[time-nuts] Traceability after loss of LORAN and WWVB

Scott McGrath scmcgrath at gmail.com
Sat Jun 1 15:02:22 EDT 2013


True

However with LORAN and to a lesser extent WWVB traceability process was well/known and documented and had been in place for decades and was easy to implement correctly     With GPS not so much especially with S/A. Supposedly the new satellites don't have S/A but since the GPS satellites are primarily military in nature how will precise positioning be denied in emergency situations.  Shut down L1?,  dither the signal ????  Or is S/A still there and how does a T/F user respond to GPS not running normally???

A colleague of mine runs a cal lab. Guy is a wizard with physical and electrical standards    

I run some of my gear there in exchange for calibration of my instruments as lab has temp / pressure / humidity controls for physical standards so we both benefit.

Since the demise of LORAN and WWVB (although d-PSKer may allow us to bring spectracoms and 117a's back.  

To achieve traceability we have been shipping our CS and some Rb standards under power to labs who have achieved traceability

This is is a pain to say the least.  The procedures currently are not well documented on achieving traceability in the age of GPS only.    

And it's also true that most people confuse traceability with adjustment.  In reality it's more of a chain of data with documented values all the way back to NIST or other national standards lab




Sent from my iPhone

On Jun 1, 2013, at 1:18 PM, Bob Camp <lists at rtty.us> wrote:

> Hi
> 
> On Jun 1, 2013, at 11:40 AM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
> 
>> On 06/01/2013 04:54 PM, Bob Camp wrote:
>>> Hi
>>> 
>>> At least the way I read the pdf's NIST seems to believe that GPS is legally traceable to NIST. It is the same "measure and then look up the data" sort of thing that LORAN used to be.  Took a while to read through them all…
>> 
>> However, just taking time from GPS does not achieve NIST traceability.
>> The NIST folks will point it out too.
>> 
>> You can achieve NIST traceability (or to any other NIH) if you do a whole bunch of things _right_ and in accordance with relevant standards. Few do.
> In the context of the original post - exactly the same was true of LORAN. To actually achieve traceability you needed to do this and that once you had your "observations". In reality the same is true of WWVB and WWV. None of them achieve traceability in the strict sense simply from the observation of their frequency or time.
> 
> Bob
> 
>> Cheers,
>> Magnus
>> 
>>> Bob
>>> 
>>> On May 31, 2013, at 4:37 PM, Charles P. Steinmetz<charles_steinmetz at lavabit.com>  wrote:
>>> 
>>>> Scott wrote:
>>>> 
>>>>> How are those of you dealing with traceability in the commercial space
>>>> 
>>>> The topic is known as "legal metrology."  Start here:
>>>> 
>>>> <http://www.nist.gov/traceability/nist_traceability_policy_external.cfm>
>>>> 
>>>> You need to click through lots of links to get the whole picture.  I believe the material is printed in the NIST Administrative Manual.
>>>> 
>>>> Other potentially helpful links:
>>>> 
>>>> <http://tf.nist.gov/general/pdf/2289.pdf>
>>>> 
>>>> <http://tf.nist.gov/seminars/2002%20NIST%20Seminar%20-%20Traceability%20and%20Legal%20Metrology.ppt>
>>>> 
>>>> <http://www.icllabs.com/pdfs/A2LA_P102%20Policy%20on%20Measurement%20Traceability.pdf>
>>>> 
>>>> <http://tf.nist.gov/general/pdf/1305.pdf>
>>>> 
>>>> 
>>>> Best regards,
>>>> 
>>>> Charles
>>>> 
>>>> 
>>>> 
>>>> 
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