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Author Topic: Sat-Nav Speed Read Out.  (Read 934 times)

sevenlayermuddle

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Re: Sat-Nav Speed Read Out.
« Reply #15 on: October 25, 2017, 01:45:53 PM »

@ sevenlayermuddle
I don't have the hours available to study the subject in depth, but reading around various sites, I get the impression that Doppler was the predominant method used by earlier systems such as the US Navy's Transit (NAVSAT), whereas the current GPS system uses it in an auxiliary correction/confirmation way - for want of a better phrase.

See also this link, which seems to favour the Doppler argument, quoting from an actual Navstar documentation source.  It also mentions accuracy of 0.1 to 0.5 mph is typical of what you can count on in automobile applications.  I suspect that is better accuracy than can be expected from a mechanically coupled wheel speed sensor, due to changes in tyre circumference as the tread wears down, among other variables.

http://gpsinformation.net/main/gpsspeed.htm

But I did acknowledge that opinions differ, and it is clear (and annoying!) that facts are scarce.  I have seen the Doppler option argued out countless times, and never a clear winner, never a truly authoritative source.     :)
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