Re: aiming point & touchdown point:
I have been wondering about the question of where you actually touchdown for quite some time now. If you fly a B737 and follow a nominal 3 degree GS then, if all things being equal, the 1000ft markers should be your aim point. And as jt stated, your aim point can never be your touchdown point (unless you like being unemployed). So where is your touchdown point? The Boeing FCTM states for a normal approach, when aiming at the 1000ft marker, 50ft TCH, Vref +5, and a flare producing a 'Boeing' landing gives you a flare distance 1000ft to 2000ft beyond the threshold. (Pg. 257 in Adobe, ref 6.9)
And looking at it's US & ICAO runway markings, (Pg. 256, ref 6.8) it paints the aim points 1500' to 1312' into the runway respectively, with touchdown zone markings 500'-2075' US and 492'-2952' min ICAO.
Now what exactly does this mean? Does it mean that you will make a safe landing so long as the wheels touch down within the touchdown zone? If you took a runway that was 8000 feet long and if you used the ICAO touchdown zone (3000ft) and landing at the far end of it, that's 37.5% of your runway eaten up already. Which takes up a fair chunk of the 60% you are allowed use for calculate your landing there in the first place.
Hopefully I haven't rambled too much...
However it is an interesting point and any useful answers would be appreciated - always helps when you see those aim points drift under the nose at 130+ knots...!
Cheers