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Introduction
For Route Segment, PANS-AIM requires some basic properties as part of the minimum AIP data set. This is
..., startpointfrom point, endpointto point, track, distance, upper limit, lower limit, MEA, MOCA, ...
The diagram below shows the AIXM classes, including the relevant data types, needed to encode that information:
Start Point & End Point
ICAO defines a route segment as
A portion of a route to be flown usually without an intermediate stop, as defined by two consecutive significant points.
In AIXM 5, the start and the end properties of the RouteSegment class are used to define the "From point", i.e. the first point of the route segment and "To point", i.e. the second point of a route segment.
The EnrouteSegmentPoint class used for that purpose is a specialisation of the SegmentPoint. It provides the reportingATC attribute which is used for the indication of the ATS / MET reporting requirement 'COMPULSORY' or 'ON_REQUEST' for the corresponding point.
The actual start or end point of a RouteSegment is defined via the pointChoice property that allows to select a SignificantPoint. Not all available choices of significant points (e.g. RunwayCentrelinePoint, etc.) will make sense to be used for a route segment point (see also page SignificantPoint [SPN] ).
Mainly DesignatedPoint and Navaid will be the start or end point of a RouteSegment. In a few countries, also the airport reference point of an AirportHeliport may be used for that purpose.
For defining that the point used for the route segment is an RNAV waypoint (see also topic Designated Point (Overview)) the EnrouteSegmentPoint.waypoint attribute will be encoded with 'YES'.
In addition, AIXM 5 provides as an option to encode the extend of the route segment as geometrical element, using the Curve class. This data may be used for charting purposes. The curve will be encoded according to the corresponding GML specification (see topic Geometry (Overview)). It will contain the coordinates of the start and end point of the route segment. It shall be ensured that the data (i.e. coordinates) provided in the Curve element(s) match with those provided as start and end of the RouteSegment.
Implicit direction
As every route segment is defined 'from' a start point 'to' an end point, it has an implicit direction. This direction should be consistent with the direction of the route. The start point of a route should also be the 'from' point of the first route segment and the end point of the route should be the 'to' point of the last segment.
The implicit direction of a route segment is relevant when specifying the route availability (see also page Direction of Cruise Levels).
Rules are included in the model to enforce consistency between the general direction of the route and the implicit direction of every segment (see below).
Track & Length
The RouteSegment class provides several attributes to define the initial trueTrack, initial magneticTrack, the initial reverseTrueTrack and the initial reverseMagneticTrack of it.
For "ENR 3.3 Area navigation routes", PANS-AIM explicitly requires that the magnetic bearing of the route segment is provided. For all other routes defined in ENR 3, PANS-AIM requires a track or VOR radial applying the following note
Bearings, tracks and radials are normally magnetic. In areas of high latitude, where it is determined by the appropriate authority that reference to Magnetic North is impractical, another suitable reference, i.e. True North or Grid North, may be used.
Tracks and reverse tracks if any, shall be encoded taking into account the implicit direction of the route segment, i.e. the defined start and end point, (see also above). In this regard, the tracks are from the start point of the segment, whereas the reverse tracks are from the end point of the route segment.
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AIXM 5.1.1 does not provide the possibility to define if the path between on the route segment is a VOR radial. Shall 'OTHER:VOR_RADIAL' for RouteSegment.pathType be used for that purpose? |
The length attribute allows to define the distance of the path of the RouteSegment. The length depends on the pathType, which may be a great circle ('GRC'), a rhumbline ('RHL') or a geodesic line ('GDS').
According to PANS-AIM, the length of a route segment shall be provided as geodesic distance.
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| PANS-AIM requires geodesic, in AIPs very often you will find great circle, in case of a conventional route defined by VORs would the path type not rather be a Radial? TBD in the FG |
PANS-AIM Appendix 1 also defines accuracy values the length. Also for the tracks but only for terminal arrival departure.
