Sector light Authorities). For example, the United States uses a signalling stereotype which is the opposite of Europe. In USA, the red light indicates the starboard side of the channel for harbour bound vessels, while the green light indicates the port side of the same channel. An expression to remind of this is "red right returning". An example of a sector light is the light of the Fisgard Lighthouse in British Columbia. The lighthouse as built to guide ships through the entrance of Esquimalt harbour. The white sector is an isophase light of 2s from 322° to 195°. If the ship sees
Ship motions or "roll axis", is an imaginary line running horizontally through the length of the ship, through its centre of gravity, and parallel to the "waterline". A roll motion is a side-to-side or port-starboard tilting motion of the superstructure around this axis. There are three special axes in any ship, called vertical, transverse and longitudinal axes. The movements around them are known as roll, pitch and yaw. There are methods for both passive and active motion stabilization used in some designs. They include static hull features such as skegs and bilge keels, or active mechanical devices like counterweights, antiroll tanks and