[time-nuts] IEEE Spectrum - Dec 2017 - article on chip-scale atomic frequency reference

[Magnus Danielson]

Hi,

On 12/09/2017 09:13 PM, Bob kb8tq wrote:
> Hi
> 
> I suspect that at the practical level, you define standard atmospheric pressure, standard
> gravity, standard magnetic field ….. and on down the list. At some point “sea level” becomes
> a redundant expression.

The standard acceleration is internationally agreed at 3rd CGPM in 1901 
to be 9.80665 m/s^2. So, that is "sea level". See SI brochure, I used 
version 8 in english, page 143.

This is also the standard value I have in my calculators and used for 
all my acceleration calculations.

In practice labs have their contributions into EAL/TAI corrected for 
their deviation from "sea level" for proper frequency of TAI.

Cheers,
Magnus

> Bob
> 
>> On Dec 9, 2017, at 2:14 PM, Mark Sims <holrum at hotmail.com> wrote:
>>
>> In the standards definitions that include "at sea level", the question these days is "which sea level?".  As ocean temperature changes sea level will change (except maybe in Washington DC).  Will the standards be amended to include something like "at sea level in 1990" or will the value being defined drift around with the changing sea level?
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