AVR-Chat

On Jun 15, 2006, at 6:11 PM, John Samperi wrote:

> Interesting, for this time of application the error should not
> matter. So WHAT is GPS time? (I know Google is my friend) It just
> occurred to me that it may not be just a simple matter of reading
> the time off the receiver and displaying it. Say if the clock was
> located at the border of QLD and NSW (different time zones in Summer)
> would it give me QLD or NSW time? Is it that clever to differentiate
> the border line?

GPS keeps time in UTC. If the software in the GPS wishes to attempt  
adjustment for local time zones then that is up to the GPS's  
manufacturer.

The basic system sends pulses and markers always equally spaced. It  
happens due to leap seconds & the like there has been a slip between  
that and what humans consider the actual time. They don't slip the  
markers because the spacing between is critical for the navigation  
function. To resync the markers the entire GPS system would have to  
reboot.

There is a block of data being sent, slowly, that takes between 10  
and 15 minutes to complete. This block contains information such as  
updated satellite constellation as the GPS has to have accurate  
knowledge of where the satellites are located that it can compare the  
differences in arrival times of signals from each to know where  
itself is located. All kinds of things that are sure to change since  
the time of manufacture such as time slip adjustments.

--
David Kelly N4HHE, dkelly@HiWAAY.net
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Whom computers would destroy, they must first drive mad.