Navaid Position & Elevation

PANS-AIM requires as part of the minimum AIP data set the position for radio navigation and landing aids to be provided.

For some navaids (DME and GBAS), PANS-AIM also requires the elevation to be coded.  AD 2.19/AD 3.18:

...elevation of the transmitting antenna of DME ..., elevation of GBAS reference point...

The diagram below shows the AIXM classes relevant for the encoding.

To encode the position of a radio navigation or landing aid in AIXM 5, the ElevatedPoint class has to be used.

It is possible to code the location for both a Navaid and a NavaidEquipment:

• for the NavaidEquipment, the location shall be encoded as it defines where the navaid equipment resides.
• for the Navaid that can act as a significant point (See also topic SignificantPoint (Overview)), the navigable location shall also be encoded. For example, when the navaid is used as SegmentPoint for the start or end of a route segment, or a procedure leg.

In case the navaid is composed of several navaid equipments, the locations of the navaid equipments may be different. For example, the marker beacons and the glidepath of an ILS will have different locations than the localizer. Even in case of collocated navaids, such as a VOR/DME, the DME may be located at a different position than the VOR. In this regard, it is important to know, which of the navaid equipments is the one that provides the navigable position. In most cases this will be the navaid equipment providing azimuth information (e.g. in case of a VOR/DME the VOR). The NavaidComponent.providesNavigableLocation attribute is used to identify the corresponding NavaidEquipment.

For details about the encoding and rules for points, see the topic Geometry.

If required for a certain NavaidEquipment, the ElevatedPoint.elevation attribute will be coded.  The elevation attribute is used to provide vertical distance of the point measured from Mean Sea Level (MSL). In addition to that, the verticalAccuray and verticalDatum will be coded.

For the sake of conformity, to avoid ambiguity, and to support spatial queries, the Navaid.location shall always be encoded, even it is exactly the same as the one of the navaid equipment(s).

Coding Examples

See also topic Navaid [NAV].

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