U.S. forces recently destroyed six Iraqi GPS jamming systems that Iraq was using to disrupt enemy satellite positioning equipment.
The Global Positioning System was designed in 1978 by the U.S. Department of Defense as a civilian and military system primarily designed to enhance the effectiveness of U.S. and allied military forces.
During the arms race between the United States and the Soviet Union, the ability to target and hit enemy missiles was significant to the balance of power. Knowledge of the exact location of the launching station was crucial for this purpose. Since much nuclear armory was carried on submarines, it was important to be able to locate these weapons above ground or under water.
GPS was the answer.
The GPS constellation consists of 24 satellites that orbit the earth every 12 hours. Five stations -- located in Hawaii, Ascension Island in the South Atlantic, Diego Garcia in the Indian Ocean, Kwajalein Atoll in the Pacific and Colorado Springs, Colo. -- monitor these satellites.
Any place on Earth is within range of three of these satellites. The GPS receiver calculates the distance of an object from the satellites by analyzing high-frequency radio signals from the satellites.
Here's how it works: The satellite transmits a long digital pattern, known as pseudo-random code, to the receiver. At the same time, the receiver sends itself the same pattern.
Because of the distance between the satellite and the receiver, the signal of the satellite will lag behind that of the receiver.
The receiver then multiplies this time lag by the speed of light to determine the distance between the satellite and the receiver.
Since each code transmitted by the satellite is random, it is impossible for an enemy to jam it in an attempt to keep the location of an object disclosed.
In its military capacity, GPS plays an important role in times of international strife.
"There were some articles at the time of the Afghanistan War, with the idea that the Department of Defense might actually turn off the GPS satellites visible from the Afghanistan,"Environmental Sciences Prof. John Porter said.
"I've noticed personally these few days, that my GPS unit doesn't seem to be as accurate as it used to be before 9-11," he added. In addition to military use, GPS has a wide spectrum of other applications including surveying, outdoor adventure, vehicle tracking and timing. The systems need not be expensive and are becoming popular for personal use.
"I got one that can be hooked to my laptop computer for $19," Porter said.
"As I am driving along, it'll actually talk to me to tell me directions, so I don't have to bother look at the screen."
Investment banks use GPS to ensure that all their transactions are recorded simultaneously in its worldwide offices.
In 2001, the FCC required all cellular companies to equip all new cell phones with GPS units that can pinpoint a user's location to within 300 feet.
"The 911 emergency system is all based on GPS right now," said Randy Carlson, project site manager of the Virginia Coast Reserve/Long-Term Ecological Research Program.
"When an emergency call comes in, it is not necessarily physical address that is recorded, but longitudes and latitudes with labels," he said.
Carlson uses GPS frequently in his research work. He works with differential GPS
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