PANS-AIM requires the magnetic variation for all radio navigation aids without limitation to a particular type of navaid (see chapter 5.3.3.1 and ENR 4.1). However, PANS-AIM Appendix 1 requires the magnetic variation only for ILS and NDB.
PANS-AIM issue
PANS-AIM ENR 4.1 requires a magnetic variation independently from the type (except VOR and ILS for which a Station declination is required). PANS-AIM appendix 1 requires a magnetic variation only for ILS and NDB. For the ILS it also requires a station declination. Is this correct, i.e. is mag var and st. decl. needed for an ILS?
In AIXM 5, the magnetic variation is coded on the specialised classes of the abstract NavaidEquipment class (see also topic Navaid Equipment).
Several attributes are used.
The magneticVariation attribute is used to provide the angular value of the magnetic variation. The value of an angle (at a given point) between the direction of Magnetic North and the direction of Geographical North. The value range allowed by AIXM is between -180 and 180 degrees. A positive value indicates that Magnetic North is East of Geographical North. A negative value indicates that Magnetic North is West of Geographical North.
The dateMagneticVariation is the year on which an associated magnetic variation was measured.
In addition, PANS-AIM requires, for ILS Localiser and NDB, the accuracy to be provided. For both a accuracy of 1 degree is required. In AIXM, the magneticVariationAccuracy attribute is used to code that information.
Note
Coding Rules for Magnetic Variation for Navaid
| Identifier | Data Encoding Rule | Justification | Data Verification Rule (UID) | Remarks |
|---|---|---|---|---|
| NAV-301 | For VOR or TACAN having a specified magneticVariation and dateMagnteicVariation, these values have to coincide with those of the AirportHeliport related to the Navaid the VOR or TACAN is a NavaidEquipment of. | EAD | TBD | |
| NAV-302 | If magneticVariation is specified, then dateMagnteicVariation is mandatory. | EAD / Data consistency | TBD | |
| NAV-303 | If magneticVariation is specified, then magneticVariationAccuracy should be provided. | PANS-AIM | TBD |
Coding Examples
See topic Navaid [NAV]..
Coding examples can also be found in the DONLON AIP data set file:
| No. | Description | XPath Expression |
|---|---|---|
NDB-EX-01 | NDB (with magnetic variation coded) | //aixm:NDBTimeSlice [@gml:id ='NDB_DON'] |
NDB-EX-02 | NDB (with magnetic variation unknown) | //aixm:NDBTimeSlice [@gml:id ='NDB_KL'] |