Re: Date/Time accuracy (was Re: First TOM1 image under Rob's Software)

[Chris Albertson <chrisalbertson90278@yahoo.com>]

I think NTP is about 100 times more acurate then needed for TASS
but it's free and easy to set up.
At the level of resolution that us humans can notice "anything
works".  Noticing to less than 1/10th second is hard.

But if we are talking microseconds then even GPS has problems
because of the unpredictable propogation speed through the ionosphere.
The millitary grade GPS signal uses two frequencies so that the
differences in propogation speeds (which are frequency dependent)
tells the reciever enough about the real-time ionosphere that the
reciever can correct out the effects.  Effects are on the order
of a few meters over "C".

The bigger prolem with GPS, at the consummer level, is the update
rate of the LCD display and delay through the NMEA data port. 

WWV radio is in the HF frequency range and unless you live very close
to the transmitter comes to you after bounceing offone of the
ionoshpere layers.  The layers are not at constanthight so the path
lenght varies durring the day.   
> 


=====
Chris Albertson
  Home:   310-376-1029  chrisalbertson90278@yahoo.com
  Cell:   310-990-7550
  Office: 310-336-5189  Christopher.J.Albertson@aero.org
  KG6OMK


		
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