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Rest Clocks

 
 
John McWilliams
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      10-29-2006
Mike Fields wrote:
>
> Almost forgot to "rest" the clock in my GPS !!


That's frightening. The having a GPS that needs to have its time set
manually, that is.

What make and model?

--
john mcwilliams
 
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MarkČ
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      10-29-2006
Mike Fields wrote:
> "Ray Fischer" <(E-Mail Removed)> wrote in message
> news:4544f26a$0$34491$(E-Mail Removed)...
>> Ed Ruf (REPLY to E-MAIL IN SIG!) <(E-Mail Removed)> wrote:
>>> That time of year for many of us again.

>>
>> ... when clocks get really tired and need to be "rested" for an hour.
>>
>>
>>
>> --
>> Ray Fischer
>> http://www.velocityreviews.com/forums/(E-Mail Removed)
>>

>
> Of course there was that scene from the movie "Animal House"
> (for those old enough to remember it) where they were staging
> a raid and synchronizing their watches -- they were all at 11:00
> or some such "exactly" except for John who was at 3:17 or some
> such time .. OK, good to go !!
>
> Almost forgot to "rest" the clock in my GPS !!


Any GPS unit I've ever used set itself... I don't even think you could set
it to a different time if you wanted to...

--
Images (Plus Snaps & Grabs) by MarkČ at:
www.pbase.com/markuson


 
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Prometheus
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      10-30-2006
In article <JFa1h.64$(E-Mail Removed)>, MarkČ
<mjmorgan@cox.?.net.invalid> writes
>Mike Fields wrote:
>> "Ray Fischer" <(E-Mail Removed)> wrote in message
>> news:4544f26a$0$34491$(E-Mail Removed)...
>>> Ed Ruf (REPLY to E-MAIL IN SIG!) <(E-Mail Removed)> wrote:
>>>> That time of year for many of us again.
>>>
>>> ... when clocks get really tired and need to be "rested" for an hour.

>>
>> Of course there was that scene from the movie "Animal House"
>> (for those old enough to remember it) where they were staging
>> a raid and synchronizing their watches -- they were all at 11:00
>> or some such "exactly" except for John who was at 3:17 or some
>> such time .. OK, good to go !!
>>
>> Almost forgot to "rest" the clock in my GPS !!

>
>Any GPS unit I've ever used set itself... I don't even think you could set
>it to a different time if you wanted to...


You can set the time zone, you can also enable or disable summer time.
Not all GPS receivers know when your local standard and summer time
changes, even if they do they do not know if you require them to change.

--
Ian G8ILZ
 
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MarkČ
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      10-30-2006
Prometheus wrote:
> In article <JFa1h.64$(E-Mail Removed)>, MarkČ
> <mjmorgan@cox.?.net.invalid> writes
>> Mike Fields wrote:
>>> "Ray Fischer" <(E-Mail Removed)> wrote in message
>>> news:4544f26a$0$34491$(E-Mail Removed)...
>>>> Ed Ruf (REPLY to E-MAIL IN SIG!) <(E-Mail Removed)> wrote:
>>>>> That time of year for many of us again.
>>>>
>>>> ... when clocks get really tired and need to be "rested" for an
>>>> hour.
>>>
>>> Of course there was that scene from the movie "Animal House"
>>> (for those old enough to remember it) where they were staging
>>> a raid and synchronizing their watches -- they were all at 11:00
>>> or some such "exactly" except for John who was at 3:17 or some
>>> such time .. OK, good to go !!
>>>
>>> Almost forgot to "rest" the clock in my GPS !!

>>
>> Any GPS unit I've ever used set itself... I don't even think you
>> could set it to a different time if you wanted to...

>
> You can set the time zone, you can also enable or disable summer time.
> Not all GPS receivers know when your local standard and summer time
> changes, even if they do they do not know if you require them to
> change.


Ya, I think you're right, and I think what I'm remembering is the lack of
ability to set minutes, etc.
The hours were set in relationship to GM time, and you could only select
your time in relation to that.


--
Images (Plus Snaps & Grabs) by MarkČ at:
www.pbase.com/markuson


 
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Mike Fields
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      10-30-2006

"John McWilliams" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed). ..
> Mike Fields wrote:
>>
>> Almost forgot to "rest" the clock in my GPS !!

