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Purpose and Scope

These pages contain the coding guidelines for the minimum and conditional data items related to the "Waypoint -  en-route" subject as defined in PANS-AIM.

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At the beginning of this page the different terms Designated Point, Significant Point and Waypoint which are used in the avaition domain shall be discussed.

Sigificant Point

A Significant Point is defined by ICAO Annex 11

A specified geographical location used in defining an ATS route or the flight path of an aircraft and for other navigation and ATS purposes.

Note.— There are three categories of significant points: ground-based navigation aid, intersection and waypoint. In the context of this definition, intersection is a significant point expressed as radials, bearings and/or distances from groundbasednavigation aids.

The term significant point is not defined In ANNEX 15 or PANS-AIM. However, the terms significant point and desiganted significant points occurs in several sections, especially in "ENR 3. ATS ROUTES" to define the route.

...coded designators or name-codes and the geographical coordinates ... of all significant points defining the route...

Section "ENR 4.4 Name-code designators for significant points" is used to publish a list of

...name-code designators (five-letter pronounceable “name-code”) established for significant points at positions not marked by the site of radio navigation aids...

In AIXM the SignificantPoint  class is defined as follows:

A link class that allows selecting between a navaid system, a runway point, an airport reference point, an aiming point or a fix designated point.

SignificantPoint accounts for a specified geographical location used to define an ATS route, the flight path of an aircraft or for other navigation/ATS purposes.

In AIXM the SignificantPoint class could be seen as a 'placeholder' for a Navaid, Runway Point (e.g. a Threshold Position), Airport Reference Point, Aiming Point of a TLOF, Designated Point or a simple Point in space. At a conceptual level, it simplifies the model by significantly reducing the number of relationships.

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Designated Point

A term that is only defined by AIXM. The 'Designated Point' definition is derived from the Significant Point definition, by difference:

A  geographical location not marked by the site of a radio navigation aid, used in defining an ATS route, the flight path of an aircraft or for other navigation or ATS purposes.

In AIXM a DesigantedPoint is a specialisation of a SignificantPoint.

Waypoint

The term waypoint is not used in AIXM but in ICAO documents:

ICAO Annex 11 defines waypoint exclusivly in the scope of RNAV operations

A specified geographical location used to define an area navigation route or the flight path of an aircraft employing area navigation.

Annex 11 defines waypoint as a kind of significant point (see definition above).

Also in ICAO Annex 15 and PANS-AIM the term waypoint is used in the RNAV context. Sections "ENR 3.3 Area navigation routes" states

in respect of waypoints defining an area navigation route, additionally as applicable:

a) station identification of the reference VOR/DME;

The term is also used in "ENR 3.6 En-route holding" without a particular reference to RNAV.

The requirement is for a detailed description of en-route holding procedures, containing:

1) holding identification (if any) and holding fix (navigation aid) or waypoint

Also PANS-AIMS includes the "Waypoint – en-route" subject as part the AIP data set without pointing to any RNAV context.

In Appendix 1 of PANS-OPS (Aeronautical Data Catalogue) the Waypoint subject is part of the ATS Route section, presuming that the term is applicable for all kind of ATS routes and not only RNAV routes!

In AIXM the class DesignatedPoint is used in order to model points that have an official (5 letter) designator, have specified coordinates and do not mark the position of a Navaid. This includes, but is not limited to, 'waypoints' as many Designated Points are used for purposes other than defining a RNAV route.

Summary

The term significant point is the most generic one. It includes designated points but also Navaids, etc. The term designated point excludes navaids. It includes but is not limited to waypoints. Often, a designated points will have an official (5 letter) designator. The term waypoints are exculsivly used in the RNAV context.

AIXM Model Overview

The figure below shows the main AIXM 5 classes used for the Designated Point concept:

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Every DesignatedPoint must have a designator and a specified geographical position. In addtion a name and a type (e.g. 'ICAO', 'COORD', 'TERMINAL') may be defined.

Designated points with an ICAO 5 letter code used for defining ATS routes sould be recorded as type equal-to 'ICAO'.

The position of a DesignatedPoint may additionally be specified by an AngleIndication and/or a DistanceIndication, from an appropriate Navaid.

AIXM 5 also provides the possibility to encode points which are used in the context of defining terminal procedures. For this purpose several relationships can be established:

• AirportHeliport
  The designated point designator is unique within all other designated points associated with the same aerodrome/heliport. Typically, such points are used for RNAV procedures at that aerodrome/heliport.

AIXM Model Overview

Coding Examples

See child pages.

Child Pages