[LEAPSECS] Crunching Bulletin B numbers (POSIX time)

[Richard B. Langley]

Quoting Warner Losh <imp at bsdimp.com>:


> On 02/23/2011 05:57, Richard B. Langley wrote:

>> For those who might not be aware. Loran-C in North America is dead.  

>> It might be resurrected as eLoran or some other LF service in the  

>> future:

>> http://www.ursanav.com/sites/default/themes/danland/images/buzz/pdfs/LF-Solutions-for-APNT-ION2011.pdf

>

> Well, eLoran was implemented in the North American chain a couple of  

> years before they started to shut it off.  Given that the stations  

> have been decommissioned and the towers blown up in at least some  

> places, I doubt it will ever resurrect.


The decision to terminate Loran-C in North America, leaving GPS  
without an effective backup there, was extensively covered in GPS  
World. eLoran was initiated but not completed. I had an article in my  
column about GPS plus eLoran before Loran-C got the chop:  
<http://www.gpsworld.com/transportation/road/innovation-gps-loran-c-6550>.
-- Richard


> But the requirements of that system, and how they interacted with  

> other requirements when coupled with inflexible military bureaucracy  

> shows that there's a wide diversity of requirements for some problem  

> domains that you don't run into with a server in a computing center.

>

> Warner

>

>>

>> -- Richard

>>

>> Quoting Ian Batten <igb at batten.eu.org>:

>>

>>>>

>>>> Nope.  tried that when getting the spec approved.  Approximate  

>>>> times weren't allowed.  UTC times were required.  There was no  

>>>> way to indicate approximate time in the user interfaces present  

>>>> (how do you blink a 5071A anyway :).  The other systems that  

>>>> interfaced to ours had a fixed format, and required UTC and not  

>>>> approximate UTC for a while and then a possible jump in time to  

>>>> actual UTC.

>>>

>>> Well, if the use-case is navigation (Loran, military) then UTC  

>>> sans leap seconds isn't much use to you anyway, so the "solution"  

>>> of dropping them would take your requirement with it, and you'd  

>>> seen something closer to UT1.  And of course, requirements are  

>>> simply line items on an invoice, and if deriving immediate UTC  

>>> costs 10X rather than X, the customer has to make a decision on  

>>> whether they're prepared to pay for it.  Just saying "my customer  

>>> demands X and therefore the rest of you need to enable X" isn't  

>>> realistic.

>>>

>>> ian

>>>

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>>

>>

>>

>> ----------------------------------------------------------------------------- | Richard B. Langley                            E-mail: lang at 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.fredericton.ca/       |

>> -----------------------------------------------------------------------------  

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>>

>>

>>

>

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>




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| Richard B. Langley                            E-mail: lang at 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.fredericton.ca/       |

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