>
> That's frightening. The having a GPS that needs to have its time set
> manually, that is.
>
> What make and model?
>
> --
> john mcwilliams


Actually, when I went to set it, it was smarter than that.
It simply asked me to confirm Standard Time when I
turned it on. Magellan Meridian Gold -- now if they
would only put the map info in there so it could set itself
to the correct local time zone as you move around
(unless you are using UTC that is).

mikey

 
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Dave Martindale
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      10-31-2006
(E-Mail Removed) writes:

>> Almost forgot to "rest" the clock in my GPS !!


>That's frightening. The having a GPS that needs to have its time set
>manually, that is.


Many GPS receivers need to be told the offset between local time and UTC
(GMT). That offset changes at the beginning and end of Daylight Savings
Time.

Now, some GPS receivers know the DST algorithm used in the USA and
Canada, and if you happen to live in one of those places, you can get
your GPS to update the offset automatically. But that doesn't apply to
most of the world.

Dave
 
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Holley
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      10-31-2006

"Dave Martindale" <(E-Mail Removed)> wrote in message
news:ei6q0s$mr$(E-Mail Removed)...
> (E-Mail Removed) writes:
>
>>> Almost forgot to "rest" the clock in my GPS !!

>
>>That's frightening. The having a GPS that needs to have its time set
>>manually, that is.

>
> Many GPS receivers need to be told the offset between local time and UTC
> (GMT). That offset changes at the beginning and end of Daylight Savings
> Time.
>
> Now, some GPS receivers know the DST algorithm used in the USA and
> Canada, and if you happen to live in one of those places, you can get
> your GPS to update the offset automatically. But that doesn't apply to
> most of the world.
>
> Dave


And those in the US that do will be needing an update for that algorithm
when the dates for DST change next year...

Holley


 
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Dave Martindale
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      10-31-2006
"Holley" <(E-Mail Removed)> writes:

>And those in the US that do will be needing an update for that algorithm
>when the dates for DST change next year...


Which is only likely to happen for GPS receivers that (a) have the
firmware in flash RAM and (b) were built by manufacturers that issue
firmware updates and (c) are recent enough to still be supported by the
manufacturer.

The rest of them will just revert to manually changing the DST offset in
the spring and the fall on the appropriate date. Which reminds me, I
haven't reset my own GPS receivers yet...

Dave
 
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John McWilliams
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      10-31-2006
Dave Martindale wrote:
> "Holley" <(E-Mail Removed)> writes:
>
>> And those in the US that do will be needing an update for that algorithm
>> when the dates for DST change next year...

>
> Which is only likely to happen for GPS receivers that (a) have the
> firmware in flash RAM and (b) were built by manufacturers that issue
> firmware updates and (c) are recent enough to still be supported by the
> manufacturer.
>
> The rest of them will just revert to manually changing the DST offset in
> the spring and the fall on the appropriate date. Which reminds me, I
> haven't reset my own GPS receivers yet...


Nor have I. But, since I really don't need it to display proper local
time, I may not.

My original t.i.c. point was that if the GPS didn't know what time it
was, down to a very tiny tick, it'd be useless.


--
John McWilliams
 
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Dave Martindale
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      11-01-2006
(E-Mail Removed) writes:

>Nor have I. But, since I really don't need it to display proper local
>time, I may not.


Just leave it set to UTC all the time? That does make sense. I never
look at a GPS receiver to determine the time; I use a watch for that.
Sometimes I use the GPSr to set the watch, but then I only care about
the seconds and maybe the minutes.

>My original t.i.c. point was that if the GPS didn't know what time it
>was, down to a very tiny tick, it'd be useless.


Well, yes and no. The entire GPS system is normally closely
synchronized with USNO time, so it can be used to determine what time it
is now, as well as measure the passage of time and calculate location.

But suppose instead that a gremlin got into the GPS system and it was
some unknown amount of time offset from USNO. Without some independent
way to measure and remove this offset, the system would become useless
for measuring the current time.

But as long as the whole system was synchronized to the same wrong
clock, navigation would still work perfectly well, since that's done
entirely with time differences. And as long as the wrong clock was
running at the correct rate, the GPS system would be just as good at
measuring the passage of time or frequency.

One of the neat things about GPS is that it calculates positions based on
time difference measurements with a precision of a few ns, even though
the local oscillator need not be better than a cheap crystal. The local
clock error disappears in the calculations.

Dave
 
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