Seminar II – Global Positioning System (GPS) Presented By: 1.
Debraj Sadhukhan
2.
Kabyik Kumar Maity
Brief Description: Description: Introduction: GPS is a Global Navigation Satellite System (GNSS). It uses a constellation of 24 satellites orbiting around the earth. It transmits precise microwave signals, enabling GPS receivers to determine their location, speed, direction and time. It was first developed by United States Department of Defense whose official name is NAVSTAR-GPS. GPS satellite navigation system includes: Russian GLONASS, European Galileo positioning system, Compass navigation system of China, IRNSS of India.
Technical Description: GPS consists of three major segments: 1. Space Segment (SS) 2. Control Segment (CS) 3. User Segment (US) Space Segment: The Global Positioning System (GPS) is a satellite-based satellite-based navigation system made up of a network of 24 satellites or GPS space vehicles (SVs). There are 6 orbital planes, inclined at 55 degrees with the equator. Each plane contains 4 satellites. This constellation provides 5 to 8 SVs from any point on the earth. Orbiting at an altitude of approx. 20,200 km, satellites orbit the earth in 12 hrs and transmit signal information to earth. Control Segment: The control segment comprises of 5 stations in Hawaii, Kwajalein, Ascension Island, Diego Garcia, and Colorado Springs. They measure the distances of the overhead satellites every 1.5 seconds and send the corrected data to Master control station at Schriever Operation Squadron (SOPS) of US Air Force. Here the satellite orbit, clock performance and health of the satellite are determined and it also determines whether repositioning is required. This information is sent to the three uplink stations. User Segment: GPS receivers are composed of an antenna, tuned to the frequencies transmitted by the satellites, receiver-processors, receiver-processors, and a highly-stable clock.GPS receivers take this information and use triangulation to calculate the user's exact location. The GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position (latitude, longitude and altitude) and display it on the unit's electronic map.
Conclusion: Once the user's position has been determined, the GPS unit can calculate other information, such as speed, bearing, track, trip distance, distance to destination, sunrise and sunset time and more. It is cheap and precise operating equipment. It has Inherent error correction mode. A variant of GPS, DGPS (Differential GPS) has already been introduced which is more precise than GPS.
