AvXML Packages

AvXML is built on several packages. There is not yet a formal agreement between WMO and ICAO on how the packages will be managed. For convenience, in AvXML 1.0 the packages are divided into a group that is concerned with the meteorological information content (this group is labelled as 'managed by WMO'), and a group that is concerned with how the meteorological information is applied within the aviation community (this group is labelled as 'packages managed by ICAO').

Packages managed by WMO

• metce - a set of foundation building blocks to support application schema in the domains of interest to WMO, notably the weather, climate, hydrology, oceanography and space weather disciplines
• Observable Property Model - based on work by the OGC Sensor Working Group, this allows creation of definitions that are derived from the meteorological basic types.

Packages managed by ICAO

• iwxxm - ICAO Meteorological Information Exchange Model - defines the reports required by ICAO (the equivalent of METAR/SPECI, TAF and SIGMET) that are built from the components of the packages managed by WMO
• saf - Simple Aeronautical Features, that allow items such as airports, or runways to be described to the level of detail required for reporting aviation weather

More on the packages managed by WMO (metce, Meteorological Basic Types and Observable Property Model

metce

metce provides a set of foundation building blocks that can be built into an application schema; iwxxm is the first example.

The WMO Logical Data Model (known as metce) is implemented in two parts:

• metce (the WMO Logical Data Model itself)
• Observable Property Model (this may be replaced by a package being developed by OGC when the latter is finalised)

Observable Property Model

The 'Observable Property Model' provides a framework for qualifying or constraining physical properties. For example, the model enables a standard physical property such as "air temperature" to be qualified as "daily maximum air temperature" by specifying an aggregation period of 24-hours using the "maximum" statistical function.

This model is derived from work undertaken in the OGC Sensor Web Enablement SWG.

As an interim measure, the WMO Logical Model includes the Observable Property Model. Further discussions on the governance arrangements of this model are pending.

metce (Modèle pour l'Échange des informations sur le Temps, le Climat et l'Eau)

The WMO Logical Data Model is intended to support the entire scope of WMO concerns: weather, climate and water. To reflect this scope, the WMO Logical Data Model is named 'Modèle pour l'Échange des informations sur le Temps, le Climat et l'Eau' (METCE). In English, it may also be known as the ‘METeorological Community Exchange’ model.

WMO METCE is intended to provide conceptual definitions of meteorological phenomena, entities and concepts in order to underpin semantic interoperability in the weather, climate and water domain.

The «Application Schema» includes:

• specialisations of OM_Observation, OM_ComplexObservation and OM_DiscreteCoverageObservation classes (from ISO 19156)
• a concrete implementation of OM_Process (from ISO 19156)
• a number of meteorological feature types and categorisation schemes thereof.

The 'WMO METCE' «Application Schema» will typically be imported to provide a baseline conceptual model framework upon which community-specific Application Schema are based.

More on the packages managed by ICAO (iwxxm, saf)

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iwxxm (ICAO Weather Information Exchange Model)

The ICAO Weather Information Exchange Model (IWXXM) package, including METAR, SPECI, TAF, and SIGMET reports as defined in ICAO Annex 3, 17th edition. These four reports are essential operational meteorology products used to enable safe and efficient air travel worldwide.

Structure of iwxxm package

This package builds upon the ISO 19100 family (ISO TC211) and WMO standard meteorological modeling constructs. Additionally, the constructs in this application schema refer to a number of aviation constructs such as FIR, Aerodrome, and Runway from the Simple Aviation Features package. The full relationship of this package with external dependencies are shown in the 'Package Dependencies' diagram.

While only four of the reports from Annex 3 are currently represented, this may be expanded in a future version.

Reports in the package - METAR/SPECI

Observation of meteorological conditions made at an aerodrome throughout the day. METARs may also include short-term forecasts of meteorological conditions

Reports in the package - TAF

Routine aerodrome forecasts of meteorological conditions

Reports in the package - SIGMET

Meteorological advisory concerning the occurrence and/or expected occurrence of weather phenomena which may affect the safety of aircraft operations, such as severe thunderstorms or turbulence

saf (Simple Aviation Features) package

Simplified features from the aviation domain, such as aerodrome and runway. These features are not intended for storage or transmission, merely simplified variants of aviation concepts that can be referenced from other packages.