IO540
The DME will only show the pilot a reading down to 0.1nm but the FMC in an airliner sees the distance much more accuratly.
In my opinion IFR navigation will be all GPS with DME/DME back up in twenty years.................................now who has one of those Narco NS900 starnav's that the GA community did not understand (& buy) it was a system yeard ahead of its time.
(but I would interface it with a King DME!)