If you read Annex 14, you will find that the distances to the aim point and TDZ markings depend on runway length/LDA and not on the approach type. I'm guessing the source of the confusion is the fact that you'll be more likely to see NPAs to short runways.
The runway markings will not coincide with the GP beam runway interception point. I would assume this to be based on the assumption of longer runways mainly being served by larger aircraft, with larger separation between GS antennas, pilot eye points and wheels.
The VASI units will typically not be colocated with either. They'll be located such that the typical aircraft serving the runway will have on-path indications while on the GP. Shorter/smaller aircraft will see below path indications on short final. The aim point markings will be made to coincide with the VASI indications though.
However, this is irrelevant as it has nothing to do with the specifications for the ILS. The ILS beam
will lead to a point 15-18 m above the threshold (with caveats). If it doesn't, the facility is not compliant with Annex 10 and will not be approved during commissioning. For CAT II/III, that's a requirement. For CAT I, 15-18 m is a recommendation, but "ensuring [...] safe and efficient use of the runway served" is a 'shall'.
The fact remains: The location of the GP mast
is irrelevant. The GP will cross the threshold at 15-18 m, barring shoddy CAT I installations and short runways.
So ALD would be an FAA-ificiation of LDR, or is there a subtle difference? Don't really care to compare definitions at the moment. Yay, we can have the RNAV/PBN/RNP debacle all over again.
@I-2021,
thanks. That's a risky definition. The distance between the GP beam intersection with the runway and the point abeam the GP mast can vary significantly (think sideslope). Clearly, the former is what is of operational interest but yet they publish the latter. I wonder where Jepp got
their definition though, if it is an internal product or if it is based on official guidance somewhere...
I agree with your conclusions regarding operational use, even though I wonder about the legality of the figure in the maps. I'd hit the official publications first to see if there's an LDA in there that Jepp omitted.