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AIXM 5.1(.1) does not provide a dedicated accuracy attribute for length. It can only be encoded using a corresponding annotation for the length attribute. |
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| title | PANS-AIM issue |
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A change proposal (AIXM-532) for the next AIXM 5.2 version has been approved by the AIXM Change Control Board, which adds direct associations from InformationService, AirTrafficControlService, AirTrafficManagementService, and SearchAndRescueService towards RouteSegment. The coding guidelines provided here are aligned with forward/backward conversion rules contained in the AIXM-532 Change Proposal. |
From Point & To Point
ICAO defines a route segment as
A portion of a route to be flown usually without an intermediate stop, as defined by two consecutive significant points.
In AIXM 5, the start and the end properties of the RouteSegment class are used to define the "From point", i.e. the first point of the route segment and "To point", i.e. the second point of a route segment.
The EnrouteSegmentPoint class used for that purpose is a specialisation of the SegmentPoint. It provides the reportingATC attribute which is used for the indication of the ATS / MET reporting requirement 'COMPULSORY' or 'ON_REQUEST' for the corresponding point.
The actual start or end point of a RouteSegment is defined via the pointChoice property that allows to select a SignificantPoint. Not all available choices of significant points (e.g. RunwayCentrelinePoint, etc.) will make sense to be used for a route segment point (see also page SignificantPoint [SPN] ).
Mainly DesignatedPoint and Navaid will be the start or end point of a RouteSegment. In a few countries, also the airport reference point of an AirportHeliport may be used for that purpose.
For defining that the point used for the route segment is an RNAV waypoint (see also topic Designated Point (Overview)) the EnrouteSegmentPoint.waypoint attribute will be encoded with 'YES'.
In addition, AIXM 5 provides as an option to encode the extend of the route segment as geometrical element, using the Curve class. This data may be used for charting purposes. The curve will be encoded according to the corresponding GML specification (see topic Geometry (Overview)). It will contain the coordinates of the start and end point of the route segment. It shall be ensured that the data (i.e. coordinates) provided in the Curve element(s) match with those provided as start and end of the RouteSegment.
Implicit direction
As every route segment is defined 'from' a start point 'to' an end point, it has an implicit direction. This direction should be consistent with the direction of the route. The start point of a route should also be the 'from' point of the first route segment and the end point of the route should be the 'to' point of the last segment.
The implicit direction of a route segment is relevant when specifying the route availability (see also page Direction of Cruise Levels).
Rules are included in the model to enforce consistency between the general direction of the route and the implicit direction of every segment (see below).
Track & Length
The RouteSegment class provides several attributes to define the initial trueTrack, initial magneticTrack, the initial reverseTrueTrack and the initial reverseMagneticTrack of it.
For "ENR 3.3 Area navigation routes", PANS-AIM explicitly requires that the magnetic bearing of the route segment is provided. For all other routes defined in ENR 3, PANS-AIM requires a track or VOR radial applying the following note
Bearings, tracks and radials are normally magnetic. In areas of high latitude, where it is determined by the appropriate authority that reference to Magnetic North is impractical, another suitable reference, i.e. True North or Grid North, may be used.
Tracks and reverse tracks if any, shall be encoded taking into account the implicit direction of the route segment, i.e. the defined start and end point, (see also above). In this regard, the tracks are from the start point of the segment, whereas the reverse tracks are from the end point of the route segment.
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AIXM 5.1.1 does not provide a dedicated value to define if the path between on the route segment is a VOR radial. 'OTHER:VOR_RADIAL' may be used for RouteSegment.pathType. |
The length attribute allows to define the distance of the path of the RouteSegment. The length depends on the pathType, which may be a great circle ('GRC'), a rhumbline ('RHL') or a geodesic line ('GDS').
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| According to PANS-AIM, the length of a route segment shall be provided as geodesic distance. |
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PANS-AIM defines an accuracy for the values for the length of an Route Segment. There is no dedicated attribute in AIXM 5.1.1. Workaround fro AIXM 5.1(.1): A Note may be used to encode that information. Status AIXM 5.2: See CCB AIXM-269. |
Lateral Limits
For "ENR 3.1 Lower ATS routes" and "ENR 3.2 Upper ATS routes", PANS-AIM requires the provision of lateral limits.
