2.3 IALA Maritime Buoyage System (Region A) & Basic COLREGs Lights/Shapes

IALA Maritime Buoyage System (Region A) & Basic COLREGs Lights/Shapes

Navigating coastal approaches, estuaries, and harbor channels requires instant, error-free recognition of floating aids to navigation and vessel operational configurations. The International Organization for Marine Aids to Navigation (IALA) establishes the global standard for buoyage, while the International Regulations for Preventing Collisions at Sea (COLREGs) dictate the navigation lights and day shapes that vessels must display. For GP ratings preparing for DG Shipping examinations and bridge watchkeeping duties, mastery of Region A buoyage and COLREGs light/shape configurations is essential.

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1. The IALA Maritime Buoyage System: Region A vs. Region B

The IALA Buoyage System encompasses six distinct types of visual marks: Lateral Marks, Cardinal Marks, Isolated Danger Marks, Safe Water Marks, Special Marks, and Emergency Wreck Marking Buoys.

To reconcile historical maritime practices, IALA divided the globe into two distinct geographical regions:

• Region A: Encompasses India, Europe, Africa, Australia, New Zealand, the Middle East, and most of mainland Asia.
• Region B: Encompasses the Americas (North, Central, South), Japan, the Republic of Korea, and the Philippines.

The Conventional Direction of Buoyage

All lateral buoyage rules are defined with respect to the conventional direction of buoyage, which is:

1. Approaching a harbor, river, estuary, or waterway from seaward (entering from sea to port/harbor).
2. In open waters or channels without a clear sea approach, the direction follows the general clockwise circulation around continental landmasses (indicated by large magenta arrows on navigational charts).

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2. IALA Marks in Region A

                  REGION A: ENTERING FROM SEAWARD (INWARD BOUND)

          PORT HAND MARK                              STARBOARD HAND MARK
         +--------------+                            +-------------------+
         |  Color: RED  |                            |   Color: GREEN    |
         | Topmark: CAN |                            |  Topmark: CONE    |
         | Light: Red   |                            |  Light: Green     |
         +--------------+                            +-------------------+
                 \                                              /
                  \             FAIRWAY / CHANNEL              /
                   \==========================================/
                                      BOW
                                       |^
                                  [SHIP HULL]

1. Lateral Marks (Region A)

2. Preferred Channel (Bifurcation) Marks

Where a navigable channel divides into two routes, a preferred channel mark indicates which route is primary:

• Preferred Channel to Starboard (Leave mark to PORT):
  • Body: Red with one broad horizontal Green band across the center.
  • Topmark: Single red can (cylinder).
  • Light: Red light, composite group flashing: $\text{Fl}(2+1)\text{R}$.
• Preferred Channel to Port (Leave mark to STARBOARD):
  • Body: Green with one broad horizontal Red band across the center.
  • Topmark: Single green cone, point pointing upwards.
  • Light: Green light, composite group flashing: $\text{Fl}(2+1)\text{G}$.

3. Cardinal Marks

Cardinal marks indicate where the safest, deepest navigable water lies relative to the mark. They are named after the four primary compass quadrants: North, East, South, and West.

Seafarers memorize cardinal marks using the Clock-Face Mnemonic ($12, 3, 6, 9$ o'clock):

                                  NORTH CARDINAL
                              Topmark: Two Cones UP (▲ ▲)
                              Body: Black over Yellow
                              Light: Continuous Q or VQ (12 o'clock)
                                         |
                                         |
          WEST CARDINAL                  |                  EAST CARDINAL
      Topmark: Point-to-Point (▼ ▲)      |              Topmark: Base-to-Base (▲ ▼)
      Body: Yellow with Black band       +              Body: Black with Yellow band
      Light: Q(9) in 15s or VQ(9) in 10s |              Light: Q(3) in 10s or VQ(3) in 5s
      (9 o'clock)                        |              (3 o'clock)
                                         |
                                         |
                                  SOUTH CARDINAL
                             Topmark: Two Cones DOWN (▼ ▼)
                             Body: Yellow over Black
                             Light: Q(6) + LFl in 15s (6 o'clock + 1 long flash)

