For the record,
In the interest of keeping this thread alive, suffice it to say that, for instance, the merits of accurate altitude information provided by primary radar and the possible implications with regard to the mid-air collision were discussed on another thread in the Tech Log forum quite a while ago.
I did not read the thread refered to above, but I can confirm that normal primary radar, as used in a civilian environment, does
NOT provide any altitude data.
It is true that height finding equipment (used by the military in some locations) is able to determine height (above ground). This data is of no use to ATC at high levels, as there is no corrolation between the "pressure level" (what is seen by the flight deck crew & by ATC [after conversion]) and the raw radar (primary) return.
SID
(ATCO)