Let's first review what kind of mobile phone sensors there are and what they report. Most smart devices are now equipped with several built-in sensors that measure the motion, position, orientation, and conditions of the ambient environment. As sensors provide measurements with high precision, frequency, and accuracy, it is possible to reconstruct complex user motions, gestures, and movements. Sensors are often incorporated in various applications; for example, gyroscope readings are used to steer an object in a game, GPS data is used to locate the user, and accelerometer data is used to infer the activity that the user is performing, for example, cycling, running, or walking.
The following diagram shows a couple of examples of what kinds of interactions the sensors are able to detect:
Mobile phone sensors can be classified into the following three broad categories:
- Motion sensors: This sensor measures acceleration and rotational forces along the three perpendicular axes. Examples of sensors in this category include accelerometers, gravity sensors, and gyroscopes.
- Environmental sensors: This sensor measures a variety of environmental parameters, such as illumination, air temperature, pressure, and humidity. This category includes barometers, photometers, and thermometers.
- Position sensors: This sensor measure the physical position of a device. This category includes orientation sensors and magnetometers.
- Android sensors framework: http://developer.android.com/guide/topics/sensors/sensors_overview.html
- iOS Core Motion framework: https://developer.apple.com/library/ios/documentation/CoreMotion/Reference/CoreMotion_Reference/
- Windows phone: https://msdn.microsoft.com/en-us/library/windows/apps/hh202968(v=vs.105).aspx
In this chapter, we will work only with Android's sensors framework.