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The prospect of global shutdown of UPS is one of the few rationales for
celestial nav, so don't ruin our excuses too thoroughly in the name of
truth :).  Also, GPS satellites could be targeted during war.

It's important to remember the difference between GPS time and UT1, and
to be careful about which time is displayed on the unit.  Especially if
that were switchable by the user, it could lead to errors during times
of stress.

Fred

On Mar 17, 2005, at 12:52 PM, Richard Langley wrote:

> 1) DoD cannot make the decision by themselves. It would have to come
> from the
> White House. And any such decision is highly unlikely. Even during
> 9/11, GPS
> was not shut down. Futhermore, with localized jamming capability, it
> could be
> argued that there is no real need for a global shutdown anyway.
> 2) Use of GPS for setting a time piece that would be used as a time
> reference
> for celestial observations seems to me to be quite valid.
> -- Richard Langley
>    Professor of Geodesy and Precision Navigation
>    and Contributing Editor, GPS World Magazine
>
> On Thu, 17 Mar 2005, Victor Garand wrote:
>
>> Richard,
>>
>> Dual use applies to many facilities but it should not be confused
>> with dual
>> control particularly where national defence is concerned. The bottom
>> line,
>> as we have all been reminded is that national security trumps ALL.
>>
>> In any case, it seems to me that the only legitimate introduction of
>> GPS on
>> this particular List is its use as a training aid (check) in
>> developing
>> proficiency in the area of celestial navigation.
>>
>> Vic
>>
>>
>> ----- Original Message -----
>> From: "Richard Langley" 
>> To: 
>> Sent: Thursday, March 17, 2005 7:58 AM
>> Subject: Re: Timekeeping and sight time records
>>
>>
>>> On Thu, 17 Mar 2005, Victor Garand wrote:
>>>
>>>> By the way, if you need an excuse to spend time on the subject of
>>>> celestial
>>>> navigation, don't forget that the GPS network is a DoD facility. I
>>>> understand that general access is officially at the discretion of
>>>> DoD
>>>> (national emergencies etc. could change the situation).
>>>
>>> Not correct. GPS is officially a dual-use system. See
>>> >> FactSheetSPACE-BASEDPOSITIONINGNAVIGATIONTIMING.pdf>.
>>>
>>> -- Richard Langley
>>>
>>> =====================================================================
>>> ==========
>>> Richard B. Langley                            E-mail: lang@unb.ca
>>> Geodetic Research Laboratory                  Web:
>>> http://www.unb.ca/GGE/
>>> Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506
>>> 453-5142
>>> University of New Brunswick                   Fax:      +1 506
>>> 453-4943
>>> Fredericton, N.B., Canada  E3B 5A3
>>>     Fredericton?  Where's that?  See:
>>> http://www.city.fredericton.nb.ca/
>>> =====================================================================
>>> ==========
>>>
>>
>
>
> =======================================================================
> ========
>  Richard B. Langley                            E-mail: lang@unb.ca
>  Geodetic Research Laboratory                  Web:
> http://www.unb.ca/GGE/
>  Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506
> 453-5142
>  University of New Brunswick                   Fax:      +1 506
> 453-4943
>  Fredericton, N.B., Canada  E3B 5A3
>      Fredericton?  Where's that?  See:
> http://www.city.fredericton.nb.ca/
> =======================================================================
> ========
>

   

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