Clock Differences?

[+revnine]

I have been comparing my GPS V and a new Meridian Platinum for the last week or so. As far as accuracy goes, both seem to be very good. There are good features with both units (but that's another post). With WAAS off on both units, I get very little (if any) difference in static coordinates with the units side-by-side (+/- .001 seconds). While I was comparing coordinates, I noticed that the clock on the Platinum was a few (2-3) seconds behind the clock on the GPS V....which got me wondering. Aren't the internal clocks set off of the sats they are receiving and shouldn't the times be the same assuming they were locked on the same set of sats? Thanks in advance!

 

Tony

[+Jamie Z]

Hmmm, curious.

 

I would think that the clocks should be nearly identical. Of course, I don't know any technical details.

 

Jamie

[+apersson850]

Internally in each unit, the clocks are identical to a few nanoseconds. However, the process running in the unit, that's responsible for updating the clock display, may not have the same priority in each unit.

 

So, even if they both know the time very well, one of them may be less eager to tell you about it, and hence drag behind a little.

 

Anders

[+st_richardson]

quote:

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Originally posted by Anders:

 

So, even if they both know the time very well, one of them may be less eager to tell you about it, and hence drag behind a little.

http://img.Groundspeak.com/user/avatar/24148_200.jpg

 

Anders

---

 

That's funny.

 

Someone once said "A person with one GPS knows where he is. A person two GPS units doesn't."

 

Can we now rephrase that to read "A person with one GPS knows what time it is. A person two GPS units doesn't."?

[+apersson850]

If you read one post to this forum, you know the answer. If you read more posts, you aren't certain any longer.

 

Maybe we should issue a recommendation: If you own more than one GPS, don't turn them on at the same time.

 

 

Anders

[+phantom4099]

I posted a similar occurance back in november. My meridian was 2-3 seconds behind my 315.

 

Wyatt W.

 

The probability of someone watching you is directly proportional to the stupidity of your actions.

[Best_Buddies]

That's OK, because supposedly the GPS time is off by 13 seconds from the real time in any case (unless the GPS firmware accounts for this 13 seconds).

 

-----

Any similarity between my opinions and reality is entirely coincidental.

--Harrkev

[jfitzpat]

FWIW, I think that this is a small Meridian display issue. We just lined up an eTrex yellow, a Legend, a Vista, a GPS315, a GPS320, and a map 330x and the times were essentially the same.

 

The Meridian green is about 3 seconds behind.

 

-jjf

[Kerry.]

quote:

---

Originally posted by harrkev:

That's OK, because supposedly the GPS time is off by 13 seconds from the real time in any case (unless the GPS firmware accounts for this 13 seconds).

---

 

Not only supposedly but fact, for the moment anyway until the next leap second adjustment is made (when ever that might be decided?)

 

GPS time has not changed since the system was born on the 5/6 Jan 1980 as the world is slowing down but all is taken care of in the Nav message to correct for "our" time.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

quote:

---

Originally posted by harrkev:

That's OK, because supposedly the GPS time is off by 13 seconds from the real time in any case (unless the GPS firmware accounts for this 13 seconds).

---

 

Not only supposedly but fact, for the moment anyway until the next leap second adjustment is made (when ever that might be decided?)

 

GPS time has not changed since the system was born on the 5/6 Jan 1980 as the world is slowing down but all is taken care of in the Nav message to correct for "our" time.

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go