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GPS segments

GPS segments

The GPS system consists of three segments:

  1. The space segment, consisting of 24 or more satellites, with accurate atomic clocks on board, continuously transmitting ranging signals to Earth.
  2. The control segment, consisting of a number of ground stations, which monitors the satellites, computes their orbits and clock offsets, and uploads this information to the satellites, which in turn encode this information on the ranging signal (the so-­called navigation data).
  3. The user segment, simply consisting of many GPS receivers, which each track four or more GPS satellites, and compute their own position.

GPS segments
Figure 1: GPS segments

GNSS orbital planes are inclined with respect to the equator (at 55° for GPS). All the satellites form a constellation.