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This information is not directly required by PANS-AIM. However, there are two main concepts where navaids are composed of more than one navaid component.

Navaid Collocation (e.g. VOR/DME, VORTAC)
Landing System (e.g. ILS, Localizer only system, MLS)

The AIXM 5 possibilities to code such information shall be elaborated in this topic.

The following diagram shows the classes and data types needed to encode that information.

AIXM 5.2 Improvements

A change proposal (AIXM-341) for the next AIXM 5.2 version has been approved by the AIXM Change Control Board, which adds additional values in CodeNavigationEquipmentBaseType.

The coding guidelines provided here are aligned with forward/backward conversion rules contained in the AIXM-341 Change Proposal.

AIXM 5 provides several values for the Navaid.type dedicated to code collocated navaids and navaid system consisting of several components. For this purpose, the CodeNavaidServiceType contains inter alia the following values:

Value	Description
'ILS_DME'	ILS with collocated DME. Collocation can be with the antenna or the loc.
'MLS_DME'	MLS with collocated DME.
'VORTAC'	VOR and TACAN collocated.
'VOR_DME'	VOR and DME collocated.
'NDB_DME'	NDB and DME collocated
'LOC_DME '	LOC and DME collocated.
'NDB_MKR'	Non-Directional Radio Beacon and Marker Beacon
'ILS'	Instrument Landing System
'MLS'	Microwave Landing System
'LOC'	Localizer.

In AIXM 5,the Navaid isComposedOf of one or more NavaidEquipment. The NavaidComponent class is used to indicates the navigation use for each instance of NavaidEquipment as a component of the navigation service provided by a Navaid.

For example, a DME is a NavaidComponent of an ILS system. The DME may be collocated with the Glidepath, which is also a NavaidComponent of the same ILS system.

The NavaidComponent.collocationGroup attribute is used to describe the collocation of the instances of NavaidEquipment composing the Navaid. All NavaidEquipment that have the same value for this property are collocated together. For example, for a collocated VOR/DME the VOR and DME navaid equipment will be assigned the same collocationGroup number equal-to '1'. An ILS might have a DME co-located with Glidepath both sharing collocationGroup number equal-to '1' and a NDB co-located with a MarkerBeacon both sharing collocationGroup number equal-to '2'.

The NavaidComponent.markerPosition is a code indicating the position, in a navaid landing system, of the markers situated on the centreline of a runway. For example: 'OUTER', 'MIDDLE',' INNER', etc.

Finally, the NavaidComponent.providesNavigableLocation attribute indicates if the navaid equipment used to specify the navigable location of the Navaid when the navaid is used as significant point. For example, if you have a VOR/DME that is collocated but does not have the same geographical position, the VOR most likely will be the NavaidEquipment that provides the navigable location.

VOR/DME

A DME may be co-located with a VOR. Such a VOR/DME will be coded as one instance of a Navaid with type equal-to 'VOR_DME', referencing two corresponding NavaidEquipment instances, a VOR and a DME.

For both NavaidEquipment the NavaidComponent.collocationGroup will be equal-to '1'.

If the VOR is the navigable location of the navaid when the navaid is used as significant point:

the NavaidComponent.providesNavigableLocation for the VOR will be equal-to 'YES' and the NavaidComponent.providesNavigableLocation for the DME will be equal-to 'NO'.

The VOR provides the bearing information, whereas the DME is used for the distance information.

For both the VOR and the DME the location will be coded. Their location may be exactly the same geographical position or differ in the range as defined by ICAO Annex 10:

a) for those facilities used in terminal areas for approach purposes ..., the separation of the VOR and DME antennas does not exceed 80 m (260 ft);
b) for purposes other than those indicated in a), the separation of the VOR and DME antennas does not exceed 600 m (2 000 ft).

For the DME, also the ElevatedPoint.elevation has to be coded.

The VOR.designator and the DME.designator will be identical.

VORTAC

A TACAN may be co-located with a VOR. Such a VORTAC will be coded as one instance of a Navaid with type equal-to ''VORTAC', with two corresponding NavaidEquipment instances, a VOR and a TACAN.

For both NavaidEquipment the NavaidComponent.collocationGroup will be equal-to '1'.

If the VOR is the navigable location of the navaid when the navaid is used as significant point:

the NavaidComponent.providesNavigableLocation for the VOR will be equal-to 'YES' and the NavaidComponent.providesNavigableLocation for the TACAN will be equal-to 'NO'.

When using a VORTAC for civil purposes, in general, the VOR provides the bearing information, whereas the TACAN is used for the distance information.

The VOR.designator and the TACAN.designator will be identical.

NDB collocated with DME

A DME may be co-located with an NDB. Such a co-location will be coded as one instance of a Navaid with type equal-to 'NDB_DME', with two corresponding NavaidEquipment instances, an NDB and a DME.

For both NavaidEquipment, the NavaidComponent.collocationGroup will be equal-to '1'.

If the NDB is the navigable location of the navaid when the navaid is used as significant point:

the NavaidComponent.providesNavigableLocation for the NDB will be equal-to 'YES' and the NavaidComponent.providesNavigableLocation for the DME will be equal-to 'NO'.

The NDB provides the bearing information, whereas the DME is used for the distance information.

NDB collocated with Marker Beacon

A Marker Beacon may be co-located with an NDB. Such a co-location will be coded as one instance of a Navaid with type equal-to 'NDB_MKR', with two corresponding NavaidEquipment instances, a NDB and a MarkerBeacon.

For both NavaidEquipment the NavaidComponent.collocationGroup will be equal-to '1'.

If the NDB is the navigable location of the navaid when the navaid is used as significant point:

the NavaidComponent.providesNavigableLocation for the NDB will be equal-to 'YES' and the NavaidComponent.providesNavigableLocation for the MarkerBeacon will be equal-to 'NO'.

The NDB provides the bearing information, whereas the MarkerBeacon is used for the range information.

ILS & Localizer System

See topic ILS & Localizer Only.

MLS

See topic MLS.

Coding Examples

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

No.

Description

XPath Expression

NAV-EX-01

VOR-EX-01

DME-EX-01

VOR/DME purpose enroute

//aixm:NavaidTimeSlice [@gml:id ='NAV_BOR'] |

//aixm:NavaidTimeSlice [@gml:id ='VOR_BOR'] |

//aixm:NavaidTimeSlice [@gml:id ='DME_BOR']

NAV-EX-05

NDB-EX-03

MKR-EX-01

NDB collocated with Marker Beacon

//aixm:NavaidTimeSlice [@gml:id ='NAV_SCN'] |

//aixm:NDBTimeSlice [@gml:id ='NDB_SCN'] |

//aixm:MarkerBeaconTimeSlice [@gml:id ='NDB_SCN']

NAV-EX-06

LLZ-EX-01

GPT-EX-01

NDB-EX-02

MKR-EX-02

MKR-EX-03

ILS with MM and LOM

//aixm:NavaidTimeSlice [@gml:id ='NAV_OXS'] |

//aixm:LocalizerTimeSlice [@gml:id ='LLZ_OXS'] |

//aixm:GlidepathTimeSlice [@gml:id ='GPT_OXS'] |

//aixm:NDBTimeSlice [@gml:id ='NDB_KL'] |

//aixm:MarkerBeaconTimeSlice [@gml:id ='MKR_OM27R'] |

//aixm:MarkerBeaconTimeSlice [@gml:id ='MKR_MM27R']

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