Re: deviceorientation calibration

> I think its unclear in particular for beta and gamma values that to not tend
> to have a continuous gradation in 360 degree space.
I'm not sure what you mean by this. Why are beta and gamma not continuous?

> Based on the provided photo the device is in a [0, 0, 0] position based on
> the xyz system included in the spec. The fact that both z (beta) and x
> (gamma) values are zero is inferred from the fact that the device is resting
> on a (presumably level) table top. In reality the only important component
> is that y (alpha) is oriented towards the north (as determined by an
> independent compass).
OK, it sounds like you mean that the body's y axis is in a horizontal
plane and pointing north. In this case, alpha is zero.

> It's a simple rotation so that, as we rotate the device towards us, we are
> able to observe changes to the gamma reading (rather than a beta reading if
> the device was not rotated 90 degrees as per the beta reference plane
> described).
You don't need to apply this initial rotation (alpha = -90 degrees) in
order to vary gamma. Gamma is rotation about the body's y axis (the
long axis of the device pictured) and can be applied irrespective of
the value of alpha (or beta).

> Each user agent has implemented this differently which hints that we could
> provide more information in this regard.
Agreed.

> I still think we should go further to include radar charts describing the rotation in each of three reference
> planes for alpha, beta and gamma.
I'm not sure a radar chart is appropriate. They're intended to
simultaneously display multiple variables, with each variable
presented on a separate axis of the chart. For your 'reference
planes', there is only one variable (alpha, beta or gamma) being
varied in each case.

Received on Monday, 25 June 2012 13:24:50 UTC