Magnetic Variation

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 (Aeronautical Data Catalogue) requires the magnetic variation only for ILS and NDB.

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

For some Navaids (viz. VOR, ILS and MLS), PANS-AIM requires a station declination instead of a local magnetic variation (see corresponding specialised navaid equipment topic for details).

Coding Examples

Coding examples can also be found in the AIP Data Set - Specimen (DONLON):

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']