IMU

I was looking for an easy way to access an IMU for some quick tests. I settled on a smartphone sensor because all the sensor fusion / calibration software is built in. Furthermore, the device motion and device orientation events available in the Web API make it easy to grab the data, send it to a computer through websockets and then pipe it into any application.

Device Orientation: {% highlight javascript %} window.addEventListener(“deviceorientation”, function(event) { console.log( event.absolute, // Boolean whether or not the data is “absolute” // Absolute data means that if your phone is // flat on a surface, pointing north, all three // readings should be 0. event.alpha, // Yaw event.beta, // Pitch event.gamma // Roll ); }); {% endhighlight %}

These numbers are all in degrees. A sample is available on this site or on codepen. It may take a bit of time for the orientation to calibrate itself.

Additionally, there is also the device motion event, which can get the accelerometer and gyroscope data.

Device Motion: {% highlight javascript %} window.addEventListener(“devicemotion”, function(event) { console.log( event.acceleration, // object containing {x, y, z} fields event.accelerationIncludingGravity, event.rotationRate, // object containing {alpha, beta, gamma} fields event.interval // dt ); }); {% endhighlight %}

Rotation rate might not be useful for orientation given the orientation data already available, but acceleration can filtered and then used for positioning.