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Introduction
For TLOF, PANS-AIM requires some basic properties as part of the minimum AIP data set. These are
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The diagram below shows the AIXM classes, including the relevant data types, needed to encode that information:
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A change proposal (AIXM-561) for the next AIXM 5.2 version has been approved by the AIXM Change Control Board, where the helicopterPerformanceClass attribute is added to AircraftCharacteristics and the association between TouchDownLiftOff and AircraftCharacteristic is established. The coding guidelines provided here are aligned with forward/backward conversion rules contained in the AIXM-561 Change Proposal. |
TLOF Designator
The TouchDownLiftOff.designator attribute represents the textual designator of the TLOF, used to distinguish physical TLOFs at an Aerodrome/Heliport that has more than one. The attribute value should reflect the local convention for physical TLOF naming at the Aerodrome/Heliport.
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PANS-AIM requires the centre point of the TLOF to be provided including its elevation and geoid undulation.
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In AIXM, only the aiming point of a TLOF can be coded. Is the aiming point the same The aiming point is not the same position as the centre point of a TLOF?. According to ICAO Annex 14, Volume II,
This definitions give the impression that the aiming point is not the centre point of the TLOF. Currently in AIXM, it is not possible to define the two different points for a TLOF. Anyhow, it seems that the relationship hasAimingPoint and the property TLOF.aimingPoint is not correct. It should be rather hasCentrePoint and TLOF.centrePoint. Also, an aiming point may be independent from a TLOF and may also be marked and lighted. It seems that currently aiming point is not covered by AIXM 5. The workaround is to code that information in a Note. |
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The relationship hasAimingPoint and the property TLOF.aimingPoint were incorrectly named in AIXM, as the real intention was to model the TLOF centre point. The aiming point is more appropriately modelled as a RunwayCentrelinePoint, because it is always on a FATO (which in AIXM is modelled as a Runway of type FATO). Therefore, the following workaround is used in AIXM 5.1(.1):
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The ElevatedPoint class provides also dedicated attributes for elevation and geoidUndulation.
In addition the horizontal and vertical accuracy defined by PANS-AIM may be coded using the horizontalAccuracy and verticalAccuracy attribute.
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In AIXM 5 the verticalAccuracy refers to both the elevation and the geoidUndulation.
Hence, if the verticalAccuracy is coded for the elevation but the accuracy for the Geoid undulation is not known, this should be put into a corresponding Note.
TLOF Dimension (length & width)
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| For both attributes a dedicated attribute to provide accuracy is missing in AIXM 5. | ||
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PANS-AIM defines an accuracy for the TLOF length and width. AIXM 5.1.1 does not have dedicated attributes for that purpose. Workaround for AXM 5.1(.1): As a workaround, the accuracy value for |
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the length |
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and width |
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may be encoded |
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as annotation |
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for the corresponding property. Status: see CCB AIXM-269 |
In addition the extend of the TouchDownLiftOff may be coded using the ElevatedSurface class. In case of a rectangular shape the defined extend (by a set of points with latitude longitude information) shall be consistent with the provided length and width values.
In many cases the shape of a TLOF will be a circle rather than a rectangular. In such case the length and width may not be coded (although required as minimum data for the AIP data set). In such cases only the extend shall be coded, using the corresponding gml element for a circle (see document 12-028_Use_of_GML_for_aviation_data-2.pdfelements of the Surface class (see also Geometry).
Surface Type (composition)
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In addition, a TLOF may be situated on a Runway. In this regard a runway may be of type Runway or FATO (see also topic Runway [RWY]).
Coding Rules for Basic Data for TLOF
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AIXM-5.1_RULE-D6D8E
(rule does not take into account PinS approach constraint)
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The aimingPoint property is used to actually code the centre point, see also AIXM 5.1(.1) issue above.
PANS-AIM requires 0.5 m for the Elevation & the Geoid undulation.
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PANS-AIM Appendix 1 states :
For heliports intended to be operated in accordance with ICAO Annex 14, Appendix 2
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| It is not clear what is meant by that statement? |
PANS-AIM requires 0.25 m for the Elevation & the Geoid undulation.
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AIXM-5.1_RULE-D9C62
Note: the only think that can be verified in this case is the use of either FT or M as unit on measurement. A value such as "200 M" cannot be assumed to break this rule because maybe this is the exact elevation value.
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AIXM-5.1_RULE-4611A
Note: the only think that can be verified in this case is the use of either FT or M as unit on measurement. A value such as "200 M" cannot be assumed to break this rule because maybe this is the exact elevation value.
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AIXM-5.1_RULE-E681,
AIXM-5.1_RULE-E682
(2nd rule checks 3.0 FT which is not defined in PANS-AIM)
This association should also be used in order to associate a TLOF with a Runway that is used for final approach by helicopters, while the TLOF itself is located somewhere else on the airport surface. In this regard a runway may be of type Runway or FATO (see also topic Runway [RWY]).
Coding Examples
Coding examples can be found in the DONLON AIXM 5.1.1 AIP data set file AIP Data Set - Specimen (DONLON):
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| TLA-EX-01 | TLOF (rectangular shape defined by with length/width and extend) | //aixm:TouchDownLiftOffTimeSlice[@gml:id ='TLA_EADH_TLOF'] |