Navigation and Seamanship

4.3.8. Identification of lights

The navigator must be familiar with the lights and their characteristics printed in the chart to identify each light correctly. Each light is assigned with characteristics of colour and off-on periods for easy identification. In some instances, the shape and colour of the supporting structure will be of assistance in identification.

The vessel will be mislead when the navigator fail to identify lights correctly. The navigator should consult the charts and the Light Lists to learn the exact characteristics of the lights that are expected to appear before his vessel. The colour of the light and flashing characteristics in a full cycle should be carefully noted by the navigator. If colour, cycle, and number of flashes per cycle agree with the information given in the light list or chart, correct identification has been made. Light identification should be done carefully with lights of different intensities, alternate flashing with double colours and at the time of restricted visibility.

It is important to note that in Light Lists all bearings are stated in degrees true, reading clockwise from 000° at north; bearings relating to visibility of lights are given as observed from a a vessel; distances are in nautical miles unless otherwise stated; heights are referred to mean high water; depths are referred to the plane of reference on charts.

A light has distinctive characteristics which distinguish it from other lights or convey specific message. A light may show a distinctive sequence of light and dark intervals. Some navigational lights are fixed, meaning that they burn steadily without on-off characteristics. These characteristic features of a navigational light are the most valuable for identification purposes.

The following are the principal characteristics of lights used for navigational purposes,