What Are Lateral Marks?
Ships don’t always navigate the high seas. They often navigate narrower waters, such as rivers and canals, and near ports or harbors, encountering shallow areas in deltas and estuaries. In other words, a key aspect of navigation is the application of restrictive conditions, which require ships to adhere to specific limitations.
These restrictions mean that seafarers or navigators cannot operate their ships completely freely on their own, as many areas may be un navigable and prohibited.
These areas may be designated as unnavigable for several reasons:
- Water depth conditions (and therefore the available low draft) due to proximity to the coast do not allow the ship to navigate safely, as the shallow depths pose a significant risk of grounding and underwater hull damage.
- Unsuitable underwater terrain and topological constraints.
- Hydrodynamic problems that are unsuitable for ship navigation, such as unfavorable wave breaking and tidal behavior, unfavorable flow patterns, eddies, currents, etc.
- Traffic from other ships (e.g., near ports).
- The presence of structures such as bridges, dams, submarine cables, and offshore wind farms in prohibited routes.
- Environmental restrictions, such as natural habitats and environmentally sensitive areas, should be avoided.
- Areas near residential areas or population centers, and waters used for fishing and aquaculture.
- Entry is prohibited if there are economic, commercial, defense, government, or other facilities on or near the shore that require a certain boundary of the surrounding waters.
- Entry is also prohibited if there are any other potential hazards or risks within the designated area.
Lateral Marks
For this reason, when ocean-going vessels enter restricted waters, or vice versa, they are generally required to follow a prescribed route. For the same purpose, transverse marking systems are also used to assist with maritime navigation, helping to identify the boundaries where a vessel must remain and not deviate from its course.
These markings are often used in long-distance navigation, such as signs and indicators that help pilots identify traffic on busy roads, or lighting and unique marking systems on runways or taxiways used to guide aircraft.
Transverse marking systems are used to demarcate specific areas, except in rare circumstances when a designated route needs to be changed for some reason. Transverse markings in specific areas follow a particular pattern that seafarers or navigators must be familiar with.
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These transverse markings not only mark the boundaries of navigation routes but also represent a path to guide ships in a designated direction toward their destination. When a ship enters restricted waters from the ocean and intends to sail, this direction is called the conventional buoyancy direction. It may also be the opposite direction.
Transverse markings for specific areas are limited to the ship’s coast, i.e., the port side, and are marked differently from starboard markings. For any ship navigating a designated route within a restricted area, a port marking indicates the ship’s port side, or, as a convention, the port side when viewed along its course, and must be on the starboard side. Similarly, a port marking indicates that the port side must always be to the left of the marking (or, the port marking must be to the starboard of the port side).
Now, when a ship returns to open waters from a restricted area, such as when returning from an inland waterway to the open ocean, the markings are reversed. Since the ship is now heading in the opposite direction from when it originally entered the restricted area, i.e., against the current, as a convention, the markings that previously signaled port now serve as indicators of starboard, and vice versa.
Marking System
How do we distinguish between port and starboard markings for different routes? This convention was developed by the International Maritime Safety Association (IALA) and is tailored to specific areas of application. These areas are divided into the following categories:
Zone A: Europe, Africa, Asia (excluding Japan and South Korea), and southern countries such as Australia.
Zone B: The Americas, Japan, South Korea, the Philippines, Taiwan, etc.
In Zone A, all port signs (markers placed on the port side of a ship) are red. These signs come in various shapes, such as cylinders, masts, boxes, columns, and cones, and typically feature a series of flashing odd numbers, such as 1, 3, and 5.
These shapes may also feature a box-shaped, cube-shaped projection at the top. To facilitate night vision, they are equipped with a red top light that can flash in any pattern except a “2+1” rhythm (two rapid flashes followed by one flash).
Starboard shapes, indicating that the vessel’s starboard side must remain to the left of the shape, are similar in shape but are green in color. However, they follow a pattern of increasing even numbers, such as 2, 4, 6, and so on.
Their green illumination follows a similar pattern. Furthermore, the top light at the top of the shape is a pointed arrow, unlike the port cube.
Navigation Shapes
Shipways often fork, requiring a vessel to turn. The fork is marked by a different sign, indicating a headland or point separating land. The vessel must turn to reach that point and proceed in the desired direction.
If a vessel needs to change course to starboard, known as a starboard turn (technically known as the starboard priority channel), the sign is green and red with a green stripe in the middle. When turning right onto the starboard priority channel or route, the sign must be on the vessel’s port side. The top light is red, identical to the normal port beacon, and the flashing pattern is the same.
Similarly, when a vessel needs to turn left (i.e., proceed to the left), the sign is a similar striped sign, but with a red stripe down the middle. After turning left, this modified sign must be on the starboard or right side of the vessel. Therefore, in terms of its other characteristics, it follows the same pattern as the normal starboard beacon, with a sharp green or arrow-shaped top and flashing green light.
For vessels returning to their original course, navigators or mariners must observe the signs in reverse order. For Class B areas, the order of the signs is exactly reversed. When a vessel enters an inland waterway from deep water, the port sign is green (odd numbers), while the starboard sign is red (even numbers). However, the top shape (cubic for port, conical for starboard) remains the same. Therefore, the port sign flashes green, while the starboard sign flashes red.
The modified signs also differ for crossing or crossing routes for vessels navigating inland or against the current. When a vessel needs to turn right, maintaining the mark to starboard, a red light band is positioned between the green and red lines, unlike the Zone A system (where the green light band is positioned in the center of the mark).
The flashing light is green. Similarly, when a vessel turns from port or harbour to the channel or fairway (with starboard towards the dividing line), the green light band is positioned in the center. A flashing red light with the same pattern is located at the top.
