W3C home > Mailing lists > Public > public-geolocation@w3.org > March 2012

Re: Comment on Device Orientation API

From: Wolfgang Damm <wolfgang.damm@wikitude.com>
Date: Thu, 1 Mar 2012 12:03:17 +0100
Message-ID: <CAAMsRONuiGbGkoX_tBewVVfj22qtDjxsf5mNY4JN4u6SAtNAHg@mail.gmail.com>
To: Lars Erik Bolstad <lbolstad@opera.com>
Cc: public-geolocation@w3.org, Martin Lechner <martin.lechner@wikitude.com>
Hi all,

my name is Wolfgang Damm and I'm working at Wikitude as Lead Software
Architect. In that role I'm responsible for developing an AR prototype
using the DeviceOrientation API. Let me jump right into the discussion.

Lars, thanks for adjusting the cap.

But, I still think that the specification needs to be reworded. The
pharse "significant change in orientation" is to vague and can be
interpreted in various ways. Even if it is problematic for our
usecase, Opera was still well within the specification.

A few usecase come to my mind (and I think you have thought of a few more
1. Augmented Reality
2. Games
3. Determining Screen orientation (only Up, Down, left, right is of

With the current specification I believe only usecase 3. is sufficiently
covered. For 1. and 2. it is up to the specific UA implementation if they
are possible.

In my opinion, to cover the different update rate/accuracy needs of
different usecases without draining battery or degrading performance the
optimal way would be to let the web app specify how many updates/what
accuracy it needs. But if this is not an option, there should be a more
concrete wording of when events should be fired. Something in the line of:

The event should be fired with a minimum update rate of around 100 ms or if
a significant change in orientation occurs. The definition of a significant
change in this context is left to the implementation.

By defining the update rate, a game developer knows what to expect when
using this API. It also helps in development that the event firing behavior
is more similar across different UAs.



2012/3/1 Lars Erik Bolstad <lbolstad@opera.com>

> Hi Martin,
> Sounds like we've capped this at a too high level in Opera's
> implementation. We'll adjust that.
> Lars Erik
> On 29.02.2012 21:40, Doug Turner wrote:
>> Hi Martin,
>> Thanks for your suggestion.  This is an interesting idea, and one
>> that was discussed.  The draft states:
>> The event should fire whenever a significant change in orientation
>> occurs. The definition of a significant change in this context is
>> left to the implementation. Implementations may also fire the event
>> if they have reason to believe that the page does not have
>> sufficiently fresh data.
>> I tend to think that Opera filtering at 4 degrees is a UA bug.  Maybe
>> a RFE.  I do not think I want to expose tighter control here to web
>> application.  Surely any change to the API allowing such control
>> could be veto'ed by the UA.  Opera could still cap their
>> notifications at 4 degree changes even though the web application
>> asked for something tighter.
>> It could also be an implementation concern.  I know when I fire lots
>> of events, the over all browser performance suffers.  I think UA's
>> need some flexibility here to provide the best possible performance.
>> Thanks again,
>> Doug Turner
>> On Feb 29, 2012, at 6:46 AM, Martin Lechner wrote:
>>  Dear members of the Geolocation Working Group,
>>> I am Martin Lechner, CTO of Wikitude, a member of W3C and developer
>>> of the Wikitude World Browser.
>>> We are currently developing an augmented reality project on
>>> platforms based on the DeviceOrientation API, and do have a comment
>>> regarding some specific items in the draft specification.
>>> The current specified update rate of the device orientation event
>>> is not sufficient for our usecase. Specifically the phrase: “the
>>> event should fire whenever a significant change in orientation
>>> occurs.” leaves it up to the implementation when exactly to fire an
>>> event.
>>> We are already seeing different implementation in the prerelease
>>> versions of Opera (LAB Opera Mobile) and Mozilla (Aurora). While
>>> Mozilla reports events quite frequently (which is preferred by us),
>>> Opera matches the specification and reports events only if there is
>>> a change of approximately 4 degrees.
>>> Our suggestion would be to let the web developer define how
>>> accurate the orientation changes should be reported. E.g. like the
>>> accuracy modes in Geolocation API. For AR it would be nice to have
>>> a high accuracy to achieve more events to get a smoother, more
>>> accurate calculation when moving the device.
>>> Best regards, Martin Lechner
>>> -- - - - Martin Lechner CTO
>>> Wikitude GmbH Ginzkeyplatz 11 5020 Salzburg/Austria Phone +43 662
>>> 243310 Mobile +43 676 840 856 300
>>> http://www.wikitude.com

Wolfgang Damm
Lead Software Architect

Wikitude GmbH
Ginzkeyplatz 11
5020 Salzburg/Austria
Email: wolfgang.damm@wikitude.com
Phone: +43 662 243310
Mobile: +43 676 840 856 900
Web: http://www.wikitude.com
Twitter: twitter.com/Wikitude
Facebook: facebook.com/wikitude

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Received on Friday, 2 March 2012 22:13:38 UTC

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