As NM says the current hourly regional QNH should be typed into the radar database. All acft flying away from the circuit below the TA would be on this If memory serves me corectly, the controller will then see an altitude relevant to that setting. Cant remember exactly how the computer assimilated the altitude of acft above this. I think that what you saw was always displayed relative to the QNH value entered just that above 3000, the altitude had a 0 put in front of it to show a FL?
Anyone??
As to whether its verified or not the give away used to be in the ATC phraseology. If the conflicting traffic was wearing a known SSR code then its vertical position would be described to you using the term :
" ....AT 3000 etc"
If however the SSR was unknown i.e 7000 then the term :
"... INDICATING 3000 etc" was used.
Was 10 years ago though so things in the UK (MIL) may have changed.
DogGone
