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...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:
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| This definition does not take into account that also Airport Reference Points may be used as start or end point of a route segment. ARP is also not marked by the site of a radio navigation aid. |
In AIXM, a DesignatedPoint is a specialisation of a SignificantPoint.
Waypoint
ICAO Annex 11 defines waypoint exclusively in the scope of RNAV operations
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| PANS-AIM uses the term waypoint not exclusively in the RNAV context. Should be aligned with ICAO Annex 11. Although also the definition Annex 11 for significant point is not clear enough. It defines the three categories of significant points, but does not take into account Designated Points which are no Waypoints (i.e. have 5LCN but are not used in the RNAV context). |
In AIXM, the class DesignatedPoint is used 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.
The SegmentPoint.waypoint attribute allows to specify if the point is used for Area Navigation (RNAV) procedures/routes. The SegmentPoint class is a generalisation of the TerminalSegmentPoint and the EnRouteSegmentPoint.
Summary
The term significant point Significant Point is the most generic one. It includes designated points Designated Points, but also Navaids, etc. The term designated point Designated Point excludes navaids Navaids and all the other types of significant pointsSignificant Points. It includes, but is not limited to waypointsWaypoints. Often, a designated point Designated Point will have an official (ICAO 5 letter code name) designator. The term waypoint Waypoint should exclusively be used in the RNAV context.
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The figure below shows the main AIXM 5 classes used for the DesignatedPoint concept:
Basically, a DesignatedPoint is defined by a designator and a specified geographical location defined by the Point class. In addition, a name and a type (e.g. 'ICAO', 'COORD', 'TERMINAL') can be coded.
The position of a DesignatedPoint may additionally be specified by an AngleIndication and/or a DistanceIndication, from an appropriate navaid Navaid or another designated pointDesignated Point. The role of the related PointReference may be for example, an intersection, an along track distance, bearing/distance points, recommended navaid etc.
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 Designated Point designator is unique within all other designated points associated with the same aerodromeAerodrome/heliportHeliport. Typically, such points are used for RNAV procedures at that aerodromeAerodrome/heliportHeliport.
- RunwayCentrelinePoint
The designated point is over a Runway/FATO centreline point. - TouchDownLiftOff
The designated point is located above the centre of the TLOF.
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The figures below give a simple examples example of the encoding of designated points as published in an AIP in section ENR 4.4:
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