1. C-Nav GPS System GPS Services Group www.cctechnol.com/cnav
C&C Technologies, Inc.,

2. The figure shows an overview of the StarFire WADGPS network
The figure shows an overview of the StarFire WADGPS network. At a conceptual level, it is similar to other wide-area DGPS systems (S.B.A.S. – Satelite Based Augmentation Systems) such as :
WAAS - Wide Area Augmentation System (FAA North America)
EGNOS – European Geo-stationary Navigation Overlay System
MSAS – Multifunctional transport Satellite-based Augmentations System (Japan)
SNAS – Satellite Navigation Augmentation System (China)
GRAS – Ground-based Regional Augmentation System (Australia – VHF)
For the RTG network, another set of reference/monitor sites are distributed across the entire world (sites in red).
For the WCT networks, a number of reference/monitor sites are distributed across the continental U.S., Europe, South America and Australia. (sites in green)
Each reference site sends dual frequency code and phase observables for all GPS satellites in view as well as system integrity information to two redundant network processing hubs (NPH) via terrestrial communication links (sites in blue) in North America (Redondo Beach, Ca & Moline, IL).

3. C-Nav Control Display Unit (CnC D.U.)
C-Nav[RM] GPS System
C-Nav GPS Receiver
C-Nav Control Display Unit (CnC D.U.)
The C-Nav system provides the user with industry standard NMEA sentence information. These are:-
GGA - Global Positioning System Fix Data
GLL - GPS Latitude and Longitude Data
GSA - GPS Mode, Satellites used for navigation, and DOP Data
GST - GPS Satellites Position Error Statistics (RAIM compliance)
RMC - GPS Recommended Minimum Specific Data
VTG - GPS Velocity, Track made good and Ground speed Data
ZDA - GPS UTC Date & Time Data
In addition, the C-Nav system provides additional NMEA sentence information in the form of ‘proprietary’ messages, as follows:-
NAVQ - StarFire Navigation Quality
NETQ - StarFire Network Quality ( to be implemented )
RXQ - StarFire Correction Signal Quality
SATS - GPS Dual Frequency (L1/L2) Satellites in view (similar to GSV message that only provide L1 frequency signal strength information).
Interconnect Cable

4. C-Nav[RM] is? A Worldwide ‘global’ GPS solution (RTG)
Provides deci-meter accuracy and stability
Simple ‘plug-n-play’ installation and use
Integrated ‘mast-head’ package minimizes equipment hardware requirements
Subscription Service activation and deactivation for long or short term usage
‘Regional’ backup solutions (WCT & SBAS)

5. Global Corrected GPS via StarFire Network
North & Central America (RTG, WCT, SBAS)
Western Europe / Mediterranean Sea (RTG, WCT, SBAS)
Far East Region (RTG, SBAS**)
Australia (RTG, WCT)
South America (RTG)
Eastern Europe / Mediterranean & Black Sea (RTG, SBAS)
African Continent (RTG)
Middle East, & Asian Continent (RTG)
Atlantic, Indian and Pacific Oceans (RTG)
** Waiting on MSAS
RTG corrections are available ‘globally’ within the Inmarsat communication satellite signal footprint (72deg N to 72deg South)
WCT corrections are available in North America, South America, Northern Europe and Australia.
SBAS corrections are available in North America (WAAS – mid 2003) and North West Europe (EGNOS – mid 2004)
MSAS corrections will be available for Japan / Far East when operational

6. America’s RTG Performance
Cumulative RTG Horizontal Solution performance analysis for January 2004 for the Americas region
The 95% confidence horizontal accuracy is 25 centimeters
The 1-sigma horizontal value is <10cms

7. Europe-Africa RTG Performance
Cumulative RTG Horizontal Solution performance analysis for January 2004 for the Europe Africa region
The 95% confidence horizontal accuracy is 22 centimeters
The 1-sigma horizontal value is <10cms

8. Asia-Australia RTG Performance
Cumulative RTG Horizontal Solution performance analysis for January 2004 for the Asia-Australia region
The 95% confidence horizontal accuracy is ~25 centimeters
The 1-sigma horizontal value is ~10cms

9. GcGPS Architecture
Global network of dual frequency GPS reference receivers which transmit their RAW observables to processing / distribution hubs (NPH)
Wide area communications used to broadcast corrections to users (StarFire)
Dual frequency GPS navigation receivers combined with wide area communication receiver
Measure / model key error sources (SV clock, orbit, local observed ionosphere, local troposphere)

10. Dual Frequency GcGPS Performance and Limitations
Decimeter level accuracy over very large areas (regional, continental, global)
Initialization time: 15 minutes to one hour (final accuracy)
Very low position drift rate in steady state
Limitations
Requires communication link to receive WADGPS corrections (sat. comm., other)
Potentially lengthy initialization time

11. Recent Improvements L1 phase navigation ‘smart’ position updates
Upstream (50Hz) measurement processing restructure
L1 phase nav. residual editing and cycle slip detection restructure
RTG backing RTK

12. Onshore GPS Stress Testing

13. A - Shading Areas - B

14. RTG w/o L1Pnav

15. RTG with L1Pnav

16. Overlay

17. Offshore Stress Testing

18. Vessel Setup

19. C-Nav Testing

20. C-Nav Testing

21. C-Nav Testing

22. C-Nav[2050] System
Work is underway to provide the next generation (or level) of C-Nav GPS product that will allow high-accuracy Real-Time Kinematic (RTK) capability for users and customers whilst still providing StarFire PVT solutions.
The latest development provides for RTK precision when operated in the ‘local area’ of an RTK base reference station but can automatically revert to ‘global’ RTG corrections (or regional WCT corrections) when outside of any RTK coverage.
Note: S.B.A.S. capability is also retained.

23. RTK and GcGPS Synergies
Q: If both RTK and dual frequency Starfire Wide Area DGPS (GcGPS) navigation solutions are available in the same system hardware/firmware, can they be combined to provide better performance?
A: Yes

24. Convential RTK Systems Typical Architecture
RTK base station: stationary, dual frequency GPS receiver generates local corrections
Terrestrial communications link used to transmit base station corrections to the RTK rover
RTK rover (navigator): dual frequency GPS receiver receives base station corrections and resolves carrier phase, integer ambiguities for satellites in view.

25. Convential RTK Systems Performance and Limitations
Centimeter level accuracy (1cm + 1ppm)
Effectively zero position drift rate
Initialization time: a few seconds to a few minutes
Limitations
Requires local base station and communication link to receive RTK correction data.
Operational area limited by range to base station
Range of communication link
Range limit for ambiguity resolution

26. Exploiting RTK and WADGPS Synergies
Initializing the WADGPS solution with RTK
Coasting’ through RTK outages using Carrier Phase RTG measurements
Re-initializing RTK using the WADGPS solution

27. The Problem

30. Questions? Refer to: http://www.cctechnol.com/cnav
for additional material and information
The C&C Technologies C-Nav WEB Site has additional information and material (Manuals, Papers, Related Links etc..).