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At smaller airports, landing sites or in airspace reserved for specific users (such as gliders) it is possible that a "traffic advisory frequency" is provided. This is used by the pilots flying in the area to announce their flying intentions, for the other pilots to be aware of their position and intended trajectory. In some States this is labelled as "Common traffic advisory frequency". In AIXM, this can be coded using a RadioCommunicationChannel associated with a AirTrafficControlService with type equal-to 'CTAF'. It is not necessary to associate it with a specific Unit, unless there actually exists an ATS Unit that provides some level of air traffic separation service using the same frequency.
Frequency in
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airspace
In AIXM a frequency cannot directly be assigned to an Airspace. The frequency is related to a Service. The Service then is provided within one or more client Airspace. If a Frequency the radio frequency of a Service service is in use for certain FL(s) onlylevels or within a specific geograohical area, this has to can be coded as a Note to the corresponding RadioCommunicationChannel featureusing the RadioFrequencyArea and eventually sector.CircleSector child elements. See also topic ATS Unit providing Service.
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