[time-nuts] Accurate 1 pps signals

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Wed Aug 19 16:23:41 UTC 2009


> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Mark Sims
> Sent: Wednesday, August 19, 2009 8:56 AM
> To: time-nuts at febo.com
> Subject: [time-nuts] Accurate 1 pps signals
> 
> Know where the heck you are down to a gnats ass and get that location
> into the unit with full accuracy.   Errors in the saved antenna
> position from its true position have a definite effect on the quality
> of the output.  Ideally have the antenna location surveyed in WGS84
> coordinates.
> 


OK.. just what is a gnat's ass in actual SI units?

It's small.. 
Is it a standardized unit drawn from physiology (like the yard or foot, relative to King John's physical dimensions, or the cubit)
Is it a traditional term for some other standard unit (e.g. a "barn" being 1E-24 cm^2 or a shake being 1E-8, both being from early nuclear weapons development, and essentially a rounded value for some useful size: cross-section for a nuclear reaction, and generation time for fission, respectively) (I understand from some casual googling that the gnat's ass is used by machinists to refer to a tenthousandth of an inch/tenth of a mil, although none of the machininsts I know use the term. They talk in tenths when being quantitative, and have somewhat earthier terms when talking qualitative)

What I did find with google was interesting.. I didn't know that gnat's ass as a term for very small dated at least back to Aristophanes, although the lines 160-164 in Clouds are still qualitative, not quantitative (narrow, thin/subtle: stenos, leptos)

Next up, we need to decide which species of gnat is being referred to..



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