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Learn/Buoyage and Signals/Lights, rhythms and light characteristics

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Published without technical review · version 3 ·

Incomplete recognition: what an observation has not resolved

One colour, silhouette or white light can leave several hypotheses open.

9 min read
Manual contents
In this guide

Seeing part of a mark is not the same as identifying it. A white light can belong to several categories; a silhouette can hide colour; a topmark may be unresolved.

The useful approach is to organise observations by attribute: what is known, what is missing and which information would distinguish hypotheses. An incomplete description then remains useful instead of becoming an invented certainty.

First panel: an observed white light leaves cardinal, isolated-danger and safe-water hypotheses open, without identification. Second: yellow body with unresolved topmark. Third separates a special diagonal X and an upright emergency cross, with correct technical colours and no invented local purpose.
Observation is not identity

Original conceptual schematic, not to scale; fictional cases, not a manoeuvre procedure.

insideSailOriginal insideSail artwork — all rights reserved
Enlarge the diagram
First panel: an observed white light leaves cardinal, isolated-danger and safe-water hypotheses open, without identification. Second: yellow body with unresolved topmark. Third separates a special diagonal X and an upright emergency cross, with correct technical colours and no invented local purpose.

An identity combines several pieces

Daytime appearance combines colour, shape and topmark. At night, light colour and characteristic become particularly important.

Identification, published position and authority description help connect those pieces with a particular aid. Not every attribute will be available in every observation: a topmark may be obscured or beyond visual resolution, and some provisions allow it to be absent.

Writing “unresolved” differs from writing “does not exist”.

Worked case: two white flashes

InformationSupported conclusionStill unresolved
White lightObserved colourMark category
Two illuminated momentsCount within the windowComplete group or fragment
No recorded repetitionPeriod unknownInterval to the next cycle
Topmark unresolvedObservation limitationTopmark present, absent or obscured

An isolated-danger mark uses a white two-flash group where fitted, but two observed flashes do not establish that characteristic by themselves. They may be part of a longer sequence.

A cardinal also uses white, organised as Q or VQ; a safe-water mark uses other white characteristics. The useful question is “did we observe a complete cycle from one identified source?”

before choosing a category name.

  1. Transcribe the observation without adding missing attributes.
  2. List hypotheses compatible with the fragment without inventing probabilities.
  3. Identify distinguishing information: a complete cycle, topmark, body bands and documentary correspondence.
  4. When new evidence becomes available, add its origin and date. Retain the initial observation as partial.

Worked case: yellow alone is insufficient

Another fictional note reads “yellow body; topmark unresolved”. A special mark is a hypothesis, but its local purpose remains unknown.

Later adding a yellow X and a documented characteristic gives the identification more support. Its function may concern a recreational area, an installation or another published use; colour does not select between those purposes.

Understanding the purpose requires linking the mark with local information.

A special mark’s yellow X differs from the upright yellow cross of an emergency wreck-marking buoy. The latter adds vertical blue/yellow stripes and alternating blue/yellow light.

Calling both simply a “cross” loses the distinguishing orientation. Describe what the image shows: X, upright cross or orientation unresolved.

A mirrored or heavily stylised drawing can make silhouette-only identification insufficient.

Common confusions and key points

  • Confidence can differ by attribute: clear colour, unknown period.
  • Conical shape alone establishes neither region nor conventional direction.
  • A short illuminated interval does not prove a fixed light; a short dark interval does not prove failure.
  • Mark identity, local purpose and suitability of a passage are different questions.

The outcome is a better description rather than a more confident guess. Record resolved attributes and gaps separately.

The light-cycle lesson explains repetition; the position-and-fault lesson connects observations with official records and displays. In real use, current charts and the competent authority provide the context absent from these fragments.

Later information may confirm colour while correcting the proposed name. Separate fields allow that correction without erasing a valid observation.

This is how a record improves over time.

IALA R1001, edition 2.0, June 2023: 2.2–2.6 and Section 5 abbreviations. Portuguese RBMN: Articles 3 and 10–14, annex to Portaria 177/2016. The combinations studied retain their respective source context, without merging recommendation and national legislation. ↗

Sources and references

  1. RBMN — artigo 14: Boias de assinalamento de emergência ↗

    Diário da República · RBMN annex Article 14; printed p.1981, PDF p.4.

