Global Positioning System



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What is GPS?


A global navigation satellite system consisting of positioning
satellites and their associated ground stations

Satellites are placed in Medium Earth Orbit (MEO) at an altitude of 12,552 miles

Orbital periods of MEO satellites range from 2 - 12 hrs.

Orbital period of GPS satellites is 12 hours (2 rotations/day)

GPS Satellites travel at a speed of 7,000 mph

Orbits are arranged so that at any time, anywhere on Earth, at least four satellites are "visible" in the sky


Space Segment



GPS satellites fly in circular orbits at an altitude of 20,200 km and with a period of 12 hours.
Powered by solar cells, the satellites continuously orient themselves to point their solar panels toward the sun and their antenna toward the earth.
Orbital planes are centered on the Earth
Each planes has about 55° tilt relative to Earth's equator in order to cover the Polar Regions 


Monitor Stations


Six monitor stations are located at

Falcon Air Force Base in Colorado
Cape Canaveral
Florida, Hawaii
Ascension Island in the Atlantic Ocean
Diego Garcia Atoll in the Indian Ocean
Kwajalein Island in the South Pacific Ocean


User Segment


GPS receivers are generally composed of an antenna, tuned to the frequencies transmitted by the satellites, receiver-processors, and a highly-stable clock, commonly a crystal oscillator.

They can also include a display for showing location and speed information to the user.

A receiver is often described by its number of channels this signifies how many satellites it can monitor simultaneously