Document MT0605P.E
© Xsens Technologies B.V.
MTi User Manual
45
After an inclination and/or heading reset, the equation for
L’S’
R is applied (see above). It should be
noted that the inclination reset (
SS’
R) will not work if the sensor x-axis is aligned along the z-axis of the
object, since the sensor x-axis is used to describe the direction of the object x-axis. Furthermore, after
a heading reset, the yaw may not be exactly zero, especially when the x-axis is close to the vertical.
This is caused by the definition of yaw in Euler angles, which becomes unstable when the pitch
approaches 90 deg.
Figure 10: Top view and side view of an MT with coordinate frame S (left) strapped to an object and local
frame L. The different alignments and resets define the S’ and/or L’ frame. (a): the default orientation
output of S with respect to L: LSR; (b): after inclination reset, method
1: LS’R (c): after heading reset,
method 2: L’SR, (d): after alignment reset, method 3: L’S’R. All of these are also possible to set with
arbitrary alignments.
NWU and NED reference coordinate frames
The default reference coordinate frame in the MTi is ENU-frame, described in section 4.2.3, the MTi
supports two other reference coordinate systems that can be selected. These are NWU and NED.
NWU is the reference coordinate system that used to be the default up to the third generation MTi and
MTi-G. In order to configure the MTi to output in the NWU local frame, apply the following rotation
matrix in RotLocal.
RotLocal
𝑁𝑊𝑈
: [
0
1 0
−1 0 0
0
0 1
]