reynoldsno1:
I would expect it to be co-located with the GP aerial - TCH is 52ft or 15.85m. With 3 deg GP, GP origin is at 15.85/tan 3 deg = 302.4m (0.16NM) after the THR.
I would agree.
The FAA does it differently. When an ILS has a DME it is generally located to the side of runway near the far end.
Then, some countries bias the ILS DME to read zero at the threshold.