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There is an additional option here. 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 instance of the airspace feature.
Referencing
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The figure below illustrates a simple referencing, again using as example the BRUSSELS TMA with its two parts: TMA one and TMA two.
Coding Examples
Example 1-1: R-4912 Sand Springs, NV
This example shows the encoding of the geometry of a Restricted area (R-4912) utilizing the AIXM airspace aggregation concept.
The airspace aggregation is made of 4 airspace components which are used in a combination of referencing and copying and referencing.
The first AirspaceGeometryComponent used in this aggregation is the 'BASE' from which 3 other airspace geometry components are substracted.
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The 'BASE' is defined with theAirspaceVolume defining an upperLimit, a lowerlimit and a Surface that has the shape of rectangular (in the figure below highligted in orange, "BASE1").
The second AirspaceGeometryComponent is used for a 'SUBSTRSUBTR' operation applied on the 'BASE' component ("SUBTR2").
For this substraction subtract operation the referencing concept is applied, i.e the AirspaceVolumeDependency class has to be defined. According to this concept the contributorAirspace ("Airspace3") may not have its own defined Surface that is part of the Airspace definition of 'R4912', but is just referenced using theAirspace property. Airspace3 is actually the airsapce 'R-4804A Twin Peaks, NV' which has its own defined geometry components.
The dependency is coded as 'HORZ_PROJECTION'. That means that the substraction is limited to the horizontal projection.
The whereas only teh horizonal projection is tajken into account. The which Hence, the vertical limits of 'R-4804A are not taken in into account.The AirspaceGeometryComponent "SUBTR2" has its own defined upperLimit and lowerLimit which equals the vertical limits defined for "BASE1".
This subtract operation of "SUBTR2" results in a corresponding shape (in the figure below highligted in orange).
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| Only the horizontal projection is taken into account, not the full geometry. The full geometry would also take the vertical component into account. |
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Example: Twin Peaks
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Image RemovedThe third AirspaceGeometryComponent is again a 'SUBTR' operation applied on the 'BASE' component ("SUBTR3").
Again, the referencing method is applied utilising the AirspaceVolumeDependency class and its properties defining a horizontal projection dependency only.
After the subtract operation of "SUBTR3" the resulting shape is as highligted in orange in the figure below.
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Again the vertical limits of the referenced airspace ("Airspace2"), i.e. 'R-4810 DESERT MOUNTAINS, NV', are not taken into account, but the ones defined for airspace component "SUBTR3".
Note that the upper limit of 'R-4810' is lower than the one of airspace component "SUBTR3".
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Finally, the fourt AirspaceGeometryComponent is again a 'SUBTR' operation applied on the 'BASE' component ("SUBTR4").
But in this case the referncing method i.e. AirspaceVolumeDependency class is not used.
The vertical limits and the Surface of "SUBTR4" is defined as integral part within the Airspace definition of 'R4912'. (This may be the copy of another airspace.)
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Example 1-2: R-4804A Twin Peaks, NV
The airspace used in the privous example in the "SUBTR2" operation, 'R-4804A Twin Peaks, NV', itself ia made of an airspace aggregation.
Note if the horizontalProjection of of 'R-4804A Twin Peaks, NV' is changed also the horizontal shape of 'R-4912 Sand Springs, NV' is affected.
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R-4804A Twin Peaks, NV' is made of three airspace geometry components, a BASE, a UNION and a SUBTR.
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The BASE is defined with verticla limits and a surface that has a shape of a circle by centre point.
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The UNION component is also defined by its own vertical limits and surface, that has a shape of a circle by centre point.
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Also the SUBTR component is defined by its own vertical limits and surfcae.
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More examples TBD in the scope of the DONLON AIXM XML AIP data set.