to visualize the difference between the 2 values let's consider a practical example. DTM RWY 06. RWY physical length 6562 ft landing beyond the THR 5577 which is the same as TORA from B. LDA beyond the GS is 4454 ft. Needless to say the runway is limiting here. Let's assume you're conducting a CAT II approach with an auto land on RWY 06 dry, 0 wind on A 320 with 60 tons LW. Let's crunch the numbers: Autoland distance with configure full, auto brake MED is 1440 meters = 4724 ft. According to your thesis we're good to go coz we're well within 5577 whereas I say nope, can't do coz I'll be over my LDA beyond the GS by 270 ft. Interesting to hear other opinions.
