[CF-metadata] airspeed

Jonathan Gregory j.m.gregory at reading.ac.uk
Thu Mar 24 05:05:06 MST 2005

Dear Chris, Chuck and all

Thanks for your further definitions. I now understand that "airspeed" means
"speed relative to the air"! So that is not in fact what I would call the
speed of the aircraft, which is the groundspeed. It's a good illustration of
how terminology is not obvious. For instance, why shouldn't "airspeed" mean
"speed *of* the air" or "speed (of the aircraft) *in* the air" = groundspeed?

In other cases, we have chosen standard names to be explicit rather than use
familiar jargon. Would it be acceptable to give airspeed a standard name of
"speed_wrt_air" (to be explicit) or would that seem obscure?

There's a different issue about the various "kinds" of airspeed (true,
equivalent, calibrated). It seems to me that speed wrt air is the quantity
that people want to know. The varieties of it are different approximations to
measuring it. They aren't setting out to measure different quantities. This
is like the other issue that Chris raised, about the different kinds of
latitude estimate (GPS, inertial, GPS-corrected inertial). In that case you
gave them all the same standard name (latitude) because they're all the same
quantity. Is this the approach we should take with CF in general? Or should
we also give standard names to different kinds of *measurement* (as distinct
from different physical quantities being measured)?

Anyone's views would be helpful!



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