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Chart Symbols

Chart Datum

is the lowest level from which charted depths, drying heights and tidal heights are measured. It is approximately equal to the lowest astronomical tide. Occasionally a very low tide will fall below chart datum.

Bathing Area

The symbols denote two yellow can buoys. They have no top marks and no lights. The chart shows that they mark the outer limit of a designated Bathing Area.

Port Lateral Buoy

The symbol with the letter R denotes a red can buoy, a lateral mark for the channel. Drawn at an angle indicates it is affected by the tide. The magenta teardrop indicates it has a light. The marked light sequence is a single red flash every 5 seconds.

South Cardinal

The symbols denote a pillar buoy with standard south cardinal markings (yellow over black). The marked light sequence is 6 (very quick) flashes in a group followed by a single long flash of a white light.

Starboard Lateral

The symbols denote a conical buoy of a lateral mark for the channel. The magenta teardrop indicates it has a light. The marked light sequence is a single green flash every 5 seconds.

Isolated Danger Mark

The symbols denote a pillar buoy with standard isolated danger markings (black with a red band). The marked light sequence is a group of 2 short flashes of a white light every 5 seconds.

Restricted Area

Areas with restrictions are marked on charts. In this area you cannot fish or anchor.

Safe Water Mark

The symbols denote a pillar buoy with standard safe water markings (red and white stripes). The marked light sequence is a 10-second isophase (this means 5 seconds of light and 5 seconds of dark in a 10 second period).

North Cardinal

The symbols denote a pillar buoy with standard north cardinal markings (black over yellow). The marked light sequence is a group continuous very quick flashing of a white light.

East Cardinal

The symbols denote a pillar buoy with standard east cardinal markings (black yellow black). The marked light sequence is 3 (very quick) flashes every 5 seconds of a white light.

West Cardinal

The symbols denote a pillar buoy with standard west cardinal markings (yellow black yellow). The marked light sequence is a group of 9 quick flashes every 15 seconds.

Direction of Buoyage

This arrow indicates the direction of buoyage. When travelling the same direction as the arrow, port buoys will be to port and starboard buoys to starboard.

Isolated Underwater Rock

It never uncovers but is considered a danger to shipping.

Shipping Lanes

Shipping lanes: be especially alert near shipping lanes and wherever possible cross them at right angles.