DME

Introduction & Background

This topic contains only those PANS-AIM requirements relevant for a DME. For general PANS-AIM requirements valid for all kind of Radio navigation aids see topic Navaid [NAV] and subordinated pages.

A DME (Distance Measuring Equipment) is Ultra High Frequency (UHF) ground equipment that is used in conjunction with airborne equipment to determine distance between the airborne and ground equipment.

For a DME, PANS-AIM requires some specific properties as part of the minimum AIP data set. These are

identification, name, aerodrome served, hours of operation, ...channel, position, elevation, ...

In addition, PANS-AIM ENR 4.1 and AD 2.19/AD 3.18 state as requirement

...elevation of the transmitting antenna of DME to the nearest 30 m (100 ft);...

...If the operating authority of the facility is other than the designated governmental agency, the name of the operating authority shall be indicated in the remarks column. Facility coverage shall be indicated in the remarks column.

The diagram below shows the AIXM classes, including the relevant data types and code lists, needed to encode that information. The main class is the DME which is a specialisation of the NavaidEquipment.

DME Designator & Name

In general, a DME will carry a three-letter character identifier. The DME.designator attribute is used to code that data.

In case the DME is collocated with a VOR it will have same designator as the VOR.

The long name given to the DME is coded using the DME.name attribute.

DME Type

PANS-AIM does not require the type of the DME to be provided. However, PANS-AIM requires different accuracy values for the elevation of a DME depending on its type. As elevation for the DME is part of the minimum AIP data set the type has to be known. In AIXM, the type is coded using the DME.type attribute. The type defines the spectrum characteristics or accuracy of the DME. The list of values for the CodeDMEType class contains:

Aerodrome Served

See topic Basic Data for Navaid.

Hours of Operation

See topic Hours of Operation for Navaid.

DME Channel

The channel of the DME is coded using the DME.channel attribute.

The corresponding data type CodeDMEChannelType contains a list of values from '1X' to '126Y'.

In case a DME is collocated with a VOR, certain requirements have to be taken in into account regarding the frequency pairing. The DME operating channel shall be paired with the VHF channel and/or MLS angle frequency as given in ICAO Annex 10, chapter 3, Table A.

Position

In case a DME collocated with a VOR is physically located at the same position as the VOR, the geographic position (latitude and longitude) of the VOR is also the geographic position of the DME.

In case a DME is collocated with a VOR and the position of the DME is different from the position of the VOR, some restrictions have to be taken into account (see Coding Rules below).

In case a DME is collocated with a VOR, unless otherwise specified, the published elevation (if any) refers to the DME. Thus, the elevation should be specified for the DME only.

For more details see topic Navaid Position & Elevation.

Elevation

PANS-AIM requires for the DME an elevation to be coded. The DME.location will be coded with the ElevatedPoint.elevation attribute.

Depending on the type of DME, different accuracy is required.  In AIXM, the ElevatedPoint.verticalAccuracy attribute is provided for that purpose (according to PANS-AIM Appendix 1, Table A1-5, for DME.type equal-to 'PRECISION' 3m accuracy is required; for all other types it is 30m (100ft)).

The ElevatedPoint.verticalDatum should be used to encode the corresponding information (e.g. 'EGM_96').

Operating Authority

See topic Operating Authority for Navaid.

Facility Coverage

See topic Facility coverage.

DME Displacement

This information is not required by PANS-AIM for the AIP data set, but often published in State AIPs. Also, ARINC 424  contains a data field for the "VHF NAVAID" record type for "ILS/DME" Bias.

The DME.displace attribute is used to code the distance from the DME antenna to the position where the zero-range indication occurs in the DME receiver.

It is relevant for DME used in the scope of an ILS installation.

Ghost Frequency

Although not required by PANS-AIM, a "ghost frequency" will be coded in case of a stand-alone DME.

The DME.ghostFrequency is used to code the frequency of a virtual VHF facility paired with the DME according to ICAO Annex 10.

Navaid Collocation

A DME may be co-located with one and only one VOR or NDB. In this case the corresponding Navaid feature will reference the DME as navaidEquipment.

In the AIP, collocated VOR and DME Navaids are usually referred to as VOR/DME or DVOR/DME.

There are certain ICAO rules regarding the relative distance between the VOR and the DME, frequency pairing and coded identifier. They are mentioned as coding rules.

A DME (and VOR) may only maintain a single collocation relationship at a time, which means that it is not possible to collocate a VOR with two different DMEs, and vice versa. The same is valid for a DME and NDB collocation.

A particular DME may also be defined as a part (NavaidEquipment) of a Navaid of  type 'ILS' or 'MLS'. A single DME can be part of more than one ILS/MLS, but each ILS can have just one assigned DME.

For more details see Landing Systems & Navaid Collocation.

Coding Examples

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

References