AerodromeHorizontalVisibility


             AerodromeHorizontalVisibility

An aggregation of horizontal visibility conditions typically reported together at an aerodrome, including the prevailing visibility and minimum visibility. Direction of minimum visibility shall be given in degrees from true North. Plane angle unit of measure (uom) is deg". Measured prevailing and minimum horizontal visibility, if present, shall be reported in meters ("m") only."

Properties	Definition	Type
minimumVisibility	The minimum observed visibility. Measured minimum visibility shall be reported in meters (m") only. ICAO Annex 3 / WMO No. 49-2 Section 4.2.4.4a: "When the visibility is not the same in different directions and a) when the lowest visibility is different from the prevailing visibility, and 1) less than 1500 m or 2) less than 50 percent of the prevailing visibility and less than 5000 m; the lowest visibility observed should also be reported and,when possible, its general direction in relation to the aerodrome reference point indicated by reference to one of the eight points of the compass. If the lowest visibility is observed in more than one direction, then the most operationally significant direction should be reported; and b) when the visibility is fluctuating rapidly, and the prevailing visibility cannot be determined, only the lowest visibility should be reported, with no indication of direction	DistanceWithNilReason
minimumVisibilityDirection	The direction of the minimum visibility relative to the reporting station. This is optional in cases where minimum visibility is reported but the visibility is fluctuating rapidly. Minimum visibility is reported in cardinal and inter-cardinal directions (N, NE, E, SE, S, SW, W, and NW) Direction of minimum visibility shall be given in degrees from true North. Plane angle unit of measure (uom) is deg"."	AngleWithNilReason
prevailingVisibility	The reported prevailing horizontal visibility at the surface that is representative of the aerodrome. Measured prevailing horizontal visibility shall be reported in meters (m") only. The greatest visibility value, observed in accordance with the definition of "visibility", which is reached within at least half the horizon circle or within at least half of the surface of the aerodrome. These areas could comprise contiguous or non-contiguous sectors. Note: This value may be assessed by human observation and/or instrumented systems. When instruments are installed, they are used to obtain the best estimate of the prevailing visibility. To report a prevailing visibility of at least 10000 meters, prevailing visibility is reported as 10000 meters and the prevailing visibility operator is reported as "above". ICAO Annex 3 / WMO No. 49-2: Section 4.2.4.4b"	DistanceWithNilReason
prevailingVisibilityOperator	The reported relational operator for the prevailing horizontal visibility. When reported, this operator is reported in conjunction with prevailing visibility. To report a prevailing visibility of at least 10000 meters, prevailing visibility is reported as 10000 meters and the operator is reported as above". When no operator is reported, prevailing visibility represents an exact value with identical semantics to other measured quantities"	RelationalOperator

Details

AerodromeHorizontalVisibility


              AerodromeHorizontalVisibility

Semantic Correspondence

AIRM Concept	Definition
HorizontalVisibility	An aggregation of horizontal visibility conditions typically reported together at an aerodrome, including the prevailing visibility and minimum visibility.

minimumVisibility


              AerodromeHorizontalVisibility.minimumVisibility

The minimum observed visibility. Measured minimum visibility shall be reported in meters (m") only. ICAO Annex 3 / WMO No. 49-2 Section 4.2.4.4a: "When the visibility is not the same in different directions and a) when the lowest visibility is different from the prevailing visibility, and 1) less than 1500 m or 2) less than 50 percent of the prevailing visibility and less than 5000 m; the lowest visibility observed should also be reported and,when possible, its general direction in relation to the aerodrome reference point indicated by reference to one of the eight points of the compass. If the lowest visibility is observed in more than one direction, then the most operationally significant direction should be reported; and b) when the visibility is fluctuating rapidly, and the prevailing visibility cannot be determined, only the lowest visibility should be reported, with no indication of direction

Semantic Correspondence

AIRM Concept	Definition
HorizontalVisibility.minimumVisibility	Visibility for aeronautical purposes is the greater of: a) the greatest distance at which a black object of suitable dimensions, situated near the ground, can be seen and recognized when observed against a bright background; b) the greatest distance at which lights in the vicinity of 1 000 candelas can be seen and identified against an unlit background.

minimumVisibilityDirection


              AerodromeHorizontalVisibility.minimumVisibilityDirection

The direction of the minimum visibility relative to the reporting station. This is optional in cases where minimum visibility is reported but the visibility is fluctuating rapidly. Minimum visibility is reported in cardinal and inter-cardinal directions (N, NE, E, SE, S, SW, W, and NW) Direction of minimum visibility shall be given in degrees from true North. Plane angle unit of measure (uom) is deg"."

Semantic Correspondence

AIRM Concept	Definition
HorizontalVisibility.minimumVisibilityDirection	The direction of the minimum visibility relative to the reporting station.

prevailingVisibility


              AerodromeHorizontalVisibility.prevailingVisibility

The reported prevailing horizontal visibility at the surface that is representative of the aerodrome. Measured prevailing horizontal visibility shall be reported in meters (m") only. The greatest visibility value, observed in accordance with the definition of "visibility", which is reached within at least half the horizon circle or within at least half of the surface of the aerodrome. These areas could comprise contiguous or non-contiguous sectors. Note: This value may be assessed by human observation and/or instrumented systems. When instruments are installed, they are used to obtain the best estimate of the prevailing visibility. To report a prevailing visibility of at least 10000 meters, prevailing visibility is reported as 10000 meters and the prevailing visibility operator is reported as "above". ICAO Annex 3 / WMO No. 49-2: Section 4.2.4.4b"

Semantic Correspondence

AIRM Concept	Definition
HorizontalVisibility.prevailingVisibility	The greatest visibility value, observed in accordance with the definition of visibility", which is reached within at least half the horizon circle or within at least half of the surface of the aerodrome. These areas could comprise contiguous or non-contiguous sectors."

prevailingVisibilityOperator


              AerodromeHorizontalVisibility.prevailingVisibilityOperator

The reported relational operator for the prevailing horizontal visibility. When reported, this operator is reported in conjunction with prevailing visibility. To report a prevailing visibility of at least 10000 meters, prevailing visibility is reported as 10000 meters and the operator is reported as above". When no operator is reported, prevailing visibility represents an exact value with identical semantics to other measured quantities"

Semantic Correspondence

AIRM Concept	Definition
RunwayVisualRange.rvrValueInterpretation	The relational operator that can be used for interpreting the RVR value, for instance in order to express a mean RVR of at least 2000 meters (ABOVE 2000 meters).