4. Other IALA Marks

• Isolated Danger Mark: Erected directly over or moored above a localized hazard (shoal, rock, wreck) surrounded by navigable water all around.
  • Body: Black with one or more broad horizontal Red bands.
  • Topmark: Two black spheres (balls) mounted vertically.
  • Light: White light, group flashing 2 flashes: $\text{Fl}(2)\text{W}$ (Mnemonic: 2 balls = 2 flashes).
• Safe Water Mark (Fairway / Mid-Channel Buoy): Indicates navigable water all around the mark (landfall mark, channel entrance centerline).
  • Body: Red and White vertical stripes.
  • Topmark: Single red sphere (ball).
  • Light: White light, Isophase (Iso), Occulting (Occ), Long Flash every 10 seconds ($\text{LFl }10\text{s}$), or Morse Code "A" (${\cdot}-$, dot-dash).
• Special Marks: Marks special operational zones (spoil grounds, pipeline/cable corridors, military firing ranges, recreation zones, oceanographic data buoys).
  • Body: Solid Yellow.
  • Topmark: Single yellow diagonal cross ('X').
  • Light: Yellow light, with a rhythm not reserved for cardinal, isolated danger, safe water or mobile aids to navigation (e.g., $\text{Fl Y}$, $\text{Fl}(4)\text{Y}$).
• Emergency Wreck Marking Buoy: Deployed immediately over newly discovered, unchartered wrecks or acute navigation hazards.
  • Body: Equal vertical stripes of Blue and Yellow.
  • Topmark: Standing upright yellow cross ('+').
  • Light: Alternating occulting Blue and Yellow light (1 second Blue, 0.5s dark, 1s Yellow, 0.5s dark).

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Flag Work and Required Single-Letter Signals

The national ensign identifies the ship’s flag State; a courtesy flag shows respect to a visited country, and a company flag identifies the operator. Prepare the correct flag and halyard, check that the line is clear and securely attached, hoist without fouling and secure the halyard. Hoist or dip the national ensign only as ordered; dipping means lowering and raising it as a salute. Follow the vessel’s flag instructions.

Report a signal promptly to the OOW. These code flags have their own meanings; identify COLREG lights and shapes separately.

3. Basic COLREGs Navigation Lights & Day Shapes

Part C of the COLREGs (Rules 20 through 31) specifies the lights displayed from sunset to sunrise and during restricted visibility, as well as day shapes displayed from sunrise to sunset.

Standard Light Arcs of Visibility (Rule 21)

                         COLREGs LIGHT ARCS OF VISIBILITY

                                  AHEAD (000°)
                                       |^
                    PORT SIDELIGHT     |     STARBOARD SIDELIGHT
                      RED LIGHT        |        GREEN LIGHT
                       112.5°          |          112.5°
                                \      |      /
                                 \     |     /
                        -------------------------------+--------------------
                       (From ahead to 22.5° abaft the beam on each side)
                                 /           \
                                /             \
                                      135°
                                   STERNLIGHT
                                  WHITE LIGHT
                                  ASTERN (180°)

  MASTHEAD LIGHT: Unbroken white light over 225° (from dead ahead to 22.5° abaft the beam on both sides)

1. Masthead Light: Unbroken white light placed over the fore-and-aft centerline, visible over an arc of $225^\circ$, from right ahead to $22.5^\circ$ (2 points) abaft the beam on either side.
2. Sidelights: A green light on the starboard side and a red light on the port side, each visible over an unbroken arc of $112.5^\circ$, from right ahead to $22.5^\circ$ abaft the beam on its respective side.
3. Sternlight: Unbroken white light placed near the stern, visible over an arc of $135^\circ$, shining $67.5^\circ$ (6 points) from right aft on each side.
4. Towing Light: Yellow light having the same arc of visibility as the sternlight ($135^\circ$).
5. All-Round Light: Visible continuously over the entire horizon of $360^\circ$.

Vessel Operational Categories & Required Displays