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Re: Sensor API feedback: OrientationData

From: SULLIVAN, BRYAN L <bs3131@att.com>
Date: Fri, 9 Mar 2012 22:26:46 +0000
To: "jmcf@tid.es" <jmcf@tid.es>, "doug.turner@gmail.com" <doug.turner@gmail.com>, "public-device-apis@w3.org" <public-device-apis@w3.org>
Message-ID: <659kfyfwk7ed8a0lmxj7ubw9.1331331666963@email.android.com>

I agree with Jose, these types of optimizations are necessary in the API. An API which does not perform some reasonable signal integration (or enable the app to specify the event rate /conditions) will be ineffective.




-------- Original message --------
Subject: Re: Sensor API feedback: OrientationData
From: JOSE MANUEL CANTERA FONSECA <jmcf@tid.es>
To: Doug Turner <doug.turner@gmail.com>,"public-device-apis@w3.org" <public-device-apis@w3.org>
CC: Re: Sensor API feedback: OrientationData


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 22:27:52 UTC

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