the military of dual-use technology developed in the private sector. In 2003, after the company had expanded its product line by adding a series of tracking devices for people, such as those designed for recreational runners, and integrated PDA-GPS receivers, the market value of the company stock was estimated at $4.5 billion, with $465 million in annual revenue and $142 million in profits. It should be no surprise that investors worldwide are interested in this technological gold mine.
The degree of accuracy of tracking device signals varies. Initially, timing errors were deliberately inserted into the transmissions to downgrade the accuracy of nonmilitary GPS receivers. This practice, called selective availability (SA), was intended to discourage foreign military exploitation, but the argument was overtaken by another technology, differential GPS (DGPS), which could circumvent SA through an additional receiver fixed at a known location nearby. Observations made by the stationary receiver correct positions recorded by the mobile units, producing an accuracy ofabout 1 meter. The SA "switch" was subsequently turned off by President Clinton in May 2000. Now, the accuracy of a GPS-determined position depends on the type of receiver being used-Most handheld electronic tracker , widely available in retail stores and on the Internet for upward of $100, have about lO-meter accuracy. Military receivers, in addition, use the encrypted so-called P-code-precise or precision code-to increase accuracy.
The importance of precision for GPS, especially when used with other satellite systems, cannot be overstated. Responsibility for the GPS satellite constellation belongs to the Second Space Operations Squadron at Schriever Air Force Base, Colorado. In 1996, a timing error was transmitted from the GPS control center to one GPS satellite for six seconds before being caught by an alert operator. Over 100 commercial cell-phone networks on the East Coast were affected, some for up to twenty-four hours. This illustrates how important the program has become in a very short time, despite having no clearly defined mission at conception, and its significant financial implications. It also explains why the GPS has become known as one of the first global utilities.
The experience of just one company shows how lucrative GPS-related business has become. In 2003, Forbes added Garmin International co-founders Gary Burrell and Min Gao to its list of the 400 Richest People. Burrell and Gao founded a company, initially called ProNav, in 1989. In 1990, they introduced the GPS 100 Personal Navigator, a $2,500 boating navigation aid. The company's first customer was the U.S. Army during the Gulf War in 1991-another illustration of the benefit to the military of dual-use technology developed in the private sector. In 2003, after the company had expanded its product line by adding a series of tracking devices for people, such as those designed for recreational runners, and integrated PDA-GPS receivers, the market value of the company stock was estimated at $4.5 billion, with $465 million in annual revenue and $142 million in profits. It should be no surprise that investors worldwide are interested in this technological gold mine.
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