In the early days of the quest for navigating around the globe, ancient travelers depended on a variety of factors like observing the direction of wind and waves in the oceans, awareness about ocean currents and weather patterns, observing birds, knowledge about stars and other celestial bodies, landmarks, and even sheer instincts to find their current location on our planet. With the invention of much more sophisticated navigational aids like magnetic compasses, nautical charts, marine chronometers, sextant and radio signals, finding one’s location on the globe became more accurate and easier.

However, it was the satellite navigation systems like GPS (Global Positioning System) – built during the latter half of twentieth century with the idea of using satellites orbiting in space for the purpose of geographical positioning – that completely revolutionized global navigation. The GPS system currently has more than thirty satellites that keep on transmitting microwave signals over specific wavelengths globally around the clock. These signals can be used by anyone with a GPS receiver to find their position on our globe. The GPS receivers pickup these signals and process the information within them to calculate accurate longitude and latitude readings along with altitude on or above the Earth’s surface.

A short history of GPS

In 1960, Transit I, the world’s first navigational satellite was launched by USA, which set the foundations of calculating Global Positioning using satellites. By 1970, the initial phases for setting up a GPS network – the plan was to cover the entire globe with an array of 24 satellites – began in earnest in the US.

The first of the original 24 NAVSTAR satellites for the GPS network was launched in February 1978 and after much refinements and enhancements to the satellites during the 80s, the system was made fully operational by 1995.

The system was designed to provide multiple signals from the array of satellites to any location on our planet to ensure precision positioning. This satellite-based navigation and location project, which was launched by the US Department of Defense for US military, was later made available for civilian use. With the advent of computers and computing systems for various navigational purposes during the 90s, the GPS became an integral part of civilian navigation across the globe. Soon aircrafts, ocean vessels, land based vehicles and even hikers were equipped with various GPS receivers, which allowed them to navigate with pinpoint accuracy.

How does GPS Work?

The main component of the GPS network is a grid of satellites that orbit the Earth twice every day at an altitude of 20,200 km (12,552 miles). These satellites transmits radio signals encoded with precise timestamps and the position of the satellite in space. An onboard atomic clock, which is highly precise is used by these satellites to generate these timestamps. Travelling at the speed of light, these signals reach Earth from space in less than a second.

In order to plot its own location on Earth, a GPS receiver has to gather signals from at least 3 or more satellites – a minimum of 4 for plotting the altitude. Each satellite signal will reach the receiver at fractionally different times, and the receiver measures the time each signal takes to arrive to calculate its precise location. From the difference between the timestamps that are received from each of these satellites, the receiver performs some complex calculations to find how far each of the satellite is and can then arrive at its own geographic co-ordinates. The receiver performs these computations in a fraction of a second and then presents the user with the location data either as raw longitude and latitude values or plots them on special navigational or mapping software.

GPS has made a huge impact in the way we humans live today. Apart from navigation, the GPS technology is used in areas like cartography, fleet tracking, tracking polar ice sheet movements, tracking tectonic activities, rescue operations, astronomy and military applications.

Other Satellite Navigation systems like GPS

Apart from GPS, GLONASS developed by Russia, BeiDou Navigation Satellite System by China, Galileo by European Union and NAVIC by India are the currently operational satellite navigation systems.