Meteorological Visibility - Revision history

Minsuids: Dictionary clean-up: identifier → urn:mrn:iala:dic:2-1-0280

2026-09-17T09:17:47Z

Dictionary clean-up: identifier → urn:mrn:iala:dic:2-1-0280

← Older revision		Revision as of 09:17, 17 September 2026
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	'''2-1-~~280~~		'''urn:mrn:iala:dic:2-1-0280'''

	The greatest distance at which a black object of suitable dimensions can be seen and recognised by day against the horizon sky, or, in the case of night observations, could be seen and recognised if the general illumination were raised to the normal daylight level. The term may express the visibility in a single direction or the prevailing visibility in all directions.		The greatest distance at which a black object of suitable dimensions can be seen and recognised by day against the horizon sky, or, in the case of night observations, could be seen and recognised if the general illumination were raised to the normal daylight level. The term may express the visibility in a single direction or the prevailing visibility in all directions.

Minsuids: Dictionary clean-up (editorial, no change of meaning): stray labels inside sentences removed

2026-09-17T06:44:34Z

Dictionary clean-up (editorial, no change of meaning): stray labels inside sentences removed

← Older revision		Revision as of 06:44, 17 September 2026
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	Reference: W.M.O. (modified)		Reference: W.M.O. (modified)

	Symbol: V ~~Unit: kilometre (km); sea-mile (s.m.)~~		Symbol: V

			Unit: kilometre (km); sea-mile (s.m.)

	Note 1: It has been established that in such circumstances an object may be seen and recognised if a certain value of the contrast threshold C is reached (2-1-295 and 2-1-300). For practical observations, the value of C = 0.05 has been agreed by the Reference: W.M.O. In the case of a uniform atmosphere, the visibility so defined is equal to, where s is the atmospheric extinction coefficient (2-1-270, Note 2:).

	In ~~Germany~~, the visibility so defined ~~has the Symbol: V0.05 and~~ is ~~often called~~ the ~~Praktische Sichtweite~~.		Note 1: It has been established that in such circumstances an object may be seen and recognised if a certain value of the contrast threshold C is reached (2-1-295 and 2-1-300). For practical observations, the value of C = 0.05 has been agreed by the W.M.O. In the case of a uniform atmosphere, the visibility so defined is equal to, where s is the atmospheric extinction coefficient (2-1-270, Note 2).

			In Germany, the visibility so defined has the symbol V0.05 and is often called the Praktische Sichtweite.

	Note 2: Under ideal conditions (in daylight laboratory observation), however, C is equal to 0.02. A visibility defined by this value has been called the Meteorological Range (and, in German, Normsichtweite, with Symbol: VN)

	In the case of a uniform atmosphere, the visibility so defined is equal to , where s is the atmospheric extinction coefficient (2-1-270, Note 2:).		Note 2: Under ideal conditions (in daylight laboratory observation), however, C is equal to 0.02. A visibility defined by this value has been called the Meteorological Range (and, in German, Normsichtweite, with symbol VN)

			In the case of a uniform atmosphere, the visibility so defined is equal to , where s is the atmospheric extinction coefficient (2-1-270, Note 2).

	{{IALAFooter}}		{{IALAFooter}}

Minsuids at 11:55, 3 February 2024

2024-02-03T11:55:56Z

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	[[Category:Alphabetical Index]]		[[Category:Alphabetical Index]]
	[[Category:IALA Dictionary 1970-89 Edition]]		[[Category:IALA Dictionary 1970-89 Edition]]
			[[Category:IALA Dictionary 2023 Revision]]

Oferiks: 1 revision

2009-03-01T10:00:48Z

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2009-02-25T10:00:08Z

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Oferiks: 1 revision

2009-02-25T00:00:08Z

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Oferiks at 12:00, 15 February 2009

2009-02-15T12:00:00Z

New page

'''2-1-280

The greatest distance at which a black object of suitable dimensions can be seen and recognised by day against the horizon sky, or, in the case of night observations, could be seen and recognised if the general illumination were raised to the normal daylight level. The term may express the visibility in a single direction or the prevailing visibility in all directions.

Reference: W.M.O. (modified)

Symbol: V Unit: kilometre (km); sea-mile (s.m.)

Note 1: It has been established that in such circumstances an object may be seen and recognised if a certain value of the contrast threshold C is reached (2-1-295 and 2-1-300). For practical observations, the value of C = 0.05 has been agreed by the Reference: W.M.O. In the case of a uniform atmosphere, the visibility so defined is equal to, where s is the atmospheric extinction coefficient (2-1-270, Note 2:).

In Germany, the visibility so defined has the Symbol: V0.05 and is often called the Praktische Sichtweite.

Note 2: Under ideal conditions (in daylight laboratory observation), however, C is equal to 0.02. A visibility defined by this value has been called the Meteorological Range (and, in German, Normsichtweite, with Symbol: VN)

In the case of a uniform atmosphere, the visibility so defined is equal to , where s is the atmospheric extinction coefficient (2-1-270, Note 2:).

{{IALAFooter}}

{{languages|Meteorological Visibility}}
[[Category:2.1 Optics and Vision]]
[[Category:Alphabetical Index]]
[[Category:IALA Dictionary 1970-89 Edition]]