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| PANS-AIM | AIXM 5.1.1 | Remarks | ||||||||||||||||||||||||||||
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| Property | Definition/Description | Relevance | Attribute | Description | ||||||||||||||||||||||||||
| Upper limit | The upper limit of the route segment | ENR 3.1-3.4 | upperLimit | The vertical position of the route segment ceiling. | ||||||||||||||||||||||||||
| Lower Limit | The lower limit of the route segment | ENR 3.1-3.4 (Note 2) | lowerLimit | The vertical position of the route segment floor. |
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| Minimum obstacle clearance altitude (MOCA) | The minimum altitude for a defined segment of flight that provides the required obstacle clearance. minimumObstacleClearingAltitude | ENR 3.1 Lower ATS Route | minimumObstacleClearanceAltitude, RouteSegment.annotation.Note.propertyNamevalue equal-to 'minimumObstacleClearanceAltitude' | Minimum obstacle clearance altitude (MOCA). The minimum altitude for a defined segment of flight that provides the required obstacle clearance. | According to ICAO PANS-OPS
In PANS-AIM it is only required for ENR 3.1 Lower ATS Routes. The MOC value to be applied in the primary area for the en-route phase of an IFR flight is 300 m (1 000 ft) as a minimum.
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| Minimum en-route altitude (MEA) | The altitude for an en-route segment that provides adequate reception of relevant navigation facilities and ATS communications, complies with the airspace structure and provides the required obstacle clearance. | ENR 3.1 Lower ATS Route (Note 2) | minimumEnrouteAltitude, RouteSegment.annotation.Note.propertyNamevalue equal-to 'minimumEnrouteAltitude' | Minimum en-route altitude (MEA). The altitude for an en-route segment that provides adequate reception of relevant navigation facilities and ATS communications, complies with the airspace structure and provides the required obstacle clearance. | According to ICAO PANS-OPS
| Minimum flight
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| Minimum flight altitude | Minimum flight altitude | ENR 3.4 Helicopter routes | | Warning |
AIXM does not have a dedicated attribute for that purpose. Info |
Open Question TBD: Is Minimum flight altitude the same as the MEA or MOCA for fixed wing but for helicopters? Is "Minimum flight altitude" defined somewhere? Until clarified, mapped to MOCA. minimumObstacleClearanceAltitude, RouteSegment.annotation.Note.propertyNamevalue equal-to 'minimumObstacleClearanceAltitude'According to PANS-AIM
In PANS-AIM the term is only used for "ENR 3.4 Helicopter routes" ICAO Annex 11, 2.23 Minimum flight altitudes Minimum flight altitudes shall be determined and promulgated by each Contracting State forminimumObstacleClearanceAltitude, RouteSegment.annotation.Note.propertyNamevalue equal-to 'minimumObstacleClearanceAltitude' | According to PANS-AIM
In PANS-AIM the term is only used for "ENR 3.4 Helicopter routes" ICAO Annex 11, 2.23 Minimum flight altitudes
| NA | NA | NA | minimumCrossingAtEnd | The lowermost vertical position at the end point, when flying on the route portion in the direction indicated in the RoutePortionUsage. | |||||||||||||||||||
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RoutePortionUsage is not defined in AIXM 5.1.1. If this attribute is related to the route portion, why is it part of the RouteSegment class? |
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| PANS-AIM defines more vertical limits, i.e. Area Minimum Altitude (AMA) and Minimum Vectoring Altitude (MVA) which are not considered as part of the AIP Data set and hence are not contained in the table. |
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In some State AIPs, an additional limit, "overriding" the Lower limit specification is published. To publish this minimum limit, often statements such as " but at least" are used. The Lower limit override always refers to ground e.g. "feet above ground". How to encode this in AIXM 5.1.1? in AIXM 4.5, a dedicated attribute was provided VAL_DIST_VER_LOWER_OVRDE Example:
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Regarding the general encoding guidelines and rules for vertical limits see topic Vertical Limits.
Level
Although this information is not explicitly required by PANS-AIM it should be coded at least for route segments published in an AIP in Section ENR 3.1 Lower ATS routes and ENR 3.2 Upper ATS Routes, with 'LOWER' and 'UPPER' respectively.
