What exactly does "accuracy" mean in HTML5 geolocation?

Question

When using the HTML5 geolocation API I get, apart from latitude and longitude, also the "accuracy of the location in meters". What exactly does that mean (meters is not a unit of accuracy)?

I assume it shall be read as "with probability p the request was made within a meters of the returned location" - if so, what is p? Is it one standard deviation (p = 0.682?) Two standard deviations (p = 0.956?)

http://dev.w3.org/geo/api/spec-source.html isn't really explicit either.

Polynices

Answer 1

Quoting from the spec:

The accuracy and altitudeAccuracy values returned by an implementation should correspond to a 95% confidence level.

So, 95% confidence level it is. Then again, implementations can vary significantly in what they report...

Sayre

I guess it means that if we have an accuracy of R meters then any point in a circle of radius R meters centered in the referred point has a confidence level of 95%? My question is about R is the radius or the diameter of the circle? Also, its not clear to me if the confidence area shape is a circle or a rectangle. – Fireresistant