Every vessel is required to have certain lights that must be visible. For example, according to "Navigation and Navigational Aids," a vessel is required to have red sidelights on the port (left) side and green sidelights on the starboard (right) side. Also, a white light must be displayed on the stern (back) of the vessel. Other lights are required depending on the size and use of the vessel.
Buoys are markers anchored in the water. Beacons are markers on land and are either lights or daybeacons. Lights are beacons with lights and include lighthouses or simply a pole with a light. Daybeacons are beacons without lights. According to "Aids to Navigation," the Coast Guard follows the system of the International Association of Lighthouse Authorities (IALA). As a vessel travels upstream, buoys and beacons on the port side will be marked in green and with odd numbers that increase as the vessel continues upstream. The buoys and beacons on the starboard side will be red and marked with even numbers that will also increase as the vessel moves upstream. Other buoys signify danger, do not enter or speed restrictions.
Boats are required by law to have a sound signal. These are used in times of poor visibility or when entering a channel or coming around a bend. Sound signals are also used when passing or overtaking another vessel. Fog horns are also a part of the ATON system and are usually found with beacons and buoys. These are used in conjunction with other navigational aids to assist vessels in times of poor visibility.
There are several electronic devices that assist boaters with navigation. One of these is LORAN-C. According to "Navigation and Navigational Aids," LORAN-C is the most popular radio navigation system in the United States. LORAN, or long range navigation, receives signals from radio transmissions from shore to determine the location of the vessel. Other devices include global positioning system (GPS) and satellite systems. For emergencies, Emergency Position Indicating Radio Beacon (EPIRB) is available and will transmit a distress signal along with the location of the vessel.
There is other equipment available to assist with navigation. One of these is a radar. This system sends radio waves through the air. When the waves hit something, the waves are reflected back. The time that this takes allows the system to calculate the distance to the other object. Another similar piece of equipment is the depth finder. This functions in a similar way to the radar system by sending out ultrasound waves through the water to determine the depth of the water.
