Light Characteristic - Abbreviations

Abbreviations

While light characteristics can be described in prose, e.g. "Flashing white every three seconds", lists of lights and navigation chart annotations use abbreviations. The abbreviation notation is slightly different from one light list to another, with dots added or removed, but it usually follows a pattern similar to the following (see the chart to the right for examples).

• An abbreviation of the type of light, e.g. "Fl." for flashing, "F." for fixed.
• The color of the light, e.g. "W" for white, "G" for green, "R" for red. If no color is given, a white light is generally implied.
• The cycle period, e.g. "10s" for ten seconds.
• Additional parameters are sometimes added:

• The height of the light above the chart datum for height (usually based on high water). e.g. 15m for 15 metres.
• The range in which the light is visible, e.g. "10M" for 10 nautical miles.

An example of a complete light characteristic is "Gp Oc(3) W 10s 15m 10M". This indicates that the light is a group occulting light in which a group of three eclipses repeat every 10 seconds; the light is white; the light is 15 metres above the chart datum and is visible for 10 nautical miles (19 km).