NavCom SF-2040 Rev.E - Manual (Page 46)

SF-2040 User Guide - Rev. E
Infrastructure
The system utilizes the GPS satellite system, L-Band
communication satellites, and a worldwide network of
reference stations to deliver real-time high precision
positioning.
To provide this unique service, NavCom has built a
global network of
dual-frequency reference stations,
which constantly receive signals from the GPS satellites
as they orbit the earth. Data from these reference
stations is fed to two USA Processing Centers in
Redondo Beach, California and Moline, Illinois where
they are processed to generate the differential
corrections.
From the two Processing Centers, the correction data is
fed via redundant and independent communication
links to satellite uplink stations at Laurentides in
Canada, Goonhilly in England and Auckland in New
Zealand for uplink to the geo-stationary satellites.
The key to the accuracy and convenience of the
StarFire
™ system is the source of
DGPS corrections. GPS
satellites transmit navigation data on two L-Band
frequencies. The StarFire
™ reference stations are all
equipped with geodetic-quality, dual-frequency
receivers. These reference receivers decode GPS signals
and send precise high quality dual-frequency
pseudorange and carrier phase measurements back to
the Processing Centers together with the data
messages, which all
GPS satellites broadcast.
At the Processing Centers, NavCom's proprietary
differential processing technique, developed under
license from the NASA Jet Propulsion Laboratory (
JPL )
based upon the JPL Real Time Gypsy ( RTG ) software, is
used to generate real time precise orbits and clock
correction data for each satellite in the
GPS
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