Satellite-Based Augmentation System (SBAS) Terminology
Purpose
This note defines recurring SBAS terms used across the knowledge base. It is now a controlled terminology page, not the main beginner explanation. New readers should start with What is SBAS and then continue to SBAS Architecture.
Definitions here are concise and intentionally conservative. Exact operational thresholds, message definitions, approval criteria, and service-performance commitments must be traced to the relevant source notes and official documents before being used as authoritative requirements.
Core terms
| Term | Working definition | Related notes |
|---|---|---|
| SBAS | Wide-area GNSS augmentation service that broadcasts correction and integrity information to users | What is SBAS, SBAS Architecture |
| GNSS | Satellite navigation constellations and signals used as the base positioning source | SBAS Architecture |
| Reference station | Surveyed ground receiver used to monitor GNSS signal behavior for augmentation processing | SBAS Architecture |
| Master or processing station | Facility/function that estimates corrections, integrity parameters, and broadcast messages | SBAS Architecture |
| Uplink station | Ground element that sends SBAS messages to the broadcast satellite or payload | SBAS Architecture Flow |
| SBAS broadcast | Signal carrying augmentation messages to user receivers | SBAS Architecture Flow |
| SBAS-capable receiver | User equipment able to receive, decode, and apply SBAS information according to its approval basis | SBAS Ground Segment and Airborne Receiver Responsibilities |
| SBAS message flow | Functional path from monitored observations through augmentation messages to receiver processing | SBAS Signal and Message Flow |
| Correction | Information used to reduce modeled navigation errors where applicable | SBAS Corrections and Integrity Separation |
| Integrity | Ability to support timely warning when navigation information should not be relied upon for the intended operation | SBAS Integrity |
| Protection level | Receiver-computed or service-supported bound used to judge whether navigation error remains acceptable for an operation | Protection Levels |
| Alert limit | Operation-specific bound that protection levels must satisfy for the operation to continue | Alert Limits |
| Availability | Probability or proportion of time that service requirements are met in the relevant context | SBAS-Systems-by-Region-MOC |
| Continuity | Probability that service remains available for the duration of a defined operation | SBAS in Civil Aviation MOC |
| LPV | Localizer Performance with Vertical guidance; an SBAS-enabled approach concept where approved | LPV-Approach-Procedure |
| APV | Approach with vertical guidance; operational family relevant to GNSS/SBAS implementation | SBAS in Civil Aviation MOC |
| GBAS | Ground-Based Augmentation System; local-area augmentation, usually airport-centered | GBAS-Approach-Procedure, SBAS-vs-Other-Augmentation-Methods |
| ABAS | Aircraft-Based Augmentation System; receiver/aircraft-side monitoring rather than a regional broadcast service | SBAS-vs-Other-Augmentation-Methods, ASEAN ABAS Concept |
Terms requiring careful source handling
The following terms are frequently misused or over-generalized:
- Accuracy: must be tied to a metric, confidence level, service mode, and source.
- Integrity: should not be reduced to “high accuracy”; it is about bounding and alerting.
- Availability: may refer to signal availability, service availability, procedure availability, or operational availability; these are not interchangeable.
- Operational: can mean a live technical service, a certified aviation service, a published procedure, or an approved aircraft operation. State which meaning is intended.
- Coverage: a coverage footprint does not automatically imply approved procedures or service-level compliance at every airport.
- Readiness: in regional implementation analysis, readiness includes institutional, regulatory, AIS/AIM, procedure-design, aircraft-equipage, and safety-oversight dimensions.
Source posture
Terminology in this page is aligned with the site’s current synthesis and source scaffolds. High-priority source anchors include:
- SBAS Standards Source Matrix
- SBAS Core Claim Routing
- Source - RTCA DO-229
- Source - ICAO Annex 10 Volume I GNSS SBAS
- Source - ICAO Doc 9849
- Source - EASA ETSO-C145e and ETSO-C146e
- SBAS Operational Validation Dashboard
See also
- What is SBAS
- SBAS Architecture
- SBAS Architecture Flow
- SBAS Signal and Message Flow
- SBAS Corrections and Integrity Separation
- SBAS Ground Segment and Airborne Receiver Responsibilities
- SBAS Core Claim Routing
- SBAS Integrity
- Protection Levels
- Alert Limits
- Safety-Terminology
- Communication-Terminology
- SBAS-vs-Other-Augmentation-Methods
- SBAS-Standards-Regulation