Question

While porting my Android app to iOS I was confused with one thing, so I want to find out: am I right or mo code works wrong. At Android device accelerometer returns values in physical measure units: m/s2. On ipad i get summary force approximately = 1.0 for still device(and i expect 9.8). My first explanation is that returning value is normalized to 9.8, so I must multiply it with 9.8 to get real force. My second idea – my code is totally wrong, but it’s hard to believe.

Answer 1

From the Docs on CMAcceleration:

CMAcceleration
The type of a structure containing 3-axis acceleration values.

typedef struct {
      double x;
      double y;
      double z;
} CMAcceleration;

X-axis acceleration in G’s (gravitational force).
Y-axis acceleration in G’s (gravitational force).
Z-axis acceleration in G’s (gravitational force).

A G is a unit of gravitation force equal to that exerted by the earth’s gravitational field (9.81 m s−2).