User's Manual Part 1

Positioning Modes of Operation Chapter 5
OEMV Family Installation and Operation User Manual Rev 5B 79
Figure 24: SBAS and NovAtel 2006
SBAS is made up of a series of Reference Stations, Master Stations, Ground Uplink Stations and
Geostationary Satellites (GEOs), see Figure 25 on Page 80. The Reference Stations, which are
geographically distributed, pick up GPS satellite data and route it to the Master Stations where wide
area corrections are generated. These corrections are sent to the Ground Uplink Stations which up-link
them to the GEOs for re-transmission on the GPS L1 frequency. These GEOs transmit signals which
carry accuracy and integrity messages, and which also provide additional ranging signals for added
availability, continuity and accuracy. These GEO signals are available over a wide area and can be
received and processed by OEMV family GPS receivers with appropriate firmware. GPS user
receivers are thus able to receive SBAS data in-band and use not only differential corrections, but also
integrity, residual errors and ionospheric information for each monitored satellite.
The signal broadcast via the SBAS GEOs to the SBAS users is designed to minimize modifications to
standard GPS receivers. As such, the GPS L1 frequency (1575.42 MHz) is used, together with GPS-
type modulation - for example, a Coarse/Acquisition (C/A) pseudorandom (PRN) code. In addition,
the code phase timing is maintained close to GPS time to provide a ranging capability.
The primary functions of SBAS include:
• data collection
• determining ionospheric corrections
• determining satellite orbits
• determining satellite clock corrections
• determining satellite integrity
• independent data verification
• SBAS message broadcast and ranging
• system operations and maintenance
WAAS:
USA (1996-1999) 1st Generation
WAAS G-II Receivers
Technology Refresh (2004-2006)
Geostationary Command &
Control Segment (2004-2006)
•
•
•
•
•
148 WRS receivers
21 GUS receivers
160 WAAS G-II receivers
13 L1/L5 Signal Generators
15 L1/L5 GUS receivers
EGNOS:
Europe (2001-2002)
• 24 RIMS-C receivers
(Integrity Channel)
MSAS:
Japan
6 NLES GUS receivers
4 UPC receivers
(1998-2003)
• 47 MSAS WRS receivers
•
•
SNAS
China (2000-2002)
• 73 WAAS WRS receivers
GAGAN:
India
3 L1/L5 GUS receivers
3 L1/L5 Signal Generators
(2005)
•
•
18 WAAS-G2 receivers
•
Key
Wide Area Master
Station
Wide Area Reference
or Earth Station
EGNOS RIMS Site
SBAS and NovAtel Worldwide