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For this method the AirspaceGeometryComponent class is used to define the aggregation and the Surface class to define the lateral limits of the child airspace (viz. the copies of the lateral limits of the parent airspaces).

The figure below gives illustrates a simple coping of geometry, using as an example of the BRUSSELS TMA which is a Union of two parts: TMA one and TMA two

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There is an additional option here. Insteadd Instead of coping the geometry of the exsisting parts, the parts may be defined as integral part of the geometry of the child airspace. In this case the parent airspace does not exist as own airspace feature.

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This method might be appropriate for data provision between synchronized databases, such as between a local and a regional database and it is equivalent to the approach of the previous AIXM 4.5 version (which is not based on GML). The disadvantage of this method is that the client needs to eventually retrieve the geometry of the referenced Airspace and do the geospatial calculations that are necessary in order to effectively get the actual geometry of the current Airspace in a GML usable form. The advantage is that it preserves a true association with the composing Airspace.

For this method method the AirspaceGeometryComponent class and the AirspaceVolumeDependency class are used to define the aggregation.The Surface class may not be used!

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The AirspaceVolumeDependency.depndency class defines the relationship between the geometry of an AirspaceVolume and the geometry of another (parent) Airspace.

The dependency attribute will be used to define if only the horizontal limits of the "parent" airspace(s) shall be taken into account or also the vertical limits (i.e. the full geometry).

The figure below illustrates a simple referencing, again using as example the BRUSSELS TMA with its two parts: TMA one and TMA two.