C-Nav 2050, User Manual

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2050 User Guide
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, a global network of dual-frequency reference stations , which
constantly receive signals from the GPS satellites as they orbit the earth are in operation.
Data from these reference stations is fed to two Network Processing Hubs / Centers located
in Torrance, California and Moline, Illinois where they are processed to generate the
differential corrections.
From the two Network Processing Hubs / 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
communication satellites.
The key to the accuracy and convenience of the StarFire

system is the source of GPS
corrections. GPS satellites transmit navigation data on two L-Band frequencies. The
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 Network Processing Hubs /
Centers together with the data messages, which all GPS satellites broadcast.
At the Network Processing Hubs / Centers, NavCom's proprietary differential processing
techniques used to generate real time precise orbits and clock correction data for each
satellite in the
GPS constellation. This proprietary Wide Area DGPS ( WADGPS ) algorithm is
optimized for a dual-frequency system in which dual-frequency ionospheric measurements
are available at both the reference receivers and the user receivers. It is the use of dual-
frequency receivers at both the reference stations and the user equipment together with the
advanced processing algorithms, which makes the exceptional accuracy of the system
possible.
Creating the corrections is just the first part. From our two Network Processing Hubs /
Centers, the differential corrections are then sent to the Land Earth Station (
LES ) for uplink
to L-Band communications satellites. The uplink sites for the network are equipped with
NavCom-built modulation equipment, which interfaces to the satellite system transmitter and
uplinks the correction data stream to the satellite that broadcasts it over the coverage area.
Each
L-Band satellite covers more than a third of the earth.
Users equipped with a C-Nav precision GPS receiver actually have two receivers in a single
package, a GPS receiver and an L-Band communications receiver, both designed by
NavCom for this system. The GPS receiver tracks all the satellites in view and makes
pseudorange measurements to the GPS satellites. Simultaneously, the L-Band receiver
receives the correction messages broadcast via the L-Band satellite. When the corrections
are applied to the GPS measurements, a position measurement of unprecedented real time
accuracy is produced.
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