Introduction to Navigation

Navigation is the foundation of safe and effective seamanship. It combines theory and practice to ensure a vessel can determine its position, plot a safe course, and avoid danger while making efficient progress from one point to another. At its core, navigation at sea is about applying basic principles — understanding the compass, charts, tides, buoyage, and the Rules of the Road — before progressing to more advanced techniques such as fixing positions, course corrections, and voyage planning. This section provides a general overview of these essentials, giving you the building blocks needed to develop into a competent navigator. By mastering these fundamentals, you will be prepared to tackle both classroom exercises and the real-world challenges of navigating at sea.

Basic Sea Terms

 

Before learning how to navigate, you must know the correct terms used on board a vessel:

  • Bow – the front of the ship.

  • Stern – the back of the ship.

  • Port – the left-hand side of the ship when facing forward.

  • Starboard – the right-hand side of the ship when facing forward.

  • Ahead – in front of the vessel.

  • Astern – behind the vessel.

  • Beam – the widest point of the ship, or directly out to the side.

  • Draft – the depth of water a vessel needs to float.

 

Position and Direction

 

The first rule of navigation is always knowing your position. Today, GPS provides instant accuracy, but traditional methods such as bearings, dead reckoning, and even celestial navigation remain important backup skills. You never know what's going to break! 

Direction is determined by the compass. The two main types you will find are:

  • Magnetic Compass – points to magnetic north but is affected by deviation and variation.

  • Gyro Compass – points to true north and is often used on larger vessels. This is what is mainly used for navigation. 

 

Latitude and Longitude

 

The Earth is divided by an imaginary grid system called latitude and longitude, which allows navigators to give any position on the globe a set of coordinates.

  • Latitude measures how far north or south a place is from the Equator (0°).

    • It is expressed in degrees (°), minutes (′), and seconds (″).

    • The poles are at 90° North and 90° South.

    • Lines of latitude run east–west around the Earth but measure north–south distance.

  • Longitude measures how far east or west a place is from the Prime Meridian (0°) at Greenwich, England.

    • Also expressed in degrees, minutes, and seconds.

    • The maximum longitude is 180° East or 180° West.

    • Lines of longitude run north–south but measure east–west distance.

Together, latitude and longitude form a precise coordinate system. For example:

  • 50° 21′ N, 004° 08′ W is a position off the coast of Plymouth, UK.

 

Charts and Symbols

 

A nautical chart is the navigator’s map of the sea. It shows coastlines, water depths, hazards, and navigational aids. Learning to read and understand chart symbols is essential — from depth soundings to wreck marks and shipping channels.

Charts are used together with tools such as parallel rulers, dividers, and compasses to measure distance, plot bearings, and calculate positions.

 

Buoyage and Lights

 

Aids to navigation help mariners recognise safe water and avoid hazards. The most common system is the IALA buoyage system:

  • Port-hand marks – red, kept to port when entering a harbour.

  • Starboard-hand marks – green, kept to starboard when entering a harbour.

  • Cardinal marks – indicate the safest side to pass a danger (north, south, east, west).

  • Special marks – show areas such as anchorage grounds or traffic separation.

In addition, ships themselves display lights and shapes to indicate their status, such as underway, at anchor, or restricted in ability to manoeuvre.

 

Tides and Currents

 

The rise and fall of the tide, along with tidal streams and currents, have a direct effect on navigation. Tides determine whether there is enough water under the keel, while currents can set a vessel off course.

Navigators use tide tables to predict water levels and tidal stream atlases to plan for current strength and direction. Ignoring tides can lead to grounding or dangerous situations in coastal waters.

 

''Rules of the Road'' (COLREGS)

 

The International Regulations for Preventing Collisions at Sea (COLREGs) set out how vessels must behave to avoid collisions. Some key principles include:

  • Keep a proper lookout at all times.

  • Maintain a safe speed for the conditions.

  • Understand who is the stand-on vessel (keeps course and speed) and who is the give-way vessel (takes action to avoid collision).

  • Learn the rules for head-on, crossing, and overtaking situations.

Every navigator must know and apply these rules whenever on watch, this is the 'bread and butter'' of all navigators - so get Studying! 

 

Traditional and Modern Navigation

 

Modern ships use electronic systems such as GPS, radar, AIS, and ECDIS for navigation. These are powerful tools, but they are not foolproof. Power failures, system errors, or signal loss can occur.

That is why traditional methods — chartwork, compass bearings, and dead reckoning — remain essential skills. A good navigator is never reliant on electronics alone.