GPS - Global Positioning System (How It Works, System, History & Applications, Common Use)

The full form of GPS is Global Positioning System (ग्लोबल पोजिशनिंग सिस्टम). It is a satellite-based navigation network used to find and track locations. The most common example being google maps which helps you find the exact location of a particular place. It is an American owned satellite system that offers free global positioning, navigation and timing services. Its core constellation uses 24 satellites in 6 orbital planes which is about 20,200 kms above Earth. The satellite orbits the Earth twice in a day. Each satellite carries an atomic clock which is accurate to nanoseconds.

The GPS determines an individual's location by using multiple satellites and the technique known as Trilateration. The GPS satellites continuously orbits the Earth and relays radio signals. To calculate accurate location minimum 4 satellites are used. A single satellite covers the perimeter of around 20,000 kilometres using the intersection points of 2 satellites. A location can still be tracked but a 3rd satellite is used to accurately track the location and to avoid errors.

GPS is like a network of satellites and your smartphone device receives the signals from a minimum of 4 satellites. It measures the time of the signal to reach the receiver and calculates your distance from each of the 4 satellites. By simply using the distances, the exact location is determined where all the measurements meet which is 'your location'. This method is known as 'Trilateration' and provides latitude, longitude, altitude and time. The 4th satellite provides the timing , altitude and removes the clock error of the receiver.

The GPS works in all weather and 24/7 but requires the signal from a minimum of 4 satellites to measure latitude, longitude, altitude and time. GPS is useful for navigation, mapping, agriculture, transportation, disaster response and precise timing for communication. The GPS services are free of cost for the users.

• Military Origin: It was originally named as NAVSTAR GPS and developed by the US department of defence in 1973. It improved the limitations of previous navigation systems.
• First Launch: The first operational satellite of GPS was launched in 1978 and it became a full constellation of 24 active satellites in 1993.
• Access to Civilian: The use of GPS by the general public was approved in 1983 after the downing of Korean Air Lines Flight 007. However, full high accuracy access was granted in 2000.
• Modern Features: The latest technology has introduced dual frequency signals, improved accuracy, faster signal receiving, and integration of modern smartphones and autonomous systems.

• Global Coverage: It operates across the world and provides the uninterrupted positioning, velocity, and timing services irrespective of local weather conditions.
• Satellite Network: A minimum of 24 active satellites revolves around the Earth two times daily at an altitude of about 20,200 kilometres. The satellites are placed in such a way that at any time at least 4 satellites are visible from any point on Earth.

• Principle of Trilateration: It tells the exact location including latitude, longitude, and altitude. It calculates the distances from 4 different satellites.
• Time Synchronization: It is dependent on the atomic clock which is placed in satellites. It measures the travel time of a signal and enables the millimeter level positioning accuracy for advanced applications.

• 3 important segments: It operates through 3 synchronized components: Satellite (Space segment), ground stations monitoring orbits (Control Segment), and receiver in phones, vehicles, and aircrafts (user segment).
• Signal Integration: The radio signals from space are continuously processed by the receiving stations. They provide coordinates, speed, and real time directions across the world.