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SBAS Fundamentals: Difference between revisions
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A [Satellite-based Augmentation System (SBAS) is a civil aviation safety-critical system that supports wide-area or regional augmentation – even continental scale - through the use of geostationary (GEO) satellites which broadcast the augmentation information<ref name="GNSS Aug"/><ref name="Kaplan"/>. A SBAS augments primary GNSS constellation(s) by providing GEO ranging, [[Integrity|integrity]] and correction information. While the main goal of SBAS is to provide [[Integrity|integrity]] assurance, it also increases the [[Accuracy|accuracy]] with position errors below 1 metre (1 sigma). | |||
The ground infrastructure includes the accurately-surveyed sensor stations which receive the data from the primary GNSS satellites and a Central Processing Facility (CPF) which computes [[Integrity|integrity]], corrections and GEO ranging data forming the SBAS signal-in-space (SIS). The SBAS GEO satellites relay the SIS to the SBAS users which determine their position and time information. For this, they use measurements and satellite positions both from the primary GNSS constellation(s) and the SBAS GEO satellites and apply the SBAS correction data and its [[Integrity|integrity]]. | |||
The augmentation information provided by SBAS covers corrections and [[Integrity|integrity]] for satellite position errors, satellite clock – time - errors and errors induced by the estimation of the delay of the signal while crossing the [[Ionospheric Delay|ionosphere]]. For the errors induced by the estimation of the delay caused by the [[Tropospheric Delay|troposphere]] and its integrity, the user applies a [[Tropospheric Delay|tropospheric delay]] model. | |||
==SBAS Performances== | |||
The SBAS performances are defined with respect to the level of service that the system is designed to. The main source for SBAS performances comes from civil aviation navigation safety requirements and they are different for each civil aviation operation (see Table ICAO GNSS performances requirements <ref name=”ICAO SARPS”>ICAO Standards and Recommended Practices, Annex 10, Volume 1 Radio Navigation Aids, July 2006</ref>). | |||
{| class="wikitable" | |||
|- | |||
!|Typical Operation||Horizontal Accuracy (95%)||Vertical Accuracy (95%)||Integrity||Time-To-Alert (TTA)||Horizontal Alert Limit (HAL)||Vertical Alert Limit (HAL)||Continuity||Availability | |||
|- | |||
|Initial Intermediate Nonprecision approaches & Departure||220 m (720 ft)||N/A||1 –1x10-7/h||10 s||556 m (0.3 NM)||N/A||1 – 1x10-4/h to 1 – 1x10-8/h||0.99 to 0.99999 | |||
|- | |||
|Approach operations with vertical guidance (APV-I)||16.0 m (52 ft) ||20 m (66 ft) ||1 – 2x10-7 (per approach)||10 s ||40 m (130 ft) ||50 m (164 ft) ||1 – 8x10-6/15s ||0.99 to 0.99999 | |||
|} | |||
==Notes== | ==Notes== | ||
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[[Category:Fundamentals]] | [[Category:Fundamentals]] | ||
[[Category:SBAS]] | |||
Revision as of 13:25, 1 April 2011
| Fundamentals | |
|---|---|
| Title | SBAS Fundamentals |
| Author(s) | GMV |
| Level | Basic |
| Year of Publication | 2011 |
A [Satellite-based Augmentation System (SBAS) is a civil aviation safety-critical system that supports wide-area or regional augmentation – even continental scale - through the use of geostationary (GEO) satellites which broadcast the augmentation information[1][2]. A SBAS augments primary GNSS constellation(s) by providing GEO ranging, integrity and correction information. While the main goal of SBAS is to provide integrity assurance, it also increases the accuracy with position errors below 1 metre (1 sigma).
The ground infrastructure includes the accurately-surveyed sensor stations which receive the data from the primary GNSS satellites and a Central Processing Facility (CPF) which computes integrity, corrections and GEO ranging data forming the SBAS signal-in-space (SIS). The SBAS GEO satellites relay the SIS to the SBAS users which determine their position and time information. For this, they use measurements and satellite positions both from the primary GNSS constellation(s) and the SBAS GEO satellites and apply the SBAS correction data and its integrity.
The augmentation information provided by SBAS covers corrections and integrity for satellite position errors, satellite clock – time - errors and errors induced by the estimation of the delay of the signal while crossing the ionosphere. For the errors induced by the estimation of the delay caused by the troposphere and its integrity, the user applies a tropospheric delay model.
SBAS Performances
The SBAS performances are defined with respect to the level of service that the system is designed to. The main source for SBAS performances comes from civil aviation navigation safety requirements and they are different for each civil aviation operation (see Table ICAO GNSS performances requirements [3]).
| Typical Operation | Horizontal Accuracy (95%) | Vertical Accuracy (95%) | Integrity | Time-To-Alert (TTA) | Horizontal Alert Limit (HAL) | Vertical Alert Limit (HAL) | Continuity | Availability |
|---|---|---|---|---|---|---|---|---|
| Initial Intermediate Nonprecision approaches & Departure | 220 m (720 ft) | N/A | 1 –1x10-7/h | 10 s | 556 m (0.3 NM) | N/A | 1 – 1x10-4/h to 1 – 1x10-8/h | 0.99 to 0.99999 |
| Approach operations with vertical guidance (APV-I) | 16.0 m (52 ft) | 20 m (66 ft) | 1 – 2x10-7 (per approach) | 10 s | 40 m (130 ft) | 50 m (164 ft) | 1 – 8x10-6/15s | 0.99 to 0.99999 |
Notes