1. GPS Modernization & WAAS
for the 10th Korean
GNSS Workshop
Nov. 21 & 22, 2003
by Per Enge
with thanks to the FAA
& my colleagues at Stanford University
copyright Per Enge, 2003

2. GPS Modernization New signals for frequency diversity
Integrity machines (WAAS & LAAS)
RFI hardening
other radio measurements (Loran-C, television signals, basic backup network)
receiver hardening (adaptive antennas, inertial measurements
assisted GPS
Ground control segment
a few new stations
a lot of new software
copyright Per Enge, 2003

3. GPS Ranging
copyright Per Enge, 2003

4. Scatter Plots (cartoons actually) for Stand Alone GPS & DGPS
1 m
1 m
5 m
5 m
copyright Per Enge, 2003

5. Scatter Plots for DGPS at Long Range & Differential Carrier Phase
1 m
1 m
5 m
5 m
copyright Per Enge, 2003

6. GPS Signals: Present and Future
Today’s satellites
New satellites launched
beginning in 2004
New satellites launched
near the end of the decade
copyright Per Enge, 2003

7. GPS Signal Components: Navigation Data, PRN Code & RF Carrier
6000 km
300 m
19 cm
copyright Per Enge, 2003

8. Auto-Correlation Properties
Time shift
between
replica code
and received
code
copyright Per Enge, 2003

9. Faster Codes Give Better Performance in Noise and Multipath
Correlation peak for
C/A code or RC code (1 Mcps)
-300 m
300 m
Correlation peak
for L5 code (10 Mcps)
-30 m
30 m
copyright Per Enge, 2003

10. Longer Codes Reduce Auto- & Cross-Correlation “Sidelobes”
100%
C/A code sidelobes:
6.4% of main peak
RC & L5 code sidelobes:
2.1% of main peak
copyright Per Enge, 2003

11. Ionospheric Measurement
copyright Per Enge, 2003

12. Wide Area Augmentation System Operational on July 10, 2003!
GPS constellation
Geostationary broadcast of
1.) Continental corrections
2.) Data for error bounds
3.) Ranging signal
Uplink
station
Central processor
Reference receivers
copyright Per Enge, 2003

13. Dual Frequency Ionospheric Estimation Vertical Iono
Dual Frequency Ionospheric Estimation Vertical Iono. on a Nominal Day (Juan Blanch)
copyright Per Enge, 2003

14. Dual Frequency Ionospheric Estimation Storm Day (July 16th 2000) (Juan Blanch)
copyright Per Enge, 2003

15. L1-only Single-Frequency Avionics (Dr. Shau Shiun Jan)
copyright Per Enge, 2003

16. L1-L5 Dual-frequency Avionics (Dr. Shau Shiun Jan)
copyright Per Enge, 2003

17. Radio Frequency Interference (RFI)
GPS constellation
RFI is most worrisome
& probably most likely
during approach
Airport Property
copyright Per Enge, 2003

18. Nominal Ionospheric Bound
Coasting on L5 if L1 is Lost to Interference (requires a new flag from the message)
L5-only WAAS
Coast to L5 With
Nominal Ionospheric Bound
<5
<10
<12
<15
<20
<30
<40
<50
>50
99.9% VPL (m)
copyright Per Enge, 2003

19. Summary GPS modernization includes: new signals integrity machines
RFI hardening
new ground control capability
All three pieces will work together to provide some truly amazing capabilities.
Three frequencies together will enable centimeter accuracies.
copyright Per Enge, 2003

20. Wide-Laning
300 m
19 cm
86 cm wavelength
copyright Per Enge, 2003

21. Beat Frequencies
copyright Per Enge, 2003