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For TLOF PANS-AIM requires some basic properties as part of the minimum AIP data set. These are

designator, centre point, length, width, surface type

The diagram below shows the AIXM classes, including the relevant data types, needed to encode that information:

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.

Example TLOF designator values could be: HELIPAD-A, HELIPAD-B; TLOF1, TLOF2; etc.

If there is just one TLOF , the Designator can be just "TLOF".

TLOF Centre Point (aimingPoint)


AIXM 5.1(.1)

In AIXM only the aiming point of a TLOF can be coded. Is the aiming point the same as the centre point of a TLOF?

AccordingICAO Annex 14, Volume II,

The geographical coordinates of the geometric centre of the TLOF and/or of each threshold of the FATO (where appropriate) shall be measured and reported to the aeronautical information services authority

...

An aiming point marking should be provided at a heliport where it is necessary for a pilot to make an approach to a particular point before proceeding to the TLOF.

The aiming point marking shall be located within the FATO.

This definintions give the impression that the aimig 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 idenpendent form a TLOF na d may also be marked and lighted. It seem that currently aiming point is not covered by AIXM 5. The workaround is to code that information in a Note.



A workaround is to code the centre point of the TLOF using the ElevatedPoint class linked by the hasAimingPoint relationship.

In case an aming point and a centre point shall be coded for the TLOF, the actual aiming point has to be coded as Note.

TLOF Dimension (lenght & width)

The TLOF dimension attributes are used to describe the physical dimension of a TLOF.

The TouchDownLifftOff.length ist he declared longitudinal extent of the TLOF.

The TouchDownLifftOff.width is the declared transversal extent of the TLOF.

AIXm 5.1(.1) issue

For both attributes a dedicated attribute to provide accuracy is missing

As a workaround the accuracy value for the length and width may be encodes as note for the correpsonding property.

Open Qustion circle TLOF

How shall a circle shape be coded? Diameter as length and width? Releation to Surface class missing?

Surface

For the TLOF PANS-AIM requires to provide the surface type.

In AIXM 5 the SurfaceCharacteristic.composition attribute is used to code the surface type, e.g. asphalt, concrete, grass, etc.

The SurfaceCharacteristic class groups together more attributes that model the characteristics of an airport surface, such as strength, material, etc.

For detailed information about the surface characteristic attributes & corresponding rules please refer to topic Surface Characteristic [SCH].

Coding Rules for Basic Data for TLOF


Coding Examples

TBD in the scope of the DONLON AIXM AIP dat set.

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