Subject: [Geopriv] Error distributions

From: Henning Schulzrinne <[email-masked]>
Date: Mon, 3 Mar 2008 16:17:37 -0500

Out of curiosity, a bit of googling found some examples of how error  
distributions are used:

http://www.its.bldrdoc.gov/isart/art05/slides05/feu_m/feu_m_slides.pdf

(slide 8)

By the way, that distribution is not Gaussian (one sigma seems to be  
44m, but then the 95%th percentile should be 88m, not 135 m).  
Certainly not uniform...

See also

http://www.gartrip.de/long.htm

I particularly like the bold part: "Do not rely on the "accuracy"  
indication of your receiver. An accuracy indication as low as 2 meters  
means only that the receiver believes it is so accurate. It does not  
mean that the position is really within 2 meters!"

Henning

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From: "Thomson, Martin" <[email-masked]>
Date: Mon, 3 Mar 2008 16:06:36 -0600

> mean that the position is really within 2 meters!"

This statement is interesting in light of the results on the page.
Either the author is dumbing it down, or he doesn't understand what the
2 metre value is indicating.  GPS errors are typically reported in terms
of a single standard deviation, which, on the horizontal, equates to
roughly 39% confidence.  As you can see from the plots on this page,
this is about right.

M
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