Visual aids to navigation: Marking their location with lights at night
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 of visual aids to navigation
| Types |
Descriptions |
| Lighthouse |
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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 |
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The purpose of a light pole is the same as that of a lighthouse, but it has simple column structure with floating lights. |
| Lighted beacon |
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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. If it has lighting, it is called a lighted beacon; if not, it is known as an unlighted beacon. |
| Illuminated light |
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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 |
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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. |
| Direction light |
 |
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. |
| Lighted buoy |
 |
Lighted buoys are floating buoys in fixed marine areas to notify ships at sea of the locations of reefs or shallow seas. If it has lighting, it is called a lighted buoy, if not, it is known as an unlighted buoy. |
Shape aids to navigation: Marking locations with shapes or colors during daytime
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 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 |
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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. |
Sound aids to navigation: Marking locations with sounds when visibility is limited by fog, snow, rain, etc.
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 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 |
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An electronic audio device generates the low-frequency oscillation to ring the tone generator. |
| Motor Siren |
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This whistles a blast of siren by motors. |
Radio navigation: Applying a variety of properties of radio frequencies
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 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 |
 |
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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. |
Special purpose aids to navigation: notifying day and night ships at sea of various navigation related information such as vessel traffic at narrow straits or waterways, tidal currents in the form of radio waves or shapes, or other navigational data.
- Vessel traffic service (VTS) is designed to guide ships at sea for safe navigation by installing radar and CCTVs in waters where a ship enters or departs, or accesses a port, or in narrow channels.
- Tidal current signal station: Designed to notify the strengths and directions of tidal currents to ships sailing in waters under high tidal influence such as harbor entrances or channels, or narrow channels by using a jumbotron screen signal system.
- Weather signal box: Designed to notify necessary data such as special weather reports to ships at sea.
- Aids to navigation& the Automatic Identification System (AtoN AIS) are designed to mark the locations and status of aids to navigations on the electronic navigation chart and also provide all sorts of safety related information.
