Introduction
For ATS airspace, PANS-AIM requires the class of airspace as part of the minimum AIP data set.
In AIXM 5, the class of airspace is encoded by the using the AirspaceLayerClass.classification attribute. The codeAirspaceClassificationType contains a list of value for all classes ('A'-'G'). The value 'OTHER' should not be used.
In AIXM it is possible to encode one class for the whole airspace but also different classes for several layers within an airspace. For the latter, the AirspaceLayer class is used in association with the AirspaceClassLayer. For coding of the vertical limits see Vertical Limits of Airspace.
For certain ATS airspace, such as TMA and CTR, it is possible the airspace classification changes in time. For example, it is possible that the airspace class E is extended to a higher level during weekends. This is supported through the timesheets associated with the AirspaceLayerClass, which is a specialisation of the PropertiesWithSchedules class (see the general coding guidelines for schedules).
The altitudeInterpretation attribute might be also useful, as it allows to indicate that the upper or lower limit of the airspace layer is excluded in a certain class. For example, certain AIS publications indicate explicitly that the airspace is "class D up to and including FL 065". The current list of values allows only exclusions ('ABOVE_LOWER', 'BELOW_UPPER') to be coded explicitly.
AIXM 5.1(.1) issue
In the current AIXM 5.1(.1) version, some values do not match their description. For example, "ABOVE_LOWER" is actually defined as "at or above the lower altitude". In order to avoid confusions, it is possible to code explicitly an additional "AT" value if necessary to indicate that a certain airspace class is applicable at the upper or lower limit.
AIXM 5.2 Change
A Change Proposal approved by the AIXM CCB for the next version will clarify the coded values of the altitudeInterpretation. See [AIXM-480] Clarify the meaning of SegmentLeg vertical limits and the values of the CodeAltitudeUseType.
Coding Examples
The figure below shows a simple coding example of the class of the AMSWELL FIR including different airspace layers.
More examples can be found in the AIP Data Set - Specimen (DONLON).
| No. | Description | XPath Expression |
|---|---|---|
| ASE-EX-01 | ATS airspace, FIR | //aixm:AirspaceTimeSlice[@gml:id='ASE_AMSWELL_FIR'] |
| ASE-EX-02 | ATS airspace, TMA | //aixm:AirspaceTimeSlice[@gml:id='ASE_DONLON_TMA'] |