A lateral mark is a buoy or fixed beacon that defines the boundary of a navigable channel. According to the IALA (International Association of Marine Aids to Navigation and Lighthouse Authorities) system, these marks tell a mariner which side to leave them on when following the conventional direction of buoyage – usually upstream in rivers or into a harbour from seaward. The world is divided into two regions: IALA Region A (Europe, Africa, most of Asia) and Region B (the Americas, Japan, Philippines). In Region A, red cylindrical port marks are left to port (left) when entering a harbour, while green conical starboard marks are left to starboard. In Region B the colours are reversed. Knowing your region is essential; mistaking a port mark for a starboard mark can ground a vessel. A traditional way to verify your position relative to a mark is to take a compass bearing and cross-check with the chart – a technique thoroughly covered in our article on how to use a marine compass. For a broader view of all navigation aids, including electronic systems that complement lateral marks, explore the Navigation tag.
Quick answers
What is Lateral mark?
A sea mark used in the IALA Maritime Buoyage System to indicate the port or starboard edge of a channel relative to the direction of buoyage.
What is Lateral mark used for on a yacht?
Before entering a port, identify the local IALA region and confirm the direction of buoyage from the chart. In Region A, remember 'red left returning' (i.e. keep red marks to port when coming from sea). Always cross-check visually with the chart and use a compass bearing to avoid confusion.
What topics are related to Lateral mark?
Sources and verification
- Navi.training: GPS, AIS и радар. — «Три глаза» вашей яхты — знаете ли вы, в чём разница?
- Navi.training: Как работает GPS, и роль электронной навигации в мире яхтинга
- Navi.training: Компас на яхте: Как пользоваться морским компасом и для чего он нужен яхтсменам?
- Navi.training: GPS, AIS та радар. — «Три ока» вашої яхти — чи знаєте ви, в чому різниця?
- Navi.training: Як працює GPS та роль електронної навігації у світі яхтингу
- Navi.training: Компас на яхті: Як користуватися морським компасом і для чого він потрібен яхтсменам?
- Navi.training: GPS vs AIS vs Radar on a Yacht: What Each System Really Does
- Navi.training: How GPS Works and the Role of Electronic Navigation in the World of Sailing
- Navi.training: The Compass on a Sailboat: How to Use a Marine Compass and Why Sailors Need It
- Wikipedia: Lateral mark · CC BY-SA 4.0 / GFDL
27 min to read 
