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Chapter 2 - Installation
Position Location
When extracting data from the Global Positioning System, there are four
unknown variables which the GPS receiver must resolve: X position, Y
position, Z position, and time. Each of these variables has an effect on
the other. Therefore, before the GPS Receiver can produce an accurate
time output, it must first obtain valid data for the other three values.
Automatic Position Location
When the system is installed and powered for the first time, the GPS
Receiver will automatically proceed to obtain an accurate position fix
(unless it receives instructions to the contrary).
The position fix is performed with the knowledge that there is no user
motion. When the position is established, the solution is frozen in
positional terms and all measurements are diverted to time and
frequency states.
Automatic sequence:Search the sky to lock-on to satellites, and download almanac data
for all other remaining satellites.
Calculate a position, and perform checks to ensure the solution is
accurate.
Change the frequency of the oscillator so that it matches the timing
information received from the GPS satellites.
If position matches, enter time transfer mode with stored position. If
position does not match, enter averaging mode.
When the timing and frequency outputs are within specification,
enable the outputs, illuminate the Green LED.
Average the position data when an accurate position is determined,
Store this surveyed position in memory for future use.
This automatically derived position will be of sufficient accuracy to
enable output of a timing solution. Calculated position being within the
specifications of the GPS Receiver system, and of an accuracy superior
to most maps.
NOTE
Should the installation subsequently suffer an interruption to the power supply, the
Alvarion-GPS Receiver re-initializes itself utilizing the Surveyed Position
.
GPS Timing Receiver Installation and Operation Manual
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