Transcript ESEP - Centrum Badań Kosmicznych

Wide Area Augmentation System
(WAAS)
E. Douglas Aguilar
CAPT, USAF
Development

Joint project between
– Federal Aviation Administration (FAA)
– US Department of Transportation (DOT)

Goal
– Provide horizontal and vertical navigation for
precision approaches for everyone everywhere
Continental US
Error Sources
One Sigma Error (m)
GPS Error Sources
Normal C/A Code
Dual (P/Y)
Ionosphere
4.00
1.20
Satellite clock
2.10
2.10
Ephemeris data
2.10
2.10
Multipath
1.40
1.40
Troposphere
0.70
0.70
Receiver measurement
0.50
0.50
UERE (rms)
5.25
3.60
UERE Filtered (rms)
5.10
3.30
WAAS
EGNOS
Vertical DOP=2.5
12.75
8.25
3.00
4.00
Horizontal DOP=2.0
10.20
6.60
3.20
2.00
Timeline

Phase I (1998-2002)
– 25 reference stations, 2 master stations and 2
satellites deployed
– Supports category I precision approach, limited
coverage area
Timeline

Phase II (2003-2007)
– Full WAAS expected with additional reference and
master stations
– Airports begin upgrading landing systems
– 2nd and 3rd civil frequencies added to improve
accuracy
Timeline

Phase III (2008-2015)
– Full constellation of GPS satellites available for
WAAS
– Phase out all airport navigational aids and fully
integrate WAAS for commercial aircraft
WAAS
Space Based Augmentation Systems

WAAS Elements as of Nov 2006
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Only in US
29 Wide-area reference stations (WRS)
3 Wide-area monitoring stations (WMS)
3 Ground earth stations (GES)
2 to 4 geosynchronous satellites
(EGNOS)
(23 countries)
(34 RIMS)
(4MCC)
(6 NLES)
(3)
WAAS Components
WAAS Functions
Function 5 - Integrity

INPUTS
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
GPS satellite navigation data
GEO satellite navigation data
antenna phase center locations
satellite long term error corrections
IGP locations
IGP vertical ionosopheric delay estimate
IPG GIVE data
Satellite User differential range error (UDRE) data
message type 10 degradation parameters
fast correction degradation factor
OUTPUTS
– data to generate “Don’t Use” messages
– data to generate “Not Monitored” messages
– list of satellites that should be in view but whose signals are not being received
Function 5 shall generate data for a “Don’t Use” message for any satellite
whose pseudorange errors are not correctable within the limits of the WASS
message structure
Architecture
Commercial Aircraft
Benefits
Nav/Landing Equipment
FAA Announcement

FAA Announces Major
Milestone for Wide Area
Augmentation System
(WAAS)– FAA Administrator Marion
C. Blakey. “Less reliance
on a ground-based
infrastructure will result in
improved safety, including
enhanced approach and
landing operations in
marginal weather.”
LNAV/VNAV 350’
LPV 250’
ILS 200’
3o
March 24, 2006- WAAS use will be
extended to 200 feet above an
airport’s surface
http://www.faa.gov/news/press_release
s/news_story.cfm
Coverage
WAAS Satellites

Original two Inmarsat III
– PRN#134 Pacific Ocean Region
– PRN #122 Atlantic Ocean Region

Two additional
– PRN #135 Galaxy XV (as of Nov 9th 2006)
– PRN #138 ANIK F1R (under testing)
Issues
 Accuracy
– Geo satellites are low on horizon accuracy
may degrade in Canada-Alaska
– Correction will decrease in accuracy with
distance from reference station
 Costly
-
– Update airports and receivers
– Installation of ground stations and satellites
Future Improvements

Nine new Wide-area Reference stations
– Summer 2007
 3 Mexico
 2 Canada
– Fall 2007
 2 Mexico
 2 Canada
Sources

Federal Aviation Agency website (http://gps.faa.gov)
– Papers
 “Wide-Area Augmentation System Performance Analysis Report” April 2002
 “DOD and FAA Specification for the Wide Area Augmentation System” August
2001
– Presentations
 “WAAS” Dan Hanlon, Program Manager, April 2003
 “Satellite Navigation Program” August 2000

Free Flight Systems
– http://www.freeflightsystems.com/waas.htm
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WIKIPEDIA
– http://en.wikipedia.org/wiki/WAAS#Operation

Research Papers
– “Performance Analysis of GPS Positioning Using WAAS and EGNOS” Dr.
Abousalem, Mr. Tubalin; Ashtech Precision Products, May 2000
Questions?