[AIXM-560] Radio frequency coverage and limitations clarification

Description

Update of the CodeRadioFrequencyAreaBaseType list of values.

Rationale for change

See https://aixmccb.atlassian.net/browse/AIXM-376

The CodeRadioFrequencyAreaBaseType provides the list of values that can be used for coding the coverage and related signal limitations for a navaid equipment, service frequency, surveillance equipment, etc. It currently comprises the following values:

• COV = Actual coverage range (flight checked). Equivalent to Operational Service Volume.
• T_COV = Theoretical coverage range (not flight checked). Equivalent to Standard Service Volume.
• SCL = Scalloping.
• RHG = Roughness (signal roughness experienced).
• UNREL = Unreliability.
• RES = Restricted (use is restricted to defined sectors).
• UUS = Un-usability (use is not permitted in the defined sectors).
• OUT = Out of tolerance.
• ESV = Extended Service Volume (Coverage)
• OTHER = Other.

Some of the values in this list do not have a clear meaning and some values used in practice are missing from this list, as follows:

1) The value COV definition refers to "actual coverage range (flight checked)” and it indicates that this is equivalent to the “Operational Service Volume (OSV)." The term OSV appears in ARINC 424, as a characteristic of the DME signal.  No definition of the "actual coverage" term could be found in the ICAO documents. The term “coverage” is used extensively in the ICAO Annex 10, but without a clear definition. For example:

• “The localizer shall provide signals sufficient to allow satisfactory operation of a typical aircraft installation within the localizer and glide path coverage sectors”;
• “The coverage area is that area within which the SBAS broadcast can be received (i.e. the geostationary satellite footprints).”

In ARINC 424, the term coverage is defined as part of the Navaid Limitations Code filed to indicate “maximum reception reliability”.

In the FAA TERPS standard, the term “service volume” is used and defined as “volume of airspace surrounding a VOR, TACAN, or VORTAC facility within which a signal of usable strength exists and where that signal is not operationally limited by cochannel interference”.

In State AIS publications, “coverage” is used as a generic term to indicate an airspace volume within which the signal may be received.

Proposal: keep COV, but defined as “The volume of airspace within which the radio signal is reliably received to the level specified by the applicable standards”.

2) T_COV="Theoretical coverage range (not flight checked). Equivalent to Standard Service Volume." The term “theoretical coverage” is not defined by ICAO. FAA defined Standard Service Volume (SSV) as “SSV defines the reception limits of unrestricted NAVAID's which are usable for random/unpublished route navigation”

Proposal: delete T_COV. Add SSV (Standard Service Volume).

3) Clarify the definition of Extended Service Volume (ESV), using the FAA definition “reception limits which are usable for unpublished route navigation and which are flight checked to confirm these limits of coverage”

4) Many States, in particular in Europe, publish a “designated operational coverage (DOC)”, which is defined as “the airspace where the frequency assignment planning process provides protection from other assignments” and required to be published in AIP by the EUR DOC 7754 - EUR ANP, VOLUME II, FASID. Proposal: add the value DOC to the current list of values.

5) Approach Service Volume (ASV) is missing from the current list. It is used to designate sectors of circle aligned with the final approach paths, where the signal satisfies the applicable standards.

Impact assessment

[FWD_MAP_1:1] Data mapping is possible and no data loss occurs when data is exchanged from a system (A) that uses AIXM 5.1.1 for output towards a system (B) that uses AIXM 5.2 for input.

[BWD_MAP_1:1] Data mapping is possible and no data loss occurs when data is exchanged from a system (B) that uses AIXM 5.2 for output towards a system (A) that uses AIXM 5.1.1 for input.

Change Proposal details

In the UML model, update the list of values of the CodeRadioFrequencyAreaBaseType <<codelist>> as follows:

• Change the definition of the value COV to read: “The volume of airspace within which the radio signal is reliably received to the level specified by the applicable standards”;
• Add the value DOC defined as “Designated Operational Coverage. the airspace where the frequency assignment planning process provides protection from other assignments (source EUR DOC 7754 - EUR ANP, VOLUME II, FASID)”;
• Change the definition of the value ESV to read: “Extended Service Volume. Reception limits which are usable for unpublished route navigation and which are flight checked to confirm these limits of coverage (source: FAA Flight Inspection Handbook)”;
• Add the value SSV defined as “Standard Service Volume. Defines the reception limits of unrestricted navaid which are usable for random/unpublished route navigation”
• Add the value ASV defined as “Approach Service Volume. Designates sectors of circle aligned with the final approach paths, where the signal satisfies the applicable standards”;
• Delete the value

The following UML class diagram indicates the modified codelist values:

Mapping AIXM 5.1.1 to AIXM 5.2 (forward)

The following algorithm shall be applied:

• [MAPC-01] For each RadioFrequencyArea that has a type child element, convert its value as follows (if applicable):
  • Replace OTHER:DOC with DOC
  • Replace OTHER:SSV with SSV
  • Replace OTHER:ASV with ASV
  • Replace T_COV with OTHER:T_COV

Mapping AIXM 5.2 to AIXM 5.1.1 (backward)

The following algorithm shall be applied:

• [MAPC-01] For each RadioFrequencyArea that has a type child element, convert its value as follows (if applicable):
  • Replace DOC with OTHER:DOC
  • Replace SSV with OTHER:SSV
  • Replace ASV with OTHER:ASV

Mapping example

(Note: for mapping test data see: https://github.com/aixm/mapping_52_511/tree/master/AIXM-xxx) 

AIXM Input	AIXM Output