Navaid [NAV]

The figure below shows the main AIXM 5 classes used for the navaid concept.

In AIXM 5, a Navaid is composed of one or more NavaidEquipment.

To describe a physical navaid equipment in AIXM 5, the NavaidEquipment class is used. This class is specialised into: Azimuth, DME, DirectionFinder, Elevation, Glidepath, Localizer, MarkerBeacon, NDB, SDF, TACAN, VOR.

Some examples:

A Navaid may be a NDB which will be composed of just one NavaidEquipment, viz. a NDB.

A Navaid may be a VOR/DME which will be composed of two NavaidEquipment, viz. a VOR and a DME.

A Navaid may be an ILS which will be composed of several NavaidEquipment, e.g. a Localizer, a Glidepath and one or more MarkerBeacon or a DME.

The relationship between the NavaidEquipment may be further described by using the NavaidComponent class.

The Navaid class carries the attributes that are common for the composition of the whole navaid. These are some basic data such as the type of the navaid, its designator and name.

In addition, also related to Navaid class are the servedAirport if any, and the availability of the Navaid defined by one or more Timesheet (see Common coding patterns for details).

A Navaid may be used a SignificantPoint, e.g. for the start or end point of a route or terminal procedure or the centre point of a TAA/MSA, etc.

Each NavaidEquipment will have a location defined by the Point class. For certain NavaidEquipment an elevation has to be defined. In this case, the ElevatedPoint class has to be used (e.g. for DME).

This location of each of the NavaidEquipment of a Navaid may be the same (e.g. for a VOR/DME or a NDB collocated with a DME), or different (e.g. for a VOR/DME or the components of an ILS).

Also, the Navaid class itself may have a location. This is the location used when the navaid acts as a significant point (see also SignificantPoint (Overview)). This location is usually the location of one of the navaid equipments (e.g. in case of a VOR/DME it will be in general the location of the VOR).

The NavaidEquipment may also have a designator and a name, which in general will be the same as the one of the Navaid.

In addition, each NavaidEquipment may have a magneticVariation defined. Only VOR and TACAN have also a declination, i.e. the angular difference between True North and the station declination (Magnetic North - as indicated by the station).

Some NavaidEquipment have a frequency (e.g. VOR or NDB), whereas others have a channel defined (e.g. TACAN or DME).

Some NavaidEquipment have a defined magneticBearing and/or trueBearing (e.g. the measured angle between the localizer beam and Magnetic/True North at the localizer antenna).

Only the VOR has also a zeroBearingDirection, a code indicating the direction of the 'zero bearing' provided by the station. For example: magnetic north, true north.

The Navaid class is also used to code landing systems (e.g. ILS, Localizer only, MLS). It will be comopsed of the corresponding instances of NavaidEquipment, e.g. Localizer, Glidepath, MarkerBeacon, DME, etc.). Finally, the Navaid and not its individual components isInstalledAt a RunwayDirection.

A NavaidEquipment isUnderResponsibilityOf an OrganisationAuthority.