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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/about/office_org/headquarters_offices/ato/service_units/techops/navservices/history/satnav/index.cfm 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 in late 2003,<ref name="STANFORD_WAAS">[http://waas.stanford.edu/research/waas.htm 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; two development phases have been already covered, a third is in progress, and there are 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>
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/about/office_org/headquarters_offices/ato/service_units/techops/navservices/history/satnav/index.cfm 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 in late 2003,<ref name="STANFORD_WAAS">[http://waas.stanford.edu/research/waas.htm 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; two development phases have been already covered, a third is in progress, and there are 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>


 
==WAAS Performance==
==WAAS Performances==
 
Satellite Based Augmentation Systems ([[SBAS General Introduction|SBAS]]) performances are usually described in terms of [[Integrity|integrity]], [[Accuracy|accuracy]], [[Availability|availability]], and [[Continuity|continuity]]. The WAAS specification performance requirements<ref name="WAAS SPEC">[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, [http://www.faa.org FAA].</ref> depend on the phase of the flight: 1) en route through non-precision approach (NPA) and 2) precision approach.
 
According to its specification document, WAAS performance requirements are the following:<ref name="WAAS SPEC"/>
:1. WAAS Performance Requirements for '''''En Route through 'Non-Precision Approach''''''
{| class="wikitable" align="center"
|+align="bottom" |''Performances Requirements for En Route through Non-Precision Approach''
! Performance Requirement
! Total System
! Navigation System
! WAAS Signal-in-Space
! Airborne
|- align="center"
! Availability
| 0.99999
| 0.99999
| 0.99999
| N/S
|- align="center"
| '''Accuracy''' <br /> 95% Horizontal Position <br /> 99.999% Horizontal Position <br /> 95% Vertical Position <br /> 95% Pseudorange
|  <br /> N/S <br /> N/S <br /> N/A <br /> N/A 
|  <br /> 100 m <br /> 500 m <br /> N/A <br /> N/S 
|  <br /> N/S <br /> N/S <br /> N/A <br /> N/S
|  <br /> N/S <br /> N/S <br /> N/A <br /> 1.2 m
|- align="center"
| '''Integrity''' <br /> Integrity Risk <br /> Time-to-Alarm
|  <br /> N/S <br /> 10 s 
|  <br /> N/S <br /> 10 s
|  <br /> 10<sup>-7</sup>/hour <br /> 8 s
|  <br /> N/S <br /> 2 s
|- align="center"
| '''Continuity''' <br /> Continuity of Navigation <br /> Continuity of Fault Detection (1)
|  <br /> 1 - 10<sup>-5</sup>/hour <br /> 1 - (2x10<sup>-5</sup>)/hour
|  <br /> 1 - 10<sup>-5</sup>/hour <br /> 1 - (2x10<sup>-5</sup>)/hour 
|  <br /> 1 - 10<sup>-8</sup>/hour <br /> 1 - 10<sup>-5</sup>/hour 
|  <br /> 1 - 10<sup>-5</sup>/hour <br /> 1 - 10<sup>-5</sup>/hour 
|}<br>
::(1) Excluding outages of less than 5 minutes.
 
