Airspace Aggregation -
There are two methods to define the geometry of an airspace with more than one airspace volume:
- by copying the geometry,
- or by referencing.
Combinations of both for defining one airspace geometry are possible.
Copying Geometry
The first method consists in effectively copying the geometry of the referenced Airspace as local AirspaceVolume.
This method might be appropriate for applications that need to provide fully digested geometrical data for direct consumption (e.g. graphical visualization, spatial calculations). The disadvantage of this method is that the referenced geometry might also change in time. This is not a problem when the aggregation is used for the provision of SNAPSHOT data (valid at a time instant), but it might become problematic when providing BASELINE data (which is valid for a period). Future changes of the geometry of referenced airspace needs to be propagated to the AirspaceVolume of the aggregated airspace. The advantage is that this method provides complete geometrical data for the aggregated Airspace and does not require further calculations by the client system.
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 airspace').
The figure below illustrates a simple copying of geometry, using as an example the BRUSSELS TMA, which is a union of two parts: TMA one and TMA two:
The second method is limited to referring to another airspace, but without effectively copying the geometry of that Airspace as own AirspaceVolume.
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 geo-spatial 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, the AirspaceGeometryComponent class and the AirspaceVolumeDependency class are used to define the aggregation.
The AirspaceVolumeDependency 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 considered or also the vertical limits (i.e. the full geometry).
illustrates a simple referencing, again using as example the BRUSSELS TMA with its two parts: TMA one and TMA two.
The coding example below provides a XML fragment of a case like shown above for the fictitious TMA MAGNETTO (example is also part of the AIP Data Set - Specimen (DONLON)).
<aixm:AirspaceTimeSlice gml:id="ASE_MAGNETTO_TMA">
<gml:validTime>
<gml:TimePeriod gml:id="uuid.820fdbbb-55d4-4f45-9d59-d770e5faec95">
<gml:beginPosition>2017-07-01T00:00:00Z</gml:beginPosition>
<gml:endPosition indeterminatePosition="unknown"/>
</gml:TimePeriod>
</gml:validTime>
<aixm:interpretation>BASELINE</aixm:interpretation>
<aixm:sequenceNumber>2</aixm:sequenceNumber>
<aixm:correctionNumber>0</aixm:correctionNumber>
<aixm:featureLifetime>
<gml:TimePeriod gml:id="uuid.5e9c790e-b91b-4182-946d-145b6e0196de">
<gml:beginPosition>2002-11-30T00:00:00Z</gml:beginPosition>
<gml:endPosition indeterminatePosition="unknown"/>
</gml:TimePeriod>
</aixm:featureLifetime>
<aixm:type>TMA</aixm:type>
<aixm:designator>EAMM</aixm:designator>
<aixm:name>MAGNETTO</aixm:name>
<aixm:class>
<aixm:AirspaceLayerClass gml:id="acl123123">
<aixm:classification>C</aixm:classification>
</aixm:AirspaceLayerClass>
</aixm:class>
<aixm:geometryComponent>
<aixm:AirspaceGeometryComponent gml:id="uuid.4344f989-50b4-4cb0-9920-870ccd89429f">
<aixm:operation>BASE</aixm:operation>
<aixm:operationSequence>1</aixm:operationSequence>
<aixm:theAirspaceVolume>
<aixm:AirspaceVolume gml:id="uuid.59160a8e-a015-42ed-8346-34bc65436a72">
<aixm:contributorAirspace>
<aixm:AirspaceVolumeDependency gml:id="uuid.43a4e8ff-7995-492c-aa8f-50ef2c29b679">
<aixm:dependency>FULL_GEOMETRY</aixm:dependency>
<aixm:theAirspace xlink:href="urn:uuid:0df377fe-dd53-4d60-b6c4-6546ef31d26b"/>
</aixm:AirspaceVolumeDependency>
</aixm:contributorAirspace>
</aixm:AirspaceVolume>
</aixm:theAirspaceVolume>
</aixm:AirspaceGeometryComponent>
</aixm:geometryComponent>
<aixm:geometryComponent>
<aixm:AirspaceGeometryComponent gml:id="uuid.e8995bfd-8f47-401e-84d5-81154957ad53">
<aixm:operation>UNION</aixm:operation>
<aixm:operationSequence>2</aixm:operationSequence>
<aixm:theAirspaceVolume>
<aixm:AirspaceVolume gml:id="uuid.a91c0703-1a24-4c0a-a97b-f7a77ae6cdf2">
<aixm:contributorAirspace>
<aixm:AirspaceVolumeDependency gml:id="uuid.28854643-aca8-46e6-a199-57bf0d02a6e2">
<aixm:dependency>FULL_GEOMETRY</aixm:dependency>
<aixm:theAirspace xlink:href="urn:uuid:010d8451-d751-4abb-9c71-f48ad024045b"/>
</aixm:AirspaceVolumeDependency>
</aixm:contributorAirspace>
</aixm:AirspaceVolume>
</aixm:theAirspaceVolume>
</aixm:AirspaceGeometryComponent>
</aixm:geometryComponent>
</aixm:AirspaceTimeSlice>
...
