GPS

The Global Positioning System:-

Professor Richard Langley of the University of New Brunswick (also GPS World Innovation editor) has done several analyses to see how the use of GLONASS satellites could help compensate for a potential reduction in the number of available GPS satellites. These studies came in response to a warning from the U.S. Government Accountability Office about the potential drop in the number of healthy satellites in the GPS constellation as a result of delays in both the Block IIF and Block III modernization programs.

The GPS is made up of three parts: satellites orbiting the Earth; control and monitoring stations on Earth; and the GPS receivers owned by users. GPS satellites broadcast signals from space that are picked up and identified by GPS receivers. Each GPS receiver then provides three-dimensional location (latitude, longitude, and altitude) plus the time.


WORKING PRINCIPLE:-


Individuals may purchase GPS handsets that are readily available through commercial retailers. Equipped with these GPS receivers, users can accurately locate where they are and easily navigate to where they want to go, whether walking, driving, flying, or boating. GPS has become a mainstay of transportation systems worldwide, providing navigation for aviation, ground, and maritime operations. Disaster relief and emergency services depend upon GPS for location and timing capabilities in their life-saving missions. Everyday activities such as banking, mobile phone operations, and even the control of power grids, are facilitated by the accurate timing provided by GPS. Farmers, surveyors, geologists and countless others perform their work more efficiently, safely, economically, and accurately using the free and open GPS signals.

The Global Positioning System, usually called GPS (the US military refers to it as NAVSTAR), is an intermediate circular orbit (ICO) satellite navigation system used for determining one's precise location and providing a highly accurate time reference almost anywhere on Earth or in Earth orbit.

The first of 24 satellites that form the current GPS constellation (Block II) was placed into orbit on February 14, 1989. The 50th GPS satellite since the beginning in 1978 was launched March 21, 2004 aboard a Delta II rocket
GPS ELEMENTS:-



GPS was designed as a system of radio navigation that utilizes "ranging" -- the measurement of distances to several satellites -- for determining location on ground, sea, or in the air. The system basically works by using radio frequencies for the broadcast of satellite positions and time. With an antenna and receiver a user can access these radio signals and process the information contained within to determine the "range", or distance, to the satellites. Such distances represent the radius of an imaginary sphere surrounding each satellite. With four or more known satellite positions the users' processor can determine a single intersection of these spheres and thus the positions of the receiver . The system is generally comprised of three segments:
1. The space segment
2. The control segment
3. The user segment