GPS

Web tools info likes to publish articles we think would be useful to our readers. If you don't see a category that would be of interest to you, please let us know by contacting us and requesting additional categories.
if you write articles on a regular basis and would like to see them published here, please let us know and we can see about giving you your own account.

Article:

The Global Positioning System, usually called GPS (the US military refers to it as NAVSTAR), is a 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. It uses an intermediate circular orbit (ICO) satellite constellation of at least 24 satellites.

The GPS system was designed by and is controlled by the United States Department of Defense and can be used by anyone, free of charge. The GPS system is divided into three segments: space, control, and user. The space segment comprises the GPS satellite constellation. The control segment comprises ground stations around the world that are responsible for monitoring the flight paths of the GPS satellites, synchronizing the satellites' onboard atomic clocks, and uploading almanac data for transmission by the satellites. The user segment comsists of GPS receivers used for both military and civilian applications. A GPS receiver (GPSR) decodes time signal transmissions from multiple satellites and calculates its position by trilateration.

The cost of maintaining the system is approximately US$400 million per year, including the replacement of aging satellites. 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 (see article in External links section, below).