Accelerometry data including gravity can be retrieved both on Android and iOS phones:
- On iOS raw accelerometry data can be retrieved through
CMMotionManager. - On Android two different types of data including gravity can be retrieved through
SensorManager:TYPE_ACCELEROMETER: Acceleration force along the x/y/z axis (including gravity).TYPE_ACCELEROMETER_UNCALIBRATED: Measured acceleration along the X/Y/Z axis without any bias compensation.
An uncalibrated accelerometer sensor reports the acceleration of the device along the three sensor axes without any bias correction (factory bias and temperature compensation are applied to uncalibrated measurements), along with a bias estimate.
This begs the question: does iOS do any bias compensation on its CMMotionManager API? The CMDeviceMotion API documents that it removes gravity, but does not make explicit whether it does any additional calibration to remove potential sensor bias, similar to the Android API.
Retrieve data that has already been processed to remove environmental bias, such as the effects of gravity.
In other words, should iOS's CMMotionManager accelerometry be considered the equivalent of Android's TYPE_ACCELEROMETER_UNCALIBRATED or TYPE_ACCELEROMETER?
The text on the website you cited says: "The values reported by the accelerometers are measured in increments of the gravitational acceleration, with the value 1.0 representing an acceleration of 9.8 meters per second (per second) in the given direction." As I understand, this means that it is calibrated, making it the equivalent to TYPE_ACCELEROMETER.