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Document MT1600P.2019.A
© Xsens Technologies B.V.
MTi Family Reference Manual
2.1 From IMU to GNSS/INS
Within each MTi series, Xsens offers several product variants. Each variant is based on a firmware
version which enables different functionalities. Figure 1 summarizes the functionality of each variant.
Figure 1: From IMU to GNSS/INS
2.1.1 IMU
The IMU variant is an Inertial Measurement Unit that measures 3D acceleration and 3D rate of turn with
the addition of 3D magnetic field data and, depending on the product, barometric pressure. It does not
fuse sensor data to deliver orientation estimates. The IMU can also be configured to output data
generated by the strapdown integration algorithm (orientation increments
∆
q and velocity increments
∆
v).
2.1.2 VRU
The Vertical Reference Unit (VRU) adds the first layer of algorithms which uses gravity as a reference
for roll and pitch calculations. Essentially it delivers the same data as the AHRS, except for the yaw.
The yaw estimate of a VRU product is unreferenced, which means that it is computed without any
geographic/magnetic reference, though still superior to just gyroscope integration (e.g., when using the
gyro bias estimation techniques). All data outputs from the IMU are also available in this product version.
The AHS feature is also available in this product variant (see also chapter 4.4.7)
2.1.3 AHRS
This is the full Attitude and Heading Reference System (AHRS). It gives various outputs: roll, pitch and
heading (true magnetic North referenced yaw). In addition, all functionality of the IMU and VRU are also
available in this product variant.
2.1.4 GNSS/INS
The GNSS/INS variant is a product with an interface to an external or internal GNSS receiver as well as
a barometer. It provides roll, pitch, yaw/heading, as well as 3D position, 3D velocity and time data. In
addition, all data outputs of the IMU, VRU and AHRS are also available in this product variant.
