A TECHNICAL SEMINAR ONGLOBAL POSITIONING SYSTEM (GPS)
Global Positioning System (GPS) GPS is a space-based satellite navigation system that provides location and time. It is maintained by the ‘United States government’ .History: The design of GPS is based partly on similar ground-based radio navigation systems, such as LORAN and the Decca Navigator developed in the early 1940s, and used during World War II. The first satellite navigation system, used by the United States Navy, was first successfully tested in 1960. Interagency GPS Executive Board (IGEB) oversaw GPS policy matters from 1996 to 2004.
After that the National Space-Based Positioning, Navigation and Timing Executive Committee was established by presidential directive in 2004.Basic concept of GPS : A GPS receiver calculates its position by precisely timing the signals sent by GPS satellites .• the time the message was transmitted• precise orbital information.• the general system health and rough orbits of all GPS satellites.
Structure: The current GPS consists of three major segments- Space Segment (SS), Control Segment (CS), User Segment (US).Space Segment(SS)- The space segment is composed of 24 to 32 satellites in medium Earth orbit and also includes the payload adapters to the boosters required to launch them into orbit.
Control segment(CS)-The control segment is composed of- • master control station(MCS), • alternate master control station, • a host of dedicated and shared • ground antennas and • monitor stations.
User segment(US)-•The user segment is composed of hundreds of thousands of U.S. and alliedmilitary users of the secure GPS Precise Positioning Service, and tens ofmillions of civil, commercial, and scientific users of the Standard PositioningService.
Satellite frequencies:Band Frequency DescriptionL1 1575.42 MHz Coarse-acquisition (C/A) and encrypted precision.L2 1227.60 MHz military codes and newer satellites.L3 1381.05 MHz Used for nuclear detonation (NUDET) detection.L4 1379.913 MHz Being studied for additional ionospheric correctionL5 1176.45 MHz Proposed for use as a civilian safety-of- lifeDemodulation and decoding:Navigation equations:
Various Global Positioning Systems: NAVASTAR GPS – America’s Global Positioning SystemGLONASS – Russias global navigation system. Fully operationalworldwide.Galileo – a global system being developed by the European Unionand other partner countries, planned to be operational by 2014 (and fullydeployed by 2019).Beidou – Peoples Republic of Chinas regional system, currentlylimited to Asia and the West Pacific.COMPASS – Peoples Republic of Chinas global system, planned tobe operational by 2020.IRNSS – Indias regional navigation system, planned to beoperational by 2013, covering India and Northern Indian Ocean.QZSS – Japanese regional system covering Asia and Oceania.
Applications: Civilian, Restrictions on civilian use- The U.S. Government controls the export of civilian receivers. All GPS receivers capable of functioning above 18 kilometres altitude require license. Military,
Communication, The navigational signals transmitted by GPS satellites encode a variety of information. This information is encrypted encoding used by the U.S. military.Conclusion: GPS technology is playing a important in modern living.