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Re: Sensor API feedback: OrientationData

From: Doug Turner <doug.turner@gmail.com>
Date: Fri, 9 Mar 2012 08:44:38 -0800
Cc: "public-device-apis@w3.org" <public-device-apis@w3.org>
Message-Id: <2A7D1739-4EED-4C37-8D2D-040B9FBE88F5@gmail.com>
To: JOSE MANUEL CANTERA FONSECA <jmcf@tid.es>
Jose,

Please see the geolocation (device orientation) mailing list for this specific issue and the WG response.

How do you know that the battery will be drained by the use case you mentioned? Did you measure this?

Thanks
Doug


On Mar 9, 2012, at 8:38 AM, JOSE MANUEL CANTERA FONSECA wrote:

> Hi Doug,
> 
> The problem with the Device Orientation Events spec is that there is no
> way for an application to specify how often the event should be raised by
> the UA. For instance Firefox Mobile implementation raises hundreds of
> events per second and when I implemented a Compass app I had to create a
> wrapper to filter out events to avoid collapsing the browser with
> thousands of repaints of the Compass canvas. But in the end battery can be
> drained due to this fact.
> 
> I totally agree that We should not confuse developers, and we should have
> only one mechanism but Device Orientation has flaws.
> 
> Thanks best
> 
> El 02/03/12 20:12, "Doug Turner" <doug.turner@gmail.com> escribió:
> 
>> Hi Jonas, Tran,
>> 
>> I am concerned that there is overlap between the Sensor Api and the
>> DeviceOrientaiton Spec:
>>  http://dev.w3.org/geo/api/spec-source-orientation.html
>> 
>> I worry that web developers will not know which API to use.  Tran, have
>> you looked at our draft specification?  I am wondering how we can make
>> these two efforts result in something that is consistent and pleasing to
>> developers.
>> 
>> 
>> 
>> Answer to questions Jonas raised:
>> 
>>> I'm having trouble understanding the difference between the
>>> OrientationData and AccelerationData sensors.
>> 
>> They are measuring different things.  Orientation has to do with rotation
>> about an axis measured by a gyro.  Acceleration will tell you change in
>> speed measured by an accelerometer.
>> 
>>> it's impossible to tell the difference between gravity and acceleration.
>> 
>> True. http://en.wikipedia.org/wiki/Equivalence_principle
>> 
>>> is the OrientationData sensor simply a convenience function on top of
>>> the AccelerationData sensor?
>> 
>> Both tell you something about the reference.  You really want to know
>> both acceleration and orientation to fully understand what is happening
>> to the reference.  You can't always determine orientation from
>> acceleration or visa versa.
>> 
>>> Could someone explain the meaning of the alpha, beta and gamma values?
>> 
>> The DeviceOrientation spec goes into great detail about what these values
>> are.
>> 
>> 
>> 
> 
> 
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Received on Friday, 9 March 2012 16:45:15 UTC

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