    Annex RBMN Article 14, published text 24 June 2016. Commencement follows Portaria Article5; later national interpretation/updates and local directions require qualified checking. Not treated as automatic adoption of IALA2023.

    Checked on
  2. IALA R1001 — Special marks and Mobile AtoN, exact edition context ↗

    IALA · Sections 2.5.1–2.5.2.6; PDF p.18 onwards; edition 2.0 June 2023.

    IALA recommendation, edition 2.0 June 2023, 2.5.1–2.5.2.6. Consulted edition does not establish individual national effective dates. Publication and jurisdiction require qualified review.

    Checked on
  3. IALA R1001 — Light rhythm identities and abbreviations ↗

    IALA · Sections 2.2.2, 2.2.4, 2.4.2.2, 2.6.2.1, 4 (definitions) and 5 (abbreviations); PDF p.13 onwards and p.29; edition 2.0 June 2023.

    IALA recommendation, edition 2.0 June 2023, 2.2.2, 2.2.4, 2.4.2.2, 2.6.2.1 and 4. Consulted edition does not establish individual national effective dates. Publication and jurisdiction require qualified review.

    Checked on
  4. IALA R1001 — Cardinal quadrants, topmarks, colours and light rhythms ↗

    IALA · Sections 2.2.1–2.2.4; PDF p.12 onwards; edition 2.0 June 2023.

    IALA recommendation, edition 2.0 June 2023, 2.2.1–2.2.4. Consulted edition does not establish individual national effective dates. Publication and jurisdiction require qualified review.

    Checked on
  5. RBMN — artigo 3: Método de caracterização das marcas ↗

    Diário da República · RBMN annex Article 3; printed p.1979, PDF p.2.

    Annex RBMN Article 3, published text 24 June 2016. Commencement follows Portaria Article5; later national interpretation/updates and local directions require qualified checking. Not treated as automatic adoption of IALA2023.

    Checked on
  6. IALA R1001 — Emergency wreck identity and other new-danger marking ↗

    IALA · Sections 2.6.1–2.6.2 and 3.2.2; PDF p.20 onwards; edition 2.0 June 2023.

    IALA recommendation, edition 2.0 June 2023, 2.6.1–2.6.2 and 3.2.2. Consulted edition does not establish individual national effective dates. Publication and jurisdiction require qualified review.

    Checked on
  7. IALA R1001 — Isolated danger and limits of inference about passing distance ↗

    IALA · Sections 2.3.1–2.3.2; PDF p.15 onwards; edition 2.0 June 2023.

    IALA recommendation, edition 2.0 June 2023, 2.3.1–2.3.2. Consulted edition does not establish individual national effective dates. Publication and jurisdiction require qualified review.

    Checked on
  8. IALA R1001 — Safe water identity, uses and light alternatives ↗

    IALA · Sections 2.4.1–2.4.2; PDF p.17 onwards; edition 2.0 June 2023.

    IALA recommendation, edition 2.0 June 2023, 2.4.1–2.4.2. Consulted edition does not establish individual national effective dates. Publication and jurisdiction require qualified review.

    Checked on
  9. RBMN — artigo 8: Quadrantes das marcas cardeais ↗

    Diário da República · RBMN annex Article 10; printed p.1980, PDF p.3. RBMN annex Article 11; printed p.1980, PDF p.3. RBMN annex Article 12; printed p.1980, PDF p.3. RBMN annex Article 13; printed pp.1980–1981, PDF pp.3–4.

    Annex RBMN Article 10, published text 24 June 2016. Commencement follows Portaria Article5; later national interpretation/updates and local directions require qualified checking. Not treated as automatic adoption of IALA2023. Annex RBMN Article 11, published text 24 June 2016. Commencement follows Portaria Article5; later national interpretation/updates and local directions require qualified checking. Not treated as automatic adoption of IALA2023. Annex RBMN Article 12, published text 24 June 2016. Commencement follows Portaria Article5; later national interpretation/updates and local directions require qualified checking. Not treated as automatic adoption of IALA2023. Annex RBMN Article 13, published text 24 June 2016. Commencement follows Portaria Article5; later national interpretation/updates and local directions require qualified checking. Not treated as automatic adoption of IALA2023.

    Checked on

Regulatory references

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The next piece of the puzzle

Light period Isolated danger mark Special mark

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