Coding Rules for Basic Data for Route Segment
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RouteSegment.start.EnRouteSegmentPoint.reportingATC is mandatory.
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| If the route segment is only flown BACKWARD, will the track flown be considered to be "track" or the "reveres track"? |
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minimumObstacleClearanceAltitude is mandatory for ENR 3.1 Lower ATS Routes
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To be clarified if also for ENR 3.4 Helicopter routes. Based on the open question for Minimum flight altitude property. |
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| This rule is suspended until clarified how PBN specification requirements are finally defined in PANS-AIM. |
See also rule RSG-101
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AIXM-5.1_RULE-F07AB
(Rule does not take into account UNL)
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RouteSegment.upperLimit shall not be equal-to 'FLOOR' or 'CELLING' or 'GND'.
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AIXM-5.1_RULE-F07AC
(Rule does not take into account GND)
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AIXM-5.1_RULE-F07A9
(Rule does not take into account UNL)
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AIXM-5.1_RULE-F07AA
(Rule does not take into account UNL)
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Each RouteSegment shall have assigned routeFormed value.
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Two consecutive route segments (of the same Route) should have vertical limits that, if not overlapping, should not be further away than 1000 FT. For example, if segment 1 is FL245 to FL295 and segment 2 is FL310 to FL490, (this rule will need to be adjusted based on operational experience).
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The angle between two consecutive segments of the same route cannot exceed 90 degrees.
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TBD
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| This rule is based on the areas of responsibility defined in EAD. Shall there be a similar rules for the AIP data set based e.g.on FIR/UIR? |
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According to the rule definition the rule is violated, because four significant points "KPT", "TGO", "KRH" and "ECCHO" are used only once, either as start or end point of a route segment.
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In the given example the rule is violated, because route segment "ECCHO - ANEKI" is described in the opposite order of the adjacent segments.
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According to the rule definition the rule is violated, because ANEKI appears on three route segments.
Subsequently this results in multiple branches; "ANEKI - ECCHO" and ANEKI - RUDUS".
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The position of the SignificantPoint used as the beginning of the RouteSegment must be separated by at least 30m (1 sec of arc) from the position of the SignificantPoint used as the end of the RouteSegment.
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| Is this rule justified by an ICAO doc? |
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The value of EnRouteSegmentPoint.reportingATC for RouteSegment.start and RouteSegment.end of any two consecutive segments of the same route must be consistent.
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The difference between length and the calculated length of the related RouteSegment cannot exceed 5 KM.
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| PANS-AIM requires an accuracy of 1/10 KM. Shall the rule be changed accordingly? |
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The difference between Initial trueTrack and the calculated initial true track of the related RouteSegment cannot exceed 2 degrees.
The difference between reverseTrueTrack and the calculated reverse initial true track of the related RouteSegment cannot exceed 2 degrees.
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Regarding the general encoding guidelines and rules for vertical limits see topic Vertical Limits.
Level
Although this information is not explicitly required by PANS-AIM it should be coded at least for route segments published in an AIP in Section ENR 3.1 Lower ATS routes and ENR 3.2 Upper ATS Routes, with 'LOWER' and 'UPPER' respectively. This is also relevant as some Coding Rules relate on this information (see below).
Coding Examples
The figure below gives a simple example of the encoding of the route segment from "DINKI" to "LNO".
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More coding examples can be found in the AIXM DONLON AIP data set AIP Data Set - Specimen (DONLON).
| No. | Description | XPath Expression |
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RSG-EX-01 RSG-EX-04 | Route segment of Lower ATS route (incl. MEA) Route segment of Lower ATS route (incl. MOCA) | //aixm:RouteSegmentTimeSlice[@gml:id='RSG_A6_BOR_ROB'] | //aixm:RouteSegmentTimeSlice[@gml:id='RSG_A6_ROB_ROK'] |
| RSG-EX-02 | Route segment of Upper ATS route | //aixm:RouteSegmentTimeSlice[@gml:id='RSG_UA4_BARIM_WOB'] |
| RSG-EX-03 | Route segment of RNAV route | //aixm:RouteSegmentTimeSlice[@gml:id='RSG_UL123_ABOLA_ILURU'] |
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