[Lazarus] Portable way to get accurate timestamps?

[John]

On 24/02/2011 5:32 AM, Bo Berglund wrote:
> On Wed, 23 Feb 2011 10:20:19 +0100, Sven Barth
> <pascaldragon at googlemail.com>  wrote:
<snip>
> Yeah, but my efforts are not successful in using a USB connected GPS
> sensor and trying to get accuracy from the telegrams sent by it. I
> think much of the time wobble I see is caused by USB latency in the
> track from the GPS sensor to the USB hub to the next USB hub and then
> into the laptop.
> Add to this the way the device driover (Prolific USB2Serial) might
> buffer up the data before it reaches the Windows serial system and
> there are lots of places time can be lost.
>
> As I posted just a minute ago I found the perfect solution in a Garmin
> device with microsecond accurate pulse output.
>
> Have just ordered one for testing.
>
In any case, most GPS engines have a certain latency in even sending out 
the serial time signals, and, as I understand it, don't consider the 
time as important as the position in the internal program, in terms of 
what they output.  The internal time, is of course, critical.  So if you 
are interested in anything like millisecond  timing, the 1 PPS signal 
(as in other post) is definitely the way to go.  This is used regularly 
by amateur (and quite possibly professional) astronomers for timing 
stuff, eg to get exact times of a video stream on a frame by frame 
basis.  If you can't find enough information from your existing 
sources,  try a search on "occultation timing".

cheers,
John Sunderland