The figure below shows the main AIXM 5 classes used for the touch down and lift off (TLOF) concept.
The TouchDownLiftOff class is used for defining a load bearing area on which a helicopter may touch down or lift-off.
A TLOF may be situated on a Runway (of type equal-to 'FATO') or directly at an AirportHeliport (i.e. the TLOF may form an integral part of the FATO or be situated apart).
A TLOF is identified by its designator.
In addition, its dimension may be described by a length and a width.
The extend of the TLOF may also be described ba the ElevatedSurface class.
A TLOF may have a centre point. In AIXM 5, the aimingPoint property will be used to code the centre point by using the ElevatedPoint class.
The surface of a TLOF is encoded by using the SurfaceCharacteristics class (see also Surface Characteristics [SCH]).