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|Title={{PAGENAME}}
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|Level=Basic
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The Wide Area Augmentation System ([[WAAS General Introduction|WAAS]]) is the United States [[SBAS General Introduction|Satellite Based Augmentation System]]. The programme, started in 1992, is being carried out by the [http://www.faa.gov/ Federal Aviation Agency (FAA)]<ref name="FAA_NAV_HISTORY">[http://www.faa.gov Navigation Services - History - Satellite Navigation,] [http://www.faa.gov/ FAA.]</ref> and is specially developed for the civil aviation community.<ref name="FAA_WAAS">[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/waas/ Navigation Services - Wide Area Augmentation System (WAAS)], [http://www.faa.gov/ FAA.]</ref> The system, which was declared operational on July 10, 2003on July 10, 2003,<ref name="STANFORD_WAAS">[https://gps.stanford.edu/research/currentcontinuing-research/waas-sbas Wide Area Differential GPS (WADGPS), Stanford University]</ref> currently supports thousands of aircraft instrument approaches in more than one thousand airports in USA and Canada.<ref name="APPROACHES">[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/approaches/index.cfm GNSS - GPS/WAAS Approaches,] [http://www.faa.gov/ Federal Aviation Agency (FAA).]</ref> WAAS service area includes CONUS, Alaska, Canada and Mexico.<ref name="WAASExpanded">[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/waas/news/ WAAS Service Expanded into Canada and Mexico, September 28, 2007,] [http://www.faa.gov/ Federal Aviation Agency (FAA).]</ref>  The WAAS programme is continuously in evolution; three development phases have been already covered, and there are on-going plans to improve the capability of the system in parallel with the evolution of the SBAS standards towards a dual-frequency augmentation service.<ref name="EXTENSION">[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/library/satnav/media/SatNav_March08.pdf SatNav News, Vol. 33, March 2008,] [http://www.faa.gov/ Federal Aviation Agency (FAA).]</ref>, <ref name="STANFORD_WAAS"/>
==WAAS Performance==
Satellite Based Augmentation Systems ([[SBAS General Introduction|SBAS]]) performances are usually described in terms of [[Integrity|integrity]], [[Accuracy|accuracy]], [[Availability|availability]], and [[Continuity|continuity]].
According to the WAAS performance standard,<ref name=WAAS_PSTD>[http://www.gps.gov/technical/ps/2008-WAAS-performance-standard.pdf Global Positioning System Wide Area Augmentation System (WAAS) Performance Standard,] Department of Transportation and Federal Aviation Administration, USA, 1st Edition, 31 October 2008.</ref> WAAS service area is divided in five coverage zones:
*Zone 1: CONUS.
*Zone 2: Alaska.
*Zone 3: Hawaii.
*Zone 4: Puerto Rico and some other Caribbean islands.
*Zone 5: US territory excluding zones 1 to 4.
The volume covered includes a region up to 100.000 feet above the surface. For zones 1 to 3, the area extends up to 30 nm outside the land.
<gallery perrow="5">
Image:WAAS_zone_1.jpg | Zone 1
Image:WAAS_zone_2.jpg | Zone 2
Image:WAAS_zone_3.jpg | Zone 3
Image:WAAS_zone_4.jpg | Zone 4
Image:WAAS_zone_5.jpg | Zone 5
</gallery>


The Wide Area Augmentation System (WAAS) is an [[GNSS Augmentation|GPS Augmentation]] system developed by the [http://www.faa.gov Federal Aviation Administration (FAA)], with the goal of improving its accuracy, integrity, and availability. Essentially, WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including precision approaches to any airport within its coverage area.


==WAAS Performances==
WAAS specification distinguishes the following flight phases:<ref name=WAAS_PSTD/>
*En route
*Terminal
*LNAV (Lateral Navigation)
*LNAV/VNAV (Lateral Navigation/Vertical Navigation)
*LPV (Localizer Performance with Vertical guidance)
*LPV 200 (LPV 200 foot minimum)


Performances are usually described in terms of accuracy, integrity, availability and continuity. The WAAS specification Performance Requirements<ref> FAA.[http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/library/documents/media/waas/2892bC2a.pdf ''Specification for the Wide Area Augmentation System(WAAS)'']. FAA-E- 2892b. August 13, 2001.</ref> are different depending on the phase of the flight: en route through 1)  Non-precision approach (NPA) and 2) Precision Approach.
The requirements considering the different flight phases and coverage zones are summarised in the next table:<ref name=WAAS_PSTD/>


