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Thanks Fred.

I apologize again for having apparently opened a can of worms with a simple
question. Since I will be away for some time, I look forward to rejoining
the list when I return.


----- Original Message -----
From: "Fred Hebard" 
To: 
Sent: Thursday, March 17, 2005 11:52 AM
Subject: Re: Timekeeping and sight time records


> 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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