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East-North-Up (ENU) frame, meaning that Roll, Pitch and Yaw will equal 0 degrees when
the x-axis of the sensor is aligned with East, the y-axis with North and the z-axis upward:
•
X positive when pointing to the local magnetic East
•
Y positive when pointing to the local magnetic North
•
Z positive when pointing up
True North vs. Magnetic North
As defined above the output coordinate system of Xsens DOT is with respect to local
Magnetic North. The deviation between Magnetic North and True North (known as the
magnetic declination) varies depending on your location on earth and can be roughly
obtained from
various models of the earth’s magnetic field
as a function of latitude and
longitude.
4.1.3
Heading reset
Heading reset function allows user to align heading outputs among all sensors and with
the object they are connected to. Performing a heading reset will determine the orientation
and free acceleration data with respect to a different earth-fixed local frame (
L’
),
which
defines the L’ frame by setting the
X-
axis of L’ frame while maintaining the
Z-axis along
the vertical. It computes L’ such that Yaw
becomes 0 deg.
The heading reset function must be executed
during measurement and with
measurement mode including orientation output
. The reset orientation is maintained
between measurement start/stop and connection/disconnection but will be lost after a
device reboot.
The heading reset can be performed in Xsens DOT App and is available in SDK. Follow
these steps to do the heading reset in app:
1.
Put sensors in charger to give an aligned heading for all sensors; you can also
choose to place the charger flat on a surface so the Z-axis of sensors all pointing
upwards.
2.
Connect the sensors
3.
Start sensor fusion data measurement
4.
Press the button and select [Reset Heading]. It will apply to all the sensors under
measurement
5.
Choose [Revert Heading] if you want to undo the heading reset.
Figure 11: Heading reset/revert in Xsens DOT app
Refer to
Xsens DOT
SDK programming guide
for the implementation of heading reset
function with SDK.
