Geographic and Nominal Range of Lights

Using the range of a light as a means of judging distance off depends on which of its four ranges you are using (see Figure 12.2). A light's geographical range is the distance it can be seen in conditions of perfect visibility and usually equates to its dipping distance.

Its visual range is the distance it can be made out against its background. This varies with atmospheric conditions and sometimes is increased by using binoculars.

A light's luminous range is the distance it can be seen depending on the current atmospheric conditions.

Its nominal range is the distance at which it can be seen when meteorlogical visibility is 10 nautical miles. This is the range that appears on charts and in lists of lights.

Height of Eye = 10 feet Geographic Range = 11.7nm

Nominal Range = 15nm

I Height of Light = 50 feet

The range at which a light is seen is also affected by visibility. Mist or heat haze can significantly reduce the range at which it can be seen.

12.2 Nominal and Geographic Range of Lights

Height of Eye = 75 feet Geographic Range = 18 nm

The range that you pick up a light depends as much on the height of the light and your height of eye (which together give your geographic range) as its nominal range. On some nights the loom of a light below your horizon can picked up outside your geographic ran

12.2 Nominal and Geographic Range of Lights

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Responses

  • PANDORA
    What is luminious range, geographical range,nominal range?
    3 months ago

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