Also referred to as a Gallery . Port - A Harbor or Port of Call providing protection for vessels. Also the Left side of a vessel, marked by a red light or day-mark. Prism - A transparent piece of glass that refracts or disperses light. Radio Beacon - A fixed radio beacon that aids navigation by sending a radio signal.
Vessels can determine location by taking bearings from several different signals.
When one light is visible directly above the other, you are in the marked channel for safe passage. Reef - A ridge of rocks, sand, or coral at or near the surface of a body of water. Reflect - Bend or throw back light. Refract - Bend or slant rays of light. Revolving Light - A rotating beam of light that produces a flash or characteristic.