The Global Positioning System (GPS) is a space-based satellite navigation system that delivers location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites. It is maintained by the United States government and is freely accessible by anyone with a GPS receiver. The system imposes some technical limitationswhich are only removed for authorised users.
The GPS program provides critical capabilities to military, civil and commercial users around the world. In addition, GPS is the backbone for modernising the global air traffic system.
The GPS project was developed in 1973 to overcome the limitations of previous navigation systems, integrating ideas from several predecessors, including a number of classified engineering design studies from the 1960s. GPS was created and realised by the U. S. Department of Defense (DoD) and was originally run with 24 satellites. It became fully operational in 1994.
Advances in technology and new demands on the existing system have now led to efforts to modernise the GPS system and implement the next generation of GPS III satellites and Next Generation Operational Control System (OCX). Announcements from the Vice President and the White House in 1998 initiated these changes. In 2000, U. S. Congress authorized the modernisation effort, referred to as GPS III.
Other systems as well as GPS are in use or under development. The Russian GLObalNAvigation Satellite System (GLONASS) was in use by only the Russian military, until it was made fully available to civilians in 2007. There is also the planned European Union Galileo positioning system, Chinese Compass navigation system, and Indian Regional Navigational Satellite System.
A GPS receiver calculates its position by precisely timing the signals sent by GPS satellites high above the Earth. Each satellite continually transmits messages which include:
- the time the message was sent
- accurate orbital information (the ephemeris)
- the general system health and rough orbits of all GPS satellites (the almanac).
The receiver uses the messages it receives to determine the transit time of each message and computes the distance to each satellite. These distances along with the satellites’ locations are used with the possible aid of trilateration, depending on which algorithm is used, to compute the position of the receiver. This position is then displayed, perhaps with a moving map display or latitude &longitude; elevation information might be included. Many GPS units show resulting information such as direction and speed, calculated from position changes.
Contact Navman Wireless for fantastic GPS Vehicle Tracking and Fleet Management software solutions. www.navmanwireless.com.au
Navman Wireless originates from Navman, the company founded in New Zealand in 1986 which established us as a pioneer in GPS technology. Since 2001, Navman Wireless has provided GPS vehicle tracking and fleet management solutions to the transport, utility and service industries.