On 9-Jul-2005, Newps wrote:

The controller almost always eyeballs it. As for range rings they are
alway displayed and are drawn around the radar site, not around an
individual airplane.


Of what possible use would range rings centered on the radar site be? From
my memory of a visit a few years ago to a TRACON facility, I seem to recall
that the controllers could get a reasonably accurate reading of distance
from given fixes (e.g. VORs, OMs, airfields, etc.) by calling up range rings
from that fix to appear on his/her scope. Given the level of digital
sophistication they have available on the newer technology radar displays,
that would be a piece of cake. Still, as you state, my guess is that most
controllers, particularly experienced ones, usually eyeball it unless more
precision is required.

--
-Elliott Drucker