All axes are described relative to the IMU person image on the sensor: the ‘feet’ close to the bottom edge, with the data transfer pins, and the ‘top’ of the sensor the edge opposite the data transfer pins. ‘Left’ and ‘right’ are relative to the IMU person.
+X axis – superior to the IMU person, a vector running from the base of the sensor through the top of the sensor
+Y axis – to the right of the IMU person, a vector running from the left edge of the sensor through the right edge
+Z axis – coming out of the sensor towards you when looking at the IMU person, a vector running from the posterior aspect of the sensor through the anterior aspect