The Global Positioning System (abbr. GPS) is a satellite-based navigation system, which was developed by the United States Department of Defense. Originally developed for military use, it was made available for the general public in the 1980s.
It is operated with the help of 24 satellites placed in the orbit, which are programmed to work 24 hours a day, in any weather, and in any part of the world. These 24 satellites circle the Earth twice a day, and transmit signal information to the planet.
GPS receivers located on the Earth use triangulation―a trigonometric method of determining position―to ascertain the user's exact location. In this process, the time taken for the signal to be transmitted and the time taken to receive the signal is calculated.
After analyzing the time taken, with the distance measurement from a few more satellites, the user's position is displayed on an electronic map. A GPS receiver needs to be locked with the signal of at least 3 satellites to obtain a 2D position, and 4 or more satellites to obtain a 3D position. It can also calculate speed, distance, and time.
History of Global Positioning System (GPS)
The Global Positioning System was built by the U.S. Department of Defense in collaboration with the Massachusetts Institute of Technology (MIT). In 1951, the U.S. Air Force wanted a guidance system for the proposed ICBM that was to travel by railroad.
In order to cater to this need, American physicist and electrical engineer, Dr. Ivan Getting developed a 3D positioning system which could determine location based on time difference of arrival. This system eventually became the platform for the Global Positioning System or GPS we use in our daily lives.
The decision to develop an advanced satellite navigation system based on the existing technology of the U.S. Air Force and the U.S. Navy, gave rise to the GPS in 1973. It went through extensive testing for the next few years.
Although, the satellites were yet to be launched, the first transmitters were installed, and successfully tested with the help of Pseudolites (or pseudo-satellites) in 1977. Eventually, by 1985, eleven satellites were launched into space.
The first Block I satellite with special sensors to detect atomic explosions was launched by the United States in 1980 to monitor the Soviet Union's compliance to refrain from nuclear testing. Same year, the on-board atomic clocks, accurate to one-billionth of a second were activated. These clocks measured time with change in the energy levels of electrons.
Initially developed for the military, GPS was made available for public use in 1983. The Korean Airline Flight 007 tragedy, in which Soviet fighters shot down a Korean civilian aircraft lost over Soviet territory, led to the removal of security classifications by then U.S. President Ronald Reagan, thus allowing the general public to use it.
In 1986, the Challenger Space Shuttle Tragedy further delayed development in GPS, as the shuttles which were to transport Block II satellites were temporarily suspended. Eventually, in 1989, 28 satellites were launched for better functionality.
In 1990, the GPS facility for public use was temporarily suspended, as the military needed more receivers to enhance its use for military purposes in the Gulf War. It was made available for public use in 1993. Simultaneously, it was decided to provide this facility free of cost all over the world.
By 1995, it had become a considerably advanced navigation system. It had achieved 'Full Operational Capacity' and the number of satellites had also increased, thereby increasing the availability and accuracy of the technology.
In July, 1997, 12 satellites in the series Block IIR were succesfully launched proceeding the failure of the same in January 1997; most satellites had an experimental payload for rescue and search, namely ‘Distress Relating Satellite System.’ In 2005, IIR-M series was launched and it carried a military signal, ‘L2C’ which was a more powerful civil signal.
‘Follow-on’, IIF Block satellite series was first launched in May 2010 and its final series was launched in February 2016. With some technological advancements, first series of the third-generation GPS satellites, ‘Block III A’ series was launched in December 2018.
Previously having a capacity to track a subject within 100 m, today, this tracking range has advanced and come down to one meter (and even a few centimeters in some cases). Used exclusively by military establishments at one point of time, real-time GPS tracking has become an important component in fields like aviation, navigation, and land surveying today.
GPS tracking devices have suddenly become the most sought-after gadgets, such that GPS-integrated car navigation systems assist drivers to keep a track of routes, while cell phones and watches with integrated GPS help parents keep an eye on their children.