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RE: [geolocation] accuracy attribute

From: Mandyam, Giridhar <mandyam@qti.qualcomm.com>
Date: Fri, 18 Sep 2015 15:49:45 +0000
To: "public-geolocation@w3.org" <public-geolocation@w3.org>
Message-ID: <4c414c92c59c464f8edf3e581e70ccd9@NASANEXM01C.na.qualcomm.com>
I did not participate in the early days of development of the geoloc. API - I did however participate at the time in the development of the old BONDI specification and looked into what platforms were offering at that time (2007 - 2008).  A popular API at that time was the JavaME JSR-179 specification, which defined accuracy as a radius (meters) with 1-sigma confidence.

It looks like it was a prescient decision to make the confidence level a "should" requirement.  For instance, Android LocationManager seems to only require 68% confidence level:  see http://developer.android.com/reference/android/location/Location.html#getAccuracy%28%29.

My conclusion is that your interpretation is correct, with the caveat that the confidence level of 95% may not be met by a given implementation.

Corrections/modifications/comments welcome, of course.

-Giri

-----Original Message-----
From: Tobie Langel [mailto:tobie@sensors.codespeaks.com] 
Sent: Friday, September 18, 2015 8:31 AM
To: public-geolocation@w3.org
Subject: [geolocation] accuracy attribute

Hi,

Looking at the accuracy attribute[1] in the Geolocation spec which
reads:

"The accuracy attribute denotes the accuracy level of the latitude and longitude coordinates and is specified in meters. [...] The accuracy and altitudeAccuracy values returned by an implementation should correspond to a 95% confidence level."

I assume this means that the user agent is actually positioned within a circle with radius equal to the accuracy in meters. Is this a correct interpretation?

Thanks,

--tobie

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[1]: http://dev.w3.org/geo/api/spec-source-v2.html#accuracy
Received on Friday, 18 September 2015 15:50:15 UTC

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