GPS devices : history
The history of GPS devices and navigation in general is an interesting one. Many centuries ago, sea voyages were the primary means by which to travel between continents. Until the development of the compass and the chronometer, time and astrology were the only means to determine position and navigate across the seven seas.
Today, pilots, sailors and other travelers still use time and the heavens to find their way across the globe. These days however, time is accurate to within the millisecond and the constellations used to determine position are not constellations of stars, but rather constellations of satellites. GPS technology has transformed navigation in the heavens, on the water and on land.
GPS units were originally created for use by the military. The launch of the Russian satellite Sputnik in the late 1950s saw dream of a man made navigational star becoming apparent. The onset of the cold war saw the United States Department of Defense searching for a way to improve Russian technology. In the mid 1960s, the Transit System was used to submarines to navigate beneath the water. The system operated by measuring the radio emissions from six satellites orbiting the earth. It wasn't until 1973 however that the concept of Global Positioning was actually envisaged by the Defense Department. Official testing of satellites began in 1977and by1978 the first GPS satellite known as Block 1 had been launched. By 1979 the system was fully operational and GPS technology was a reality.
GPS remained strictly a military initiative until 1983 when a civilian flight KAL 007 was shot from the sky by Russian bomber planes. The shooting occurred due to a navigational error by the pilots of the plane who accidentally flew into Russian military airspace. The tragedy prompted the United States government under the Reagan administration to make GPS available for civilian use. Initially GPS units were used predominantly in sea and air transport circles only, but technological advances soon saw its uses being extended substantially. Today there are over 24 GPS satellites circling the earth at any given time.
The United States Department of Defense currently controls all commercial GPS transmissions. While non-military GPS systems still make use of NAVSTAR GPS satellite transmissions and operate on radio frequency known as L1, significant developments in civilian GPS navigation have occurred in recent years. These include the shutting down of Selective Availability and the use of Differential GPS to improve the accuracy of receiver readings. GPS technology is widely available in the form of handheld units, automotive navigation and GPS cellular phones to name but a few. Previously basic mapping software has advanced to the point where routes are not only exceptionally detailed, but now also three-dimensional.
The European Space Agency is currently working on a European GPS satellite program known as Galileo. This initiative has, however, been strongly contested by the American Department of Defense who claim that because it will be purely under civilian control, it will be a threat to the military. Russia has also offered the use of its GLONASS navigation satellites for civilian use, but currently there are no commercial GPS units which make use of the GLONASS transmissions. Hopefully this situation will change in the very near future, with more and more GPS manufacturers showing an interest in systems other than NAVSTAR.