Maritime Signal Flags

These flags are used at sea for communication between ships. They can
spell out short messages, and individual flags and various combinations
of flags also have special meanings. On ceremonial and festive occasions
the signal flags are used to ‘dress’ (decorate) ships.

This signalling system was drafted in 1855 and published in 1857, and
was gradually adopted by most seafaring countries. It was revised in 1932.

Usage

One-flag signals are urgent or very common signals (see meanings below)
Two-flag signals are mostly distress and maneuvering signals
Three-flag signals are for points of the compass, relative bearings,
standard times, verbs, punctuation, also general code and decode signals
Four-flags are used for geographical signals, names of ships, bearings, etc
Five-flag signals are those relating to time and position
Six-flag signals are used when necessary to indicate north or south or
east or west in latitude and longitude signals
Seven-flags are for longitude signals containing more than one hundred degrees.

International Maritime Signal Flags