<aixm:AirspaceTimeSlice gml:id="ASE_MAGNETTO1_TMA_P">
<gml:validTime>
<gml:TimePeriod gml:id="uuid.cd76b225-8e1d-4827-b892-e86c68168e9b">
<gml:beginPosition>2017-07-01T00:00:00Z</gml:beginPosition>
<gml:endPosition indeterminatePosition="unknown"/>
</gml:TimePeriod>
</gml:validTime>
<aixm:interpretation>BASELINE</aixm:interpretation>
<aixm:sequenceNumber>2</aixm:sequenceNumber>
<aixm:correctionNumber>0</aixm:correctionNumber>
<aixm:featureLifetime>
<gml:TimePeriod gml:id="uuid.4c1e9902-d3fb-4041-80ff-34e6a9ac0936">
<gml:beginPosition>2010-11-01T00:00:00Z</gml:beginPosition>
<gml:endPosition indeterminatePosition="unknown"/>
</gml:TimePeriod>
</aixm:featureLifetime>
<aixm:type>TMA_P</aixm:type>
<aixm:designator>EAMM1</aixm:designator>
<aixm:name>MAGNETTO TMA PART 1</aixm:name>
<aixm:geometryComponent>
<aixm:AirspaceGeometryComponent gml:id="uuid.dbcb9ad5-2008-4644-becb-4d01dbacc27e">
<aixm:theAirspaceVolume>
<aixm:AirspaceVolume gml:id="uuid.ba335f05-5fff-47f4-81e5-de8df2fa8263">
<aixm:upperLimit uom="FL">460</aixm:upperLimit>
<aixm:upperLimitReference>STD</aixm:upperLimitReference>
<aixm:lowerLimit uom="FL">210</aixm:lowerLimit>
<aixm:lowerLimitReference>STD</aixm:lowerLimitReference>
<aixm:horizontalProjection>
<aixm:Surface xsi:type="aixm:ElevatedSurfaceType" gml:id="uuid.d635cbc1-83ff-490d-8451-7aca0ef6a842">
<gml:patches>
<gml:PolygonPatch>
<gml:exterior>
<gml:Ring>
<gml:curveMember>
<gml:Curve xsi:type="aixm:CurveType" srsName="urn:ogc:def:crs:EPSG::4326" gml:id="uuid.258c16e0-5f2c-4101-aabb-536f58c38eb5">
<gml:segments>
<gml:GeodesicString>
<gml:posList>51.99333333333333 -6.0005
52.45333333333333 -5.869333333333333
52.81666666666667 -5.89 53.53333333333333
-5.981666666666667 53.89333333333333
-5.937833333333333 53.905 -6.0038333333333334
53.916666666666664
-6.099333333333333</gml:posList>
</gml:GeodesicString>
</gml:segments>
</gml:Curve>
</gml:curveMember>
</gml:Ring>
</gml:exterior>
</gml:PolygonPatch>
</gml:patches>
</aixm:Surface>
</aixm:horizontalProjection>
</aixm:AirspaceVolume>
</aixm:theAirspaceVolume>
</aixm:AirspaceGeometryComponent>
</aixm:geometryComponent>
</aixm:AirspaceTimeSlice>
...
