SBAS Ranging Sources and Time Reference
Purpose
This note explains where SBAS ranging-source and time-reference claims belong in the knowledge base.
It is a core mechanism routing note, not a message specification, timing-accuracy table, or receiver-approval statement.
Non-overlap rule
This note owns only the conceptual separation among:
- GNSS constellation ranging signals;
- SBAS broadcast support;
- any source-supported SBAS GEO ranging or ranging-like role;
- time-reference alignment as a standards/service concept;
- receiver use of these inputs.
It does not own:
- message contents — use SBAS Signal and Message Flow;
- correction categories — use SBAS Correction Timescale Taxonomy;
- integrity/useability bounds — use SBAS Integrity Data and User Bounds;
- receiver modes — use SBAS Receiver Modes and Annunciation;
- operational use — use SBAS Standards to Operations Evidence Ladder.
Conceptual layers
| Layer | Safe concept-level statement | Evidence family before detail |
|---|---|---|
| GNSS ranging source | The user receiver derives measurements from GNSS signals according to its supported constellations and receiver design | GNSS standards and receiver/equipment evidence |
| SBAS broadcast path | SBAS information is broadcast to users through SBAS signal channels described by the relevant source family | Annex 10 / DO-229 / service-provider source notes |
| SBAS GEO role | Some sources may describe SBAS GEO broadcast and, where supported by the standards/service context, ranging-related use | direct standards/service evidence before system-specific statements |
| Time reference | Time alignment is part of the navigation/correction problem | Annex 10 / DO-229 / service-definition evidence before numerical claims |
| Receiver use | The airborne/user receiver combines measurements and SBAS data according to its approval basis | receiver standards, avionics, aircraft, and operator evidence |
Blocked claim patterns
Do not infer:
- that SBAS broadcast reception proves a receiver may use it for a procedure;
- that a GEO broadcast path always creates an operational ranging source;
- that a generic time-reference statement proves a numerical timing tolerance;
- that service-provider architecture proves aircraft or operator authorization;
- that one SBAS system’s signal role applies to another system without source-specific support.
Safe wording pattern
The source supports a concept-level statement about ranging or time-reference context within its own scope. It does not by itself establish receiver approval, procedure availability, or operational authorization.Source anchors
- SBAS Core Claim Routing
- SBAS Architecture
- SBAS Signal and Message Flow
- SBAS Ground Segment and Airborne Receiver Responsibilities
- Source - ICAO Annex 10 Volume I GNSS SBAS
- Source - RTCA DO-229
- Source - SBAS Service Providers