CODEWITHSUNDEEP
javascriptiosgyroscopedevice-orientation
BlackWolf
BlackWolf

Reputation: 5629

JavaScript deviceorientation on Microsoft Surface Pro 2: alpha and gamma values switched

I am using the deviceorientation event in JavaScript to retrieve Gyroscope data. So far, I have tested this on iOS devices which worked perfectly. Today I tried the same code on a Microsoft Surface Pro 2 tablet running Chrome 39 and noticed I get pretty strange values.

After exploring this a bit, it seems that the alpha and gamma values are switched on the Surface Pro, as it can be seen when testing on this page.

When lying flat on a table and rotating the device, my iPad Air changes its alpha value while the Surface Pro changes the gamma value. When picking up the device (so it stands at a 90 degree angle to the table), I get a gamma value of 90 on the iPad and an alpha value of 90 on the Surface Pro.

I suppose, according to the description given at HTML5Rocks about how those events should be working, the iPad is doing the correct thing but the Surface Pro is not.

So I guess my question is: Is this a known issue? Is there any way to detect or work around this?

WORKAROUND:

I am currently using the following workaround for this:

var alphaGammaFlipped = false;
window.addEventListener("deviceorientation", function(e) {
    if (e.alpha < 0 || e.gamma > 180) alphaGammaFlipped = true;

    var alpha = e.alpha;
    var beta  = e.beta;
    var gamma = e.gamma;
    if (alphaGammaFlipped) {
        var temp = alpha;
        alpha = gamma;
        gamma = temp;
    }

    // Do something with alpha, beta, gamma...
});

This code uses the assumption that alpha should be between 0 and 360 and gamma should be between -180 and 180. If one of them is out of bounds, this means that they are probably flipped. Obviously, this is just a workaround als also the values will be wrong as long as both stay between 0 and 180. If anyone has something better, I'd be glad.

Upvotes: 0

Views: 427

Answers (1)

Mr K
Mr K

Reputation: 48

In my case, with the same config (Surface Pro 2 + javascript deviceorientation), the three angles are reversed.

For fix this I do that :

false_alpha  =  gamma
false_beta   =  alpha
false_gamma  =  beta

(I noticed that there was no inversion with Internet Explorer 11 ...)

Upvotes: 0

Related Questions