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Day shapes: forms communicating states

Ball, cone, diamond and cylinder have meaning within specific arrangements.

8 min read
Manual contents
In this guide
Six selected states: one anchor ball; down-pointing sail-with-propulsion cone; two not-under-command balls; three vertical aground balls; restricted-ability ball-diamond-ball; fishing cones with apexes together. Rules and exceptions are in the text.
Shapes and arrangements

Original recognition schematic, not to scale; not navigation instruction.

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Six selected states: one anchor ball; down-pointing sail-with-propulsion cone; two not-under-command balls; three vertical aground balls; restricted-ability ball-diamond-ball; fishing cones with apexes together. Rules and exceptions are in the text.

A day shape is a prescribed form observed by day. Shapes include balls, cones, cylinders and diamonds; Portuguese RIEAM often uses balões for these forms.

They are neither buoyage marks nor manufacturer decoration. Black colour, shape, arrangement and the state referred to belong to the message.

The figure compares selected states without installation dimensions, heights, separation or implying that a partial arrangement is sufficient. Recognising one form is a beginning; the complete arrangement and applicable condition determine what it communicates.

Annex I: form and conformity

Annex I contains technical requirements for shapes, dimensions and separation. A diamond consists of two cones sharing a base, rather than simply a rotated square flag.

Vessels under 20 metres have proportionate-size provisions, but these do not authorise omitting a shape required by another rule. Construction and installation relate to the competent authority.

This chapter’s drawings are recognition schematics rather than templates or demonstrations that a catalogue shape meets specifications. Size concessions and exemptions from carrying a signal are different questions.

Anchoring and grounding are different states

Rule 30(a) associates a ball with anchoring. For a vessel aground, paragraph (d)(ii) requires three balls in a vertical line, not an anchoring ball plus three further balls.

Paragraph (d)(i) adds two all-round red lights to the applicable anchor lights. Exceptions have defined subjects and conditions: below 7 metres at anchor, paragraph (e) additionally requires being outside specified channel, fairway, anchorage or normal-navigation locations; below 12 metres aground, (f) addresses the additional signals of (d)(i) and (ii).

“Small boats do not use shapes” is therefore inaccurate. Location, state and length must accompany the statement, rather than one length number being extracted as a blanket exemption.

Sail with propulsion and towing

Under Rule 25(e), proceeding under sail while also mechanically propelled requires a forward cone, apex down, where best seen. Rule 24 includes diamonds for specified towing conditions; tow length differs from tug length, and the 200-metre threshold uses its defined measurement.

Additional provisions cover inconspicuous or partly submerged objects. Seeing a cone or diamond without context does not justify inventing activity, passing side or unobserved extent.

The signalling purpose is specific, and an individual hull’s commercial description does not override its actual operation.

Fishing, not under command and restricted work

Rule 26 uses two cones with apexes together for fishing, both trawling and other fishing, with additional signals for outlying gear under specified conditions. Rule 27(a) identifies not under command through two balls; (b) uses ball, diamond, ball for restricted ability to manoeuvre.

These statuses differ: exceptional circumstance and nature of work are distinct under Rule 3. Mine clearance has its own three-ball arrangement, while dredging or underwater work adds obstruction and passing-side indications.

An incomplete distant view must not be interpreted as the complete arrangement or a guaranteed corridor.

A draught-constrained vessel may show a cylinder under Rule 28. Not every deep-draught hull has that status: available depth and width and severe restriction on deviation belong to the definition.

Rule 29 pilotage refers to anchor shapes when anchored in addition to its lights, rather than creating a general geometric priority shape. The rigid Code flag A for diving has its own Rule 27(e) conditions and should not automatically be equated with other recreational diving flags.

Each symbol belongs to an identified normative provision and situation.

The concept in a few words

Day shape

A prescribed daytime form whose meaning depends on shape, arrangement and state under Part C and Annex I.

Educational definition; consult the scope of the identified rule.

Sources and references

  1. RIEAM / COLREGs — Rule 28: Vessels constrained by their draught ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 28, normative Portuguese printed p.48 (PDF p.54); International English cross-check in USCG handbook.

    Rule 28; IH normative Portuguese printed p.48, PDF p.54; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  2. RIEAM / COLREGs — Rule 25: Sailing vessels underway and vessels under oars ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 25, normative Portuguese printed p.39 (PDF p.45); International English cross-check in USCG handbook.

    Rule 25; IH normative Portuguese printed p.39, PDF p.45; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  3. RIEAM / COLREGs — Rule 26: Fishing vessels ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 26, normative Portuguese printed p.40 (PDF p.46); International English cross-check in USCG handbook.

    Rule 26; IH normative Portuguese printed p.40, PDF p.46; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  4. RIEAM / COLREGs — Rule 20: Application of lights and shapes ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 20, normative Portuguese printed p.29 (PDF p.35); International English cross-check in USCG handbook.

    Rule 20; IH normative Portuguese printed p.29, PDF p.35; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  5. RIEAM / COLREGs — Rule 2: Responsibility ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 3, normative Portuguese printed p.3 (PDF p.9); International English cross-check in USCG handbook.

    Rule 3; IH normative Portuguese printed p.3, PDF p.9; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  6. COLREGs Annex I — Positioning and technical details of lights and shapes ↗

    Instituto Hidrográfico / International Maritime Organization · Annex I; printed p.65, PDF p.71; International cross-check USCG.

    Annex I, IH printed p.65 (PDF p.71); cross-check International annex in USCG handbook. Installation/approval is not taught. International/Inland distinction checked in the USCG PDF: International §3(a) half-length/100m agrees with IH; the quarter-length/50m value belongs to U.S. Inland and is not imported. No dimensional installation prescription is reproduced.

    Checked on
  7. RIEAM / COLREGs — Rule 27: Vessels not under command or restricted in their ability to manoeuvre ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 27, normative Portuguese printed p.43 (PDF p.49); International English cross-check in USCG handbook.

    Rule 27; IH normative Portuguese printed p.43, PDF p.49; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  8. RIEAM / COLREGs — Rule 29: Pilot vessels ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 29, normative Portuguese printed p.49 (PDF p.55); International English cross-check in USCG handbook. Rule 30, normative Portuguese printed p.49 (PDF p.55); International English cross-check in USCG handbook.

    Rule 29; IH normative Portuguese printed p.49, PDF p.55; English International column cross-check. Individual provision commencement not established: valid_from remains null. Rule 30; IH normative Portuguese printed p.49, PDF p.55; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on
  9. RIEAM / COLREGs — Rule 24: Towing and pushing ↗

    Instituto Hidrográfico / International Maritime Organization · Rule 24, normative Portuguese printed p.34 (PDF p.40); International English cross-check in USCG handbook.

    Rule 24; IH normative Portuguese printed p.34, PDF p.40; English International column cross-check. Individual provision commencement not established: valid_from remains null.

    Checked on

Regulatory references

Keep discovering

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Navigation lights: sector, function and state Responsibilities: keeping course also has limits

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