User Manual

© Xsens Technologies B.V.
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11.6 Coordinate Systems
11.6.1 Calibrated Sensor Readings
All calibrated sensor readings (accelerations, angular velocity, earth magnetic field, pressure)
are in the right handed Cartesian co-ordinate system as defined in the figure below. This co-
ordinate system is body-fixed to the device and is defined as the sensor co-ordinate system
(S). The 3D orientation output is discussed in Section 11.6.2.
The co-ordinate system is aligned to the external housing of the MTw.
High accuracy alignment between the (plastic) housing and the sensor-fixed output
coordinate system (S) is not possible for the MTw for obvious reasons. The actual alignment
between the S co-ordinate system and the bottom part of the plastic housing is guaranteed
to <3
o
.
The non-orthogonality between the axes of the body-fixed co-ordinate system, S, is <0.1
o
.
This also means that the output of 3D linear acceleration, 3D angular velocity (gyro) and 3D
magnetic field data all will have orthogonal XYZ readings within <0.1
o
.
11.6.2 Orientation Coordinate System
The MTw calculates the orientation between the sensor-fixed co-ordinate system, S, and a
earth-fixed reference co-ordinate system, G. By default, the local earth-fixed reference co-
ordinate system used is defined as a right handed Cartesian co-ordinate system with:
 X positive when pointing to the local magnetic North.
 Y according to right handed co-ordinates (West).
 Z positive when pointing up.
The 3D orientation output (independent of output mode, see Section 11.7) is defined as the
orientation between the body-fixed co-ordinate system, S, and the earth-fixed co-ordinate
system, G, using the earth-fixed co-ordinate system, G, as the reference co-ordinate system.
Z
Y
X