# WAAS Performance Requirements for Non-Precision Approach are summarized in the following table:
{| class="wikitable" align="center"
{| class="wikitable" align="center"
! Performance Requirement
|+align="bottom" |''WAAS Navigation Performance Requirements''
! Total System
!
! Navigation System
! En Route
! WAAS Signal-in-Space
! Terminal
! Airborne
! LNAV
|-
! LNAV/VNAV
! Availability
! LPV
| 0.999
! LPV 200
| 0.999
|- align="center"
| 0.999
! TTA
| Not Specified (N/S)
| 15 s
|-
| 15 s
| '''Accuracy''' <br /> 95% Horizontal Position <br /> 99.999% Horizontal Position <br /> 95% Vertical Position <br /> 95% Pseudorange
| 10 s
| <br /> N/S <br /> N/S <br /> N/A <br /> N/A
| 10 s
|-
| 6.2 s
| '''Pacific Ocean Region (POR)''' <br />''Ceased WAAS transmissions''
| 6.2 s
|NMEA #47 / PRN #134
|- align="center"
|178°E
! HAL
|-
| 2 nm
| '''Atlantic Ocean Region-West''' <br />''Ceased WAAS transmissions''
| 1 nm
|NMEA #35 / PRN #122
| 556 m
|142°W
| 556 m
| 40 m
| 40 m
|- align="center"
! VAL
| N/A
| N/A
| N/A
| 50 m
| 50 m
| 35 m
|- align="center"
! Probability of HMI
| 10<sup>-7</sup> per hour
| 10<sup>-7</sup> per hour
| 10<sup>-7</sup> per hour
| 2 x 10<sup>-7</sup> per approach
| 2 x 10<sup>-7</sup> per approach (150 seconds)
| 2 x 10<sup>-7</sup> per approach (150 seconds)
|- align="center"
! Zone 1 Continuity
| 1 - 10<sup>-5</sup> per hour
| 1 - 10<sup>-5</sup> per hour
| 1 - 10<sup>-5</sup> per hour
| 1 - 5.5 x 10<sup>-5</sup>/15 seconds
| 1 - 8 x 10<sup>-6</sup>/15 seconds
| 1 - 8 x 10<sup>-6</sup>/15 seconds
|- align="center"
! Horizontal Accuracy (95%)
| 0.4 nm
| 0.4 nm
| 220 m
| 220 m
| 16 m
| 16 m
|- align="center"
! Vertical Accuracy (95%)
| N/A
| N/A
| N/A
| 20 m
| 20 m
| 4 m
|- align="center"
! Availability (Zone 1 Coverage)
| 0.99999 (100%)
| 0.99999 (100%)
| 0.99999 (100%)
| 0.99 (100%)
| 0.99 (80-100%)
| 0.99 (40-60%)
|- align="center"
! Availability (Zone 2 Coverage)
| 0.999 (100%)
| 0.999 (100%)
| 0.999 (100%)
| 0.95 (75%)
| 0.95 (75%)
| N/A
|- align="center"
! Availability (Zone 3 Coverage)
| 0.999 (100%)
| 0.999 (100%)
| 0.999 (100%)
| N/A
| N/A
| N/A
|- align="center"
! Availability (Zone 4 Coverage)
| 0.999 (100%)
| 0.999 (100%)
| 0.999 (100%)
| N/A
| N/A
| N/A
|- align="center"
! Availability (Zone 5 Coverage)
| 0.99999 (100%)
| 0.999 (100%)
| 0.999 (100%)
| N/A
| N/A
| N/A
|}
|}
# WAAS Performance Requirements for Precision Approach are summarized in the following table:
 
In this table, the integrity requirements are given as the probability of HMI, namely Hazardously Misleading Information. In addition to integrity, accuracy, availability and continuity, the table shows the specification for Time To Alert (TTA) and for Horizontal and Vertical Alert Limits (HAL and VAL).
 
On July 10, 2003, the WAAS system was certified for safety-of-life aviation, covering 95% of the contiguous U.S. and part of Alaska <ref name="STANFORD_WAAS"/><ref>[http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System Wide Area Augmentation System]</ref>. At present, WAAS supports en-route, terminal and approach operations down to a full LPV-200 (CAT-I like Approach Capability) for the CONUS, Mexico and Canada.
 
The FAA publishes real time WAAS performance at the [http://www.nstb.tc.faa.gov Technical Center WAAS Test Bed web site].<ref name="WTB"/> Typical performances provided by WAAS System when considering operating in LPV (Horizontal Alarm Limit = 40 m , Vertical Alarm Limit =50 m) are shown in next figure:<ref name="WTB">[http://www.nstb.tc.faa.gov/24Hr_WaasLPV200.htm FAA Monitoring WAAS Performances in Real-Time]</ref>
 
[[File:WAAS_performance.png|center|thumb|400px|WAAS LPV Coverage<ref>[https://www.nstb.tc.faa.gov/24Hr_WaasLPV.htm WAAS LPV performance in Federal Aviation Administration website]</ref>]]


==Notes==
==Notes==
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==References==
==References==
<references/>
<references/>
[[Category:WAAS]]

Latest revision as of 09:10, 16 February 2021


WAASWAAS
Title WAAS Performances
Edited by GMV
Level Basic
Year of Publication 2011
Logo GMV.png

The Wide Area Augmentation System (WAAS) is the United States Satellite Based Augmentation System. The programme, started in 1992, is being carried out by the Federal Aviation Agency (FAA)[1] and is specially developed for the civil aviation community.[2] The system, which was declared operational on July 10, 2003on July 10, 2003,[3] currently supports thousands of aircraft instrument approaches in more than one thousand airports in USA and Canada.[4] WAAS service area includes CONUS, Alaska, Canada and Mexico.[5] The WAAS programme is continuously in evolution; three development phases have been already covered, and there are on-going plans to improve the capability of the system in parallel with the evolution of the SBAS standards towards a dual-frequency augmentation service.[6], [3]

