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9.10.3.1 Structure of the system
The system consists of three segments:
- Space segment
- Ground segment
- User segment
The space segment
The space segment
consists of satellites.
The operational system
operates with 24 satellites divided into 6 orbits with 4 satellites in each orbit. In
addition, there are spare satellites. The satellites are in orbit approximately
20,200 km above the Earth's surface.
The satellites each receive their positions updated from the Master Control
Station, which receives information from monitoring antennas located around
the globe.
Each satellite constantly transmits a Navigation Message, which contains
information about the individual satellite and the constellation of satellites. This
is done in the form of an almanac and an ephemeris.
The almanac provides information about orbit data for all satellites. Almanac
data is not very precise, and it can be valid for several months.
Almanac data takes a long time to download for a GPS receiver.
Ephemeris data is very precise data from each individual satellite regarding its
position and the exact time of transmission. This data is transmitted every 30
seconds.
Flyveteori PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 896
