Special marks: yellow calls for the published purpose

A special mark identifies an area or feature whose nature can be found in the chart or another nautical publication. Yellow identifies the family; it does not alone distinguish a recreation area, submarine cable, aquaculture or another purpose.

It is like recognising an information sign before reading its content: the category points to published information rather than conveying one identical rule everywhere.

The X topmark is preferably three-dimensional so it can be recognised from different directions. Body shape should not conflict with laterals: R1001 gives the example of a special mark on a channel’s port side, which may be cylindrical but not conical.

This does not turn every yellow can into a universal port-hand indication. The relationship depends on the particular use and channel reference.

The family can mark oceanographic data systems, military exercise zones, spoil grounds, cables or pipelines, recreation areas, anchorage boundaries, structures and aquaculture. These uses do not share one access regime.

Yellow alone creates neither an entry prohibition, anchoring permission nor permission to attach a boat. Numbers, lettering or pictograms can help identify purpose, but meaning belongs to the authority and relevant documents.

Generally, a special mark does not replace laterals or cardinals where those families suit channel limits or obstructions. Particular applications exist: a dredged channel for deep-draught vessels can use special marks within an area adequately deep for general navigation.

Laterals or cardinals continue to define general navigation limits. These are two information layers rather than competing recommendations about one passing side.

An ordinary special mark does not use rhythms reserved for cardinals, isolated danger, safe water or MAtoN under R1001 2023. This separation reduces confusion between yellow and white under difficult observation.

It does not mean “any rhythm”: the individual characteristic still needs a description. The MAtoN reservation retains its 2023 recommendation scope here, without being inserted into the original Portuguese 2016 text.

The 2023 R1001 edition includes MAtoN: a special mark attached to a floating object that may create a collision hazard. Its defined characteristic combines three flickering phases with two regular flashes; it is not simply Fl(5).

This variant needs its own description and should not be assigned to every yellow special mark. Portuguese RBMN 2016 sets out special uses and characteristics in Article 13; a category detailed in a later recommendation is not presumed automatically added to the national act.

An editorial record can separate “type: special”, “characteristics: yellow and X topmark” and “purpose: aquaculture area”. The last field needs a reference for the place.

Knowing only the first two still allows the family to be explained while purpose remains unknown. This structure allows two cases to be compared without giving an oceanographic mark the regime of an exercise area.

Purpose is therefore an explicit field, rather than a hidden assumption attached to the colour.