WAAS Performance

Satellite Based Augmentation Systems (SBAS) performances are usually described in terms of integrity, accuracy, availability, and continuity. According to the WAAS performance standard,[7] WAAS service area is divided in five coverage zones:

  • Zone 1: CONUS.
  • Zone 2: Alaska.
  • Zone 3: Hawaii.
  • Zone 4: Puerto Rico and some other Caribbean islands.
  • Zone 5: US territory excluding zones 1 to 4.

The volume covered includes a region up to 100.000 feet above the surface. For zones 1 to 3, the area extends up to 30 nm outside the land.

  • Zone 1

    Zone 1

  • Zone 2

    Zone 2

  • Zone 3

    Zone 3

  • Zone 4

    Zone 4

  • Zone 5

    Zone 5


WAAS specification distinguishes the following flight phases:[7]

  • En route
  • Terminal
  • LNAV (Lateral Navigation)
  • LNAV/VNAV (Lateral Navigation/Vertical Navigation)
  • LPV (Localizer Performance with Vertical guidance)
  • LPV 200 (LPV 200 foot minimum)

The requirements considering the different flight phases and coverage zones are summarised in the next table:[7]

WAAS Navigation Performance Requirements
En Route Terminal LNAV LNAV/VNAV LPV LPV 200
TTA 15 s 15 s 10 s 10 s 6.2 s 6.2 s
HAL 2 nm 1 nm 556 m 556 m 40 m 40 m
VAL N/A N/A N/A 50 m 50 m 35 m
Probability of HMI 10-7 per hour 10-7 per hour 10-7 per hour 2 x 10-7 per approach 2 x 10-7 per approach (150 seconds) 2 x 10-7 per approach (150 seconds)
Zone 1 Continuity 1 - 10-5 per hour 1 - 10-5 per hour 1 - 10-5 per hour 1 - 5.5 x 10-5/15 seconds 1 - 8 x 10-6/15 seconds 1 - 8 x 10-6/15 seconds
Horizontal Accuracy (95%) 0.4 nm 0.4 nm 220 m 220 m 16 m 16 m
Vertical Accuracy (95%) N/A N/A N/A 20 m 20 m 4 m
Availability (Zone 1 Coverage) 0.99999 (100%) 0.99999 (100%) 0.99999 (100%) 0.99 (100%) 0.99 (80-100%) 0.99 (40-60%)
Availability (Zone 2 Coverage) 0.999 (100%) 0.999 (100%) 0.999 (100%) 0.95 (75%) 0.95 (75%) N/A
Availability (Zone 3 Coverage) 0.999 (100%) 0.999 (100%) 0.999 (100%) N/A N/A N/A
Availability (Zone 4 Coverage) 0.999 (100%) 0.999 (100%) 0.999 (100%) N/A N/A N/A
Availability (Zone 5 Coverage) 0.99999 (100%) 0.999 (100%) 0.999 (100%) N/A N/A N/A

In this table, the integrity requirements are given as the probability of HMI, namely Hazardously Misleading Information. In addition to integrity, accuracy, availability and continuity, the table shows the specification for Time To Alert (TTA) and for Horizontal and Vertical Alert Limits (HAL and VAL).

On July 10, 2003, the WAAS system was certified for safety-of-life aviation, covering 95% of the contiguous U.S. and part of Alaska [3][8]. At present, WAAS supports en-route, terminal and approach operations down to a full LPV-200 (CAT-I like Approach Capability) for the CONUS, Mexico and Canada.

The FAA publishes real time WAAS performance at the Technical Center WAAS Test Bed web site.[9] Typical performances provided by WAAS System when considering operating in LPV (Horizontal Alarm Limit = 40 m , Vertical Alarm Limit =50 m) are shown in next figure:[9]

WAAS LPV Coverage[10]

Notes

References

  1. ^ Navigation Services - History - Satellite Navigation, FAA.
  2. ^ Navigation Services - Wide Area Augmentation System (WAAS), FAA.
  3. ^ a b c Wide Area Differential GPS (WADGPS), Stanford University
  4. ^ GNSS - GPS/WAAS Approaches, Federal Aviation Agency (FAA).
  5. ^ WAAS Service Expanded into Canada and Mexico, September 28, 2007, Federal Aviation Agency (FAA).
  6. ^ SatNav News, Vol. 33, March 2008, Federal Aviation Agency (FAA).
  7. ^ a b c Global Positioning System Wide Area Augmentation System (WAAS) Performance Standard, Department of Transportation and Federal Aviation Administration, USA, 1st Edition, 31 October 2008.
  8. ^ Wide Area Augmentation System
  9. ^ a b FAA Monitoring WAAS Performances in Real-Time
  10. ^ WAAS LPV performance in Federal Aviation Administration website
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