3 General information
3 General information
The satellite clocks made by Meinberg have been designed to provide extremely precise time to their users.
The clocks have been developed for applications where conventional radio clocks can´t meet the growing re-
quirements in precision. High precision available 24 hours a day around the whole world is the main feature of
the new system which receives its information from the satellites of the Global Positioning System.
The Global Positioning System (GPS) is a satellite-based radio-positioning, navigation, and time-transfer
system. It was installed by the United States Department of Defense and provides two levels of accuracy: The
Standard Positioning Service (SPS) and the Precise Positioning Service (PPS). While PPS is encrypted and
only available for authorized (military) users, SPS has been made available to the general public.
GPS is based on accurately measuring the propagation time of signals transmitted from satellites to the user´s
receiver. A nominal constellation of 24 satellites together with some active spares in six orbital planes 20,000
km over ground provides a minimum of four satellites to be in view 24 hours a day at every point of the globe.
Four satellites need to be received simultaneously if both receiver position (x, y, z) and receiver clock offset from
GPS system time must be computed. All the satellites are monitored by control stations which determine the
exact orbit parameters as well as the clock offset of the satellites´ on-board atomic clocks. These parameters
are uploaded to the satellites and become part of a navigation message which is retransmitted by the satellites
in order to pass that information to the user´s receiver.
The high precision orbit parameters of a satellite are called ephemeris parameters whereas a reduced pre-
cision subset of the ephemeris parameters is called a satellite´s almanac. While ephemeris parameters must
be evaluated to compute the receiver´s position and clock offset, almanac parameters are used to check which
satellites are in view from a given receiver position at a given time. Each satellite transmits its own set of
ephemeris parameters and almanac parameters of all existing satellites.
GPS180PEX
Date: 28th March 2018
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Содержание GPS180PEX
Страница 1: ...MANUAL GPS180PEX Satellite controlled Radio Clock 28th March 2018 Meinberg Funkuhren GmbH Co KG ...
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Страница 26: ...10 1 2 IRIG Standard Format 22 Date 28th March 2018 GPS180PEX ...
Страница 27: ...10 Technical appendix GPS180PEX 10 1 3 AFNOR Standard Format GPS180PEX Date 28th March 2018 23 ...