Basic requirements

• Visual aids to navigation should be sufficiently seen within required ranges.
• Certain features should be given to visual aids so that observers can clearly distinguish them from other lights.
• Intervals between flashes should be accurately repeated at a regular rate so as to be easily detected by mariners.
• Lanterns and light sources should be as efficient and reliable as possible.
• Visual aids should geographically conform to the usage and purpose of nautical aids as well as sufficient safety.

Types of Visual aids to navigation

Types		Descriptions
Lighthouse		It is a coastal tower equipped with a powerful lamp light designed for ships at sea to check the locations of land or other ships, or used to notify ships of the presence of ports, their entry point and more.
Light pole		The purpose of a light pole is the same as that of a lighthouse, but it has simple column structure with floating lights.
Beacon		It is located in a shallow sea or on a rock to indicate the presence of dangerous obstacles or the locations of sea routes to ships in nearby waters.
Illuminat light		It is a structure equipped with a projector that illuminates reefs or protrusions of breakwaters so as to inform ships of the presence of the obstacles.
Leading light		This tower type structure features a pair of lights separated by elevation-that is, one at a high location and the other at a low location. It is installed on land that is an extension to sea routes for the purpose of informing safe passages for vessels entering narrow channels, harbors or bay gates.
Directional		This tower type structure features green, white and red lights. It is installed on land that is an extension to sea routes for the purpose of informing safe passages for vessels entering narrow channels, harbors or bay gates. The area lit with white light indicates a safe sea course.
Light float		Light float are floating buoys in fixed marine areas to notify ships at sea of the locations of reefs or shallow seas.

Basic requirements

• Shape aids to navigation are designed to indicate locations with shapes or colors during the day.

Types of shape aids to navigation

Types		Descriptions
Unlighted beacon		An unlighted beacon is a boundary mark indicating reefs, shallow-water reefs or uncovered rocks. As it is built underwater separately, the choices location of its installation and design should consider resilience to waves, wind pressure and tidal currents. In particular, clearing marks are to avoid reefs or other dangers.
Buoy		Buoys serves as a guide placed on the sea where fixed marks are not available causing navigation to be difficult. A buoy with a light is called a lighted buoy.
Leading marks		These are designed to indicate sea routes such as channels or harbor entries too narrow for safe passage. They are composed of two landmarks or more in the front and rear of the marine passages or serve as directional signs to guide ship navigation.

Basic requirements

• Sound aids to navigation notify their location to vessels by generating and sending sound waves. Machines that generate sound waves for this purpose are called fog signal emitters.
• Fog signal emitters are built in areas or harbors that often have restricted visibility because of fog, snow, sunset, heavy rain or haze. Under these weather conditions, they are ceaselessly operated during day and night. They have a relatively short aural range. Moreover, the ranges and directions of sound transmission vary depending on weather or sea conditions.

Types of sound aids to navigation

Types		Descriptions
Air siren		A blast of an air siren goes off by means of compressed air. It is attached to a lighthouse in foggy marine areas, by detecting fog and automatically making sounds when fog forms to notify its location to nearby vessels.
Electronic horn		An electronic audio device generates the low-frequency oscillation to ring the tone generator.
Motor Siren		This whistles a blast of siren by motors.

Basic requirements

• The radio navigation or radio-beacon serves as an indicator for ships or aircraft by applying the features of radio waves such as straight-ahead motion, constant velocity or reflex. The benefits of radio waves are that they are available under any weather conditions and used in a broad area.

Types of radio navigation

Types		Descriptions
DGPS station		As an acronym of Differential Global Positioning System, DGPS is an enhancement of the Global Positioning System (GPS) using 21 satellites with auxiliary satellites. It emits G1 D modulated to MSK along with the radio beacon signals (A2, A) in medium frequencies of 283~325kHz by improving localization errors of GPS more accurately. The degree of correction is within 10 meters with the effective range of approximately 100 meters.
Radar Beacon		A racon is a radar transponder that emits non-directional radio waves all day long so that a ship can figure out its location on its radar screen displayed with a Morse bright-line spectrum. It contributes to safe navigation of a ship in a dense fog or bad weather.
LORAN station		LORAN (Long Range Navigation) is a long-range radio navigation system consisting of Loran-A and Loran-C. It is designed to measure the location of a ship by using hyperbolic navigation.