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The current list of values for declared distance types (CodeDeclaredDistanceType) includes 'DTHR' (thereshold displacement). This is expected to be deprecated in the next AIXM version (raised as issue AIXM-397 in the CCB), because it is incorrect from the ICAO Annex 14 point of view, which has a very precise list of declared distance types and how they are calculated/declared. Also, a THR displacement could also be negative, if the displacement is outbound, which cannot be coded uisng the 'DTHR' type. Therefore, a simple annotation is proposed to be used for the displacement value. |
In case also distance for the displacement shall be coded the RunwayDeclaredDistance class is used.
For this purpose the DeclaredDistance.type will be encoded equal-to 'DTHR'.
The actual displacement is encoded using the distance and distanceAccuracy attribute of the DeclaredDistanceValue class. This is a positive numerical value and it implies that the THR displacement is always inwards.
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Example EEKA: The coordinates of the displaced threshold are published (RWY 32) and the distance is published. Example LFCR: The coordinates of the displaced threshold and the threshold(!) are published (RWY 31) but no distance. |
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A declared distance is always related to a RunwayCentrelinePoint, which is the position along the runway centreline from where that distance is calculated. For aircraft performace calculations it is very important to know the exact position from where the declared distance was calculated. While the landing distance (LDA) is normally starting at the THR (or the displaced THR, if applicable), the take-off distances are starting from a centreline alignment point, which may be different from the thershold. Therefore, it is recommended to use two different RunwaCentrelinePoint for take-off and respectively landing declared distances, as indicated in the table below.
on the DeclaredDistance.type, the related RunwayCentrelinePoint will have a certain role (see also page Basic Data for Runway (FATO) Direction).
The table below gives an overview the type of a declared distances and the role of a runway centreline point that will usually be related to it.
DeclaredDistance.type | RunwayCentrelinePoint.role |
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'TORA' | 'START_RUN' |
'TODA' | 'START_RUN' |
'ASDA' | 'START_RUN' |
'LDA' | 'THR' or 'DISTHR' |
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