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    Re: Choice of timepiece
    From: Richard B. Langley
    Date: 2009 Nov 14, 08:53 -0400

    Lu:
    You refer to your "WWVL clock." Think you mean WWVB. WWVL, which operated on 20/26 kHz,
    was decommissioned in 1972. However, WWVB does use WWVL's antenna. More info here:
     including a note that we might get an east-coast
    transmitter some day.
    -- Richard Langley
    
    Quoting Lu Abel :
    
    >
    > Frank:
    >
    > Not to start a controversy (especially with you!), but I'm looking at
    > heavens-above.com and its display is about seven seconds slower than
    > time.gov.  I suspect that while, as they claim, they have very accurate
    > time-keeping on their server, they're not compensating for propagation
    > delay across the Internet.
    >
    > I just held my WWVL clock up to the time.gov display and it looks like
    > my Internet time is a tiny fraction of a second faster than my clock.
    > Mis-estimate of the delay to my computer by time.gov, or a display lag
    > (ala Doug's Trimble) on the part of my
    > $5.00-on-sale-at-the-local-electronics-superstore clock??
    >
    > Lu
    >
    > frankreed{at}HistoricalAtlas.com wrote:
    > > Douglas Denny, you wrote:
    > > "I can understand too that modern GPS engines are going to calculate faster and so
    > give less delay - but nevertheless there is no excuse whatever that the display time
    > can, with no effort needed by the designer, be _exact_ and displayed as such or
    > flagged as U/S until correct.  It is really rather silly to have a piece of kit which
    > receives signals of time to within a few nanoseconds, knows it,  and cannot display
    > it accurately"
    > >
    > > But this is just a market demand issue (and market demand drives product
    > specifications, right?). The vast majority of GPS users are looking for position
    > information primarily, and the time from the device is just a bonus. Very few GPS
    > users require time accurate to the nearest five seconds, let alone the nearest tenth
    > of a second. Who would use that information in a handheld GPS unit or any unit
    > designed fundamentally for position-finding? Of course, there are entirely different
    > market segments out there, like mobile phone companies, for whom the exact time is
    > actually the most important product in the GPS signal. It all comes down to demand. I
    > agree that it's ironic that the exact time is in there, hidden away somewhere, but I
    > don't agree that it's "silly" we can't see it. It's like my previous cell phone which
    > had a GPS receiver and knew its position accurately but had no way to display it
    > (this was a marketing choice by the manufacturer and the service provider). But it
    > DID have extremely exact time displayed --accurate to the nearest tenth of a second
    > quite reliably. This was derived from the cell towers' clocks apparently, and
    > presumably the towers got it from specialty GPS hardware.
    > >
    > > On the other topic in this thread, Internet time can be very good. One of my
    > favorite older web sites, the satellite tracking site at www.heavens-above.com,
    > recently added a little tool that provides properly synchronized time accurate to
    > "better than" one tenth of a second. I tested it from my PC against WWV just tonight,
    > and it seemed to be that accurate. Then I tested the same web page from the web
    > browser in my current smartphone (two years old so therefore "a dinosaur"). That same
    > tool in the phone browser could not keep up. The initial time was about right, but
    > the ticking seconds after that were in some kind of time warp and fell thirty seconds
    > behind after one minute. The phone's internal time (not from the Internet) can be up
    > to fifteen seconds off which is not good enough for celestial navigation experiments,
    > but certainly good enough for any practical tasks I do in my day.
    > >
    > > -FER
    > >
    > >
    > >
    > >
    > > >
    > >
    >
    >
    > >
    >
    
    
    ===============================================================================
     Richard B. Langley                            E-mail: lang---.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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