Within each series, Xsens offers several product variants. Each variant is based on a firmware version which enables different functionalities. The figure below summarizes the functionality of each variant.
From IMU to GNSS/INS
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).
The Vertical Reference Unit (VRU), also referred to as Active Heading Tracker (AHT) 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/AHT 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 Additional setting options and features).
This is the full Attitude and Heading Reference System (AHRS). It provides various outputs: roll, pitch and heading (magnetic referenced yaw). In addition, all functionalities of the IMU and VRU are also available in this product variant.
The GNSS/INS variant is a product with an interface to an external or internal (RTK) 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/AHT and AHRS are also available in this product variant.