Glossary
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TermDefinition
- General Nautical Terminology IALA
The International Association of Lighthouse Authorities (IALA) is an international organisation that aims to promote safe, efficient, and...
More Details - General Nautical Terminology ICC
An official document that certifies a person's ability to operate a pleasure craft in countries that recognise it.
The International...
More Details - Flag / Pennant, Signals & Communication Code Flag India (I)

The International Maritime Signal Flag India.
Meaning
I am altering course to port.
- General Nautical Terminology, Weather (Meteorology) ICON
A numerical weather prediction model that uses a grid system based on an icosahedron to simulate atmospheric processes with high resolution and...
More Details - General Nautical Terminology, Weather (Meteorology) ICOsahedral Nonhydrostatic model (ICON)
A numerical weather prediction model that uses a grid system based on an icosahedron to simulate atmospheric processes with high resolution and...
More Details - Flag / Pennant, General Nautical Terminology, Signals & Communication ICS
A system of flags, codes, and symbols used by ships to communicate essential messages and ensure safety at sea, regardless of language...
More Details - Did you know?, General Nautical Terminology, Navigation IDL
An imaginary longitudinal line located at approximately 180 degrees longitude serving as the demarcation where the calendar date changes by one...
More Details - General Nautical Terminology, Navigation IHO
An intergovernmental organisation dedicated to ensuring the uniformity and standardisation of hydrographic and nautical charting practices...
More Details - Flag Semaphore, Signals & Communication Letter I (Flag Semaphore)

This shape represents the Letter I (Flag Semaphore) and the Number 9 (Flag Semaphore).
- Morse Code, Signals & Communication Letter I (Morse Code)
International Morse Code sequence representing the letter I.
- Organisation IMO
A specialised agency of the United Nations headquartered in London and responsible for regulating shipping, the IMO has 175 Member States.
The...
More Details - General Nautical Terminology Impeller
An impeller is a rotating component within a pump or compressor that is used to impart motion to a fluid. It typically consists of blades or...
More Details - Courses, RYA Improve your WingsurfingThe RYA Improve Your Wingsurfing course is aimed at wingsurfers who want to refine their skills and gain more control. Participants learn advanced... More Details
- Phonetic Alphabet, Signals & Communication India
Pronounced: IN-dee-ah
The term for the letter I in the NATO Phonetic Alphabet.
- General Nautical Terminology In Hauler
A line or tackle used to pull a sail or spar inboard, typically to adjust sail shape or reduce projection beyond the hull.
An in hauler is a...
More Details - General Nautical Terminology In Irons
A situation where a sailing vessel is stalled with its bow pointed directly into the wind, making it difficult to manoeuvre or gain forward...
More Details - Courses, RYA Inland Waterways CrewThe RYA Inland Waterways Crew course provides essential training for assisting with operations on canals, rivers, and other inland waterways.... More Details
- Courses, RYA Inland Waterways Helmsman'sThe RYA Inland Waterways Helmsman’s course is designed for those operating boats on canals and rivers. This two-day course covers boat handling,... More Details
- General Nautical Terminology, Safety INMARSAT
A global satellite communications organisation providing maritime, aviation, and land-based services for safety and operational...
More Details - General Nautical Terminology Inshore
The area of water close to the shore, typically within a few miles, where vessels operate in relatively calmer and shallower waters compared to...
More Details - General Nautical Terminology In StaysWhen the bow points directly into the wind with the sails flapping during the process of going about
- Courses, RYA Intermediate WindsurfingThe RYA Intermediate Windsurfing course bridges the gap between beginner and advanced skills. Participants learn techniques for improving speed,... More Details
- Courses, RYA Intermediate Windsurfing (Planing)The RYA Intermediate Windsurfing (Planing) course introduces participants to planing techniques, enabling them to harness the power of stronger... More Details
- General Nautical Terminology International Association of Lighthouse Authorities (IALA)
The International Association of Lighthouse Authorities (IALA) is an international organisation that aims to promote safe, efficient, and...
More Details - General Nautical Terminology International Certificate of Competence (ICC)
An official document that certifies a person's ability to operate a pleasure craft in countries that recognise it.
The International...
More Details - Flag / Pennant, General Nautical Terminology, Signals & Communication International Code of Signals (ICS)
A system of flags, codes, and symbols used by ships to communicate essential messages and ensure safety at sea, regardless of language...
More Details - General Nautical Terminology International Convention for the Prevention of Pollution from Ships (MARPOL)
Established by the IMO, MARPOL is the convention for preventing pollution from ships. It is the main international convention covering the...
More Details - Did you know?, General Nautical Terminology, Navigation International Date Line (IDL)
An imaginary longitudinal line located at approximately 180 degrees longitude serving as the demarcation where the calendar date changes by one...
More Details - General Nautical Terminology, Navigation International Hydrographic Organization (IHO)
An intergovernmental organisation dedicated to ensuring the uniformity and standardisation of hydrographic and nautical charting practices...
More Details - Organisation International Maritime Organisation (IMO)
A specialised agency of the United Nations headquartered in London and responsible for regulating shipping, the IMO has 175 Member States.
The...
More Details - General Nautical Terminology, Safety International Maritime Satellite Organisation (INMARSAT)
A global satellite communications organisation providing maritime, aviation, and land-based services for safety and operational...
More Details - Flag / Pennant, Signals & Communication International Maritime Signal Flags
A system of flags ships use to communicate messages, signals, or important information visually. Flags often represent letters, numbers, or...
More Details - Did you know?, Navigation International Meridian Conference
A diplomatic meeting held in 1884 in Washington, D.C., where representatives from 25 nations convened to establish a standard prime meridian for...
More Details - Morse Code, Signals & Communication International Morse Code
A standardised system of encoding text characters as sequences of dots (short signals) and dashes (long signals) used for communication,...
More Details - General Nautical Terminology International Regulations for Preventing Collisions at Sea (IRPCS)
- Organisation, Signals & Communication International Telecommunication Union (ITU)
A specialised agency of the United Nations responsible for coordinating global telecommunication operations and services, including radio...
More Details - General Nautical Terminology, Weather (Meteorology) Irish Sea
Sea area of the Met Office Shipping Forecast. Covers the Irish Sea between Ireland and Great Britain.
Between Ireland and Great Britain, the...
More Details - General Nautical Terminology IRPCS
- Organisation ISAF
World Sailing, formerly known as the International Sailing Federation (ISAF), is the governing body for the sport of sailing...
More Details - Light Characteristic Iso
A light where the duration of light and darkness are equal.
Isophase describes a navigational aid that emits a light signal with equal periods...
More Details - General Nautical Terminology IsobarOn a synoptic chart, a line joining points of equal pressure
- General Nautical Terminology Isolated Danger Mark
Buoy or pillar positioned on a dangerous underwater obstruction.

An isolated danger mark is a navigation aid used at sea to indicate a...
More Details - Light Characteristic Isophase (Iso)
A light where the duration of light and darkness are equal.
Isophase describes a navigational aid that emits a light signal with equal periods...
More Details - Organisation, Signals & Communication ITU
A specialised agency of the United Nations responsible for coordinating global telecommunication operations and services, including radio...
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