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A navaid equipment may have different types of limitations. The code list of the RadioFrequencyArea.type attribute provides the following values to define the type of the navaid limitation.
| CodeRadioFrequencyAreaType | Definition |
|---|---|
| '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 |
| Warning | ||
|---|---|---|
| ||
The definitions of COV and T-COV are wrong. Hence, avoid coding this values. There is no clear ICAO definition of the "actual coverage" term, while the "Operational Service Volume" seems to have a precise FAA definition. Therefore, this assumption that COV and OSV mean the same risks being incorrect. T_COV: This definition also makes an assumption for which there is no clear basis in ICAO or in other specifications. Workaround AIXM 5.1(.1): use OTHER, e.g. OTHER:SV (for service volume) - for DME, aligned with ED-77 OTHER:SSV (for standard service volume) OTHER:DOC (for designated operational coverage) OTHER:COV (when the data provider indicates simply 'coverage' without further details. etc. Status AIXM 5.2: see CCB AIXM-376 |
Navaid service areas are modelled as volumes of airspace described as circle sectors, centred on the NavaidEquipment in which certain limitations in the navaid performance are defined. The CircleSector class is defined by describing a start angle, stop angle, inner distance, outer distance and upper/lower altitude. Each instance of the limitation associated with a Navaid describes a single sector and with a single type of limitation. A service area may consist of more than one circle sector.
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