 
:2. WAAS Performance Requirements for '''Precision Approach'''
{| class="wikitable" align="center"
|+align="bottom" |''Performances Requirements for Precision Approach''
! Performance Requirement
! Total System
! Navigation System
! GPS/WAAS Signal-in-Space
! Airborne
|- align="center"
! Availability
| N/S
| N/S
| 0.999
| N/S
|- align="center"
| '''Accuracy''' <br /> 95% Horizontal Position <br /> 95% Vertical Position <br /> 95% Pseudorange
|  <br /> 33.5 m <br /> 9.8 m <br /> N/A 
|  <br /> 7.6 m <br /> 7.6 m <br /> N/S 
|  <br /> N/S <br /> N/S <br /> N/S
|  <br /> N/S <br /> N/S  <br /> 1.2 m
|- align="center"
| '''Integrity''' <br /> Integrity Risk <br /> Time-to-Alarm
|  <br /> N/S <br /> N/S 
|  <br /> N/S <br /> N/S
|  <br /> 10<sup>-7</sup>/approach <br /> 5.2 s
|  <br /> N/S <br /> N/S
|- align="center"
| '''Continuity''' <br /> Continuity of Navigation <br /> Continuity of Fault Detection
|  1 - 10<sup>-4</sup>/approach <br /> N/S <br /> N/S
|  1 - 10<sup>-4</sup>/approach <br /> N/S <br /> N/S
|  1 - (5.5x10<sup>-5</sup>)/approach <br /> N/S <br /> N/S
|  1 - (4.5x10<sup>-5</sup>)/approach <br /> N/S <br /> N/S
|}
::''N/S'' stands for ''Not Specified''.
::''N/A'' stands for ''Not Applicable''.
 
On July 10, 2003, the WAAS system was certified for for safety-of-life aviation, covering 95% of the United States, and portions of Alaska <ref name="STANFORD_WAAS">[http://waas.stanford.edu/research/waas.htm Wide Area Differential GPS (WADGPS), Stanford University]</ref><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. 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>[http://www.nstb.tc.faa.gov/24Hr_WaasLPV200.htm FAA Monitoring WAAS Performances in Real-Time]</ref>
 
[[File:WAASCoverage LPV.png|center|thumb|400px|Typical WAAS LPV Coverage]]
 
 
==WAAS Signal-In-Space Performance Requirements==
Satellite Based Augmentation Systems ([[SBAS General Introduction|SBAS]]) performances are usually described in terms of [[Integrity|integrity]], [[Accuracy|accuracy]], [[Availability|availability]], and [[Continuity|continuity]].
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 peformance standard<ref name=WAAS_PSTD>[http://www.pnt.gov/public/docs/2008/waasps2008.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:
According to the WAAS performance standard<ref name=WAAS_PSTD>[http://www.pnt.gov/public/docs/2008/waasps2008.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 1: CONUS.
*Zone 2: Alaska.
*Zone 2: Alaska.
Line 101: Line 17:
*Zone 4: Puerto Rico and some other Caribbean islands.
*Zone 4: Puerto Rico and some other Caribbean islands.
*Zone 5: US territory excluding zones 1 to 4.
*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 4, the area extends up to 30 nm outside the land.
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>
 


WAAS specification distiguishes the following flight phases:
WAAS specification distinguishes the following flight phases:<ref name=WAAS_PSTD/>
*En route
*En route
*Terminal
*Terminal
Line 111: Line 36:
*LPV 200 (LPV 200 foot minimum)
*LPV 200 (LPV 200 foot minimum)


The requirements considering the different flight phases and the different coverage zones are summarised in the next table:<ref name=WAAS_PSTD/>
The requirements considering the different flight phases and coverage zones are summarised in the next table:<ref name=WAAS_PSTD/>


{| class="wikitable" align="center"
{| class="wikitable" align="center"
Line 221: Line 146:


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).
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 United States, and portions of Alaska <ref name="STANFORD_WAAS">[http://waas.stanford.edu/research/waas.htm Wide Area Differential GPS (WADGPS), Stanford University]</ref><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:WAASCoverage LPV.png|center|thumb|400px|Typical WAAS LPV Coverage]]




Revision as of 15:05, 22 November 2011


WAASWAAS
Title WAAS Performances
Author(s) 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 in late 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; two development phases have been already covered, a third is in progress, and there are plans to improve the capability of the system in parallel with the evolution of the SBAS standards towards a dual-frequency augmentation service.[6]

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 United States, and portions 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]

Typical WAAS LPV Coverage



Notes

References

  1. ^ Navigation Services - History - Satellite Navigation, FAA.
  2. ^ Navigation Services - Wide Area Augmentation System (WAAS), FAA.
  3. ^ a b 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
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