<aixm:AirspaceTimeSlice gml:id="ASE_MAGNETTO2_TMA_P">
<gml:validTime>
<gml:TimePeriod gml:id="uuid.ee0a0e78-614e-419e-aebb-57829fd26699">
<gml:beginPosition>2017-07-01T00:00:00Z</gml:beginPosition>
<gml:endPosition indeterminatePosition="unknown"/>
</gml:TimePeriod>
</gml:validTime>
<aixm:interpretation>BASELINE</aixm:interpretation>
<aixm:sequenceNumber>2</aixm:sequenceNumber>
<aixm:correctionNumber>0</aixm:correctionNumber>
<aixm:featureLifetime>
<gml:TimePeriod gml:id="uuid.61902c93-3b1c-4969-90f1-c2422a31f9a2">
<gml:beginPosition>20010-11-01T00:00:00Z</gml:beginPosition>
<gml:endPosition indeterminatePosition="unknown"/>
</gml:TimePeriod>
</aixm:featureLifetime>
<aixm:type>TMA_P</aixm:type>
<aixm:designator>EAMM2</aixm:designator>
<aixm:name>MAGNETTO TMA PART 2</aixm:name>
<aixm:geometryComponent>
<aixm:AirspaceGeometryComponent gml:id="uuid.bbeaa329-9239-4e4f-86e3-95400d7ca76d">
<aixm:theAirspaceVolume>
<aixm:AirspaceVolume gml:id="uuid.fe954643-af04-4334-bd7f-fe969273a9a9">
<aixm:upperLimit uom="FL">460</aixm:upperLimit>
<aixm:upperLimitReference>STD</aixm:upperLimitReference>
<aixm:lowerLimit uom="FL">210</aixm:lowerLimit>
<aixm:lowerLimitReference>STD</aixm:lowerLimitReference>
<aixm:horizontalProjection>
<aixm:Surface xsi:type="aixm:ElevatedSurfaceType" gml:id="uuid.b2444276-e335-4106-9a4a-fd5eeb75b41c">
<gml:patches>
<gml:PolygonPatch>
<gml:exterior>
<gml:Ring>
<gml:curveMember>
<gml:Curve xsi:type="aixm:CurveType" srsName="urn:ogc:def:crs:EPSG::4326" gml:id="uuid.84fe3774-a519-4b16-9344-cb311b2c92b5">
<gml:segments>
<gml:GeodesicString>
<gml:posList>53.876666666666665 -5.863333333333333
53.89333333333333 -5.937833333333333
53.53333333333333 -5.981666666666667
52.81666666666667 -5.89 52.45333333333333
-5.869333333333333 52.516666666666666
-5.850666666666667 52.583333333333336
-5.831666666666667 53.3 -5.755 53.7
-5.786666666666667 53.718333333333334
-5.8083333333333336 53.876666666666665
-5.863333333333333</gml:posList>
</gml:GeodesicString>
</gml:segments>
</gml:Curve>
</gml:curveMember>
</gml:Ring>
</gml:exterior>
</gml:PolygonPatch>
</gml:patches>
</aixm:Surface>
</aixm:horizontalProjection>
</aixm:AirspaceVolume>
</aixm:theAirspaceVolume>
</aixm:AirspaceGeometryComponent>
</aixm:geometryComponent>
</aixm:AirspaceTimeSlice>
More coding examples can be found in the AIP Data Set - Specimen (DONLON).
| No. | Description | XPath Expression |
|---|
ASE-EX-11 ASE-EX-12 ASE-EX-13 | ATS airspace, CTA (Airspace aggregation by copying the geometry), Union of two airspace components | //aixm:AirspaceTimeSlice[@gml:id='ASE_DONLON_CTA'] | /aixm:AirspaceTimeSlice[@gml:id='ASE_DONLON1_CTA_P'] | /aixm:AirspaceTimeSlice[@gml:id='ASE_DONLON2_CTA_P'] |
ASE-EX-14 ASE-EX-15 ASE-EX-16 | ATS airspace, TMA, (Airspace aggregation by referencing), Union of two parts (AirspaceVolumeDependency) | //aixm:AirspaceTimeSlice[@gml:id='ASE_MAGNETTO_TMA'] | //aixm:AirspaceTimeSlice[@gml:id='ASE_MAGNETTO1_TMA_P'] | //aixm:AirspaceTimeSlice[@gml:id='ASE_MAGNETTO2_TMA_P'] |
