Source evaluation: the Admiralty code, corroboration and circular reporting
Source evaluation grades reliability and credibility separately using the NATO Admiralty code: letters A to F rate the source's track record and access, numbers 1 to 6 rate whether the specific item is confirmed by independent sources. An item is only corroborated when the supporting reports have genuinely independent origins.
An assessment is only as auditable as its provenance record. Grading sources takes seconds and prevents the most damaging class of error: treating amplification as corroboration.
- Grade the source (A-F) and the item (1-6) independently.
- Trace every republished claim to its original publisher before counting it as corroboration.
- Record URL, publisher, publication date and retrieval time for every item.
- Never accept a publication date later than the report generation time.
- Label model-generated context as analysis, never as a source.
The Admiralty scale
Reliability of the source:
- A — completely reliable; long consistent history
- B — usually reliable; minor doubts
- C — fairly reliable
- D — not usually reliable
- E — unreliable
- F — reliability cannot be judged
Credibility of the information
Rated on the specific item, independently of who reported it:
- 1 — confirmed by independent sources
- 2 — probably true
- 3 — possibly true
- 4 — doubtful
- 5 — improbable
- 6 — cannot be judged
Circular reporting
Circular reporting occurs when one origin is echoed by several outlets and the echoes are counted as independent confirmation. In open-source work this is the norm rather than the exception: agency wires, aggregator sites and social reposts collapse into a single origin. Trace the chain before upgrading credibility.
Provenance discipline in practice
Store the retrieval time alongside the publication date, keep the canonical URL rather than a share link, and mark any item you could not re-verify. Provenance is what allows a reader — or an auditor after an incident — to reconstruct the basis of a decision.
Frequently asked questions
- What is the Admiralty code?
- The Admiralty code, also called the NATO system, is a two-part rating that grades source reliability from A to F and information credibility from 1 to 6, so that a report labelled B2 signals a usually reliable source carrying probably true information.
- What is circular reporting?
- Circular reporting is when a single original claim is republished by multiple outlets and mistaken for independent corroboration. It artificially inflates credibility ratings and is the most common source-evaluation error in open-source intelligence.
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