What is Gyroscope Sensors in Android, and How it is combined with Accelerometer Sensors ?

* Gyroscopes are very cool components that can measure the twist of a device about a reference
   frame.It measures the rate of rotation about an axis.

* When the device is not rotating,the sensor values will be zeroes and when there is rotation in
   any direction,you'll get non-zero values from the gyroscope.

* A gyroscope can't tell you everything you need to know, and unfortunately errors creep in over
   time with gyroscopes.But coupled with accelerometers,you can determine the path of movement
   of the device.

Combined with Accelerometer Sensor:

   Kalman filters can be used to link data from the two sensors together.Accelerometers are not
   terribly accurate in the short term,and gyroscope are not very accurate in the long term,so
   combined they can be reasonably accurate all the time.While Kalman filters are very complex,
   there is an alternative called Complementry filters that are easier to implement in code and
   produces results that are pretty good.

* The gyroscope sensor returns three values in the values array for the x,y and z axis.
  
* The units are radians per second,and the values represent the rate of rotation around each of
   those axis.

* One way to work with these values is to integrate them over time to calculate an angle change.
   This is a similar calculation to integrating linear speed over time to calculate distance.