7
5. REFERENCE SYSTEM
All raw inertial measurements (
linear accelerations
,
angular velocity
and
earth
magnetic field
provided by the unit are referred to the reference system shown below (
body frame
).
The orientation of the unit in the space is referred to an earth-bound frame where:
X
is pointing
NORTH
Y
is pointing
WEST
Z
is pointing
UPWARDS
The orientation of the sensor is given by a
quaternion
(
q0,q1,q2,q3
) representing the
rotation
of the
unit
’s
body frame
with respect to the
earth frame
.
Thus when the X axis of the sensor is pointing NORTH and Y axis is pointing WEST the output is the
Identity Quaternion
(1,0,0,0).