User Manual

0 0 1

0 1 0

1 0 0













Here O represents the object coordinate system and S the standard sensor coordinate

system described in Section 11.6.2. Once the object alignment matrix is set to R

, the sensor

output will be expressed with respect to the object coordinate system shown in figure (b),

below.

11.6.4 Heading Reset

It is often important that the global Z-axis remains along the vertical (defined by local gravity

vector), but the global X-axis has to be in another direction. In this case a heading reset may

be used, this is also known as “bore sighting”. When performing a heading reset, the new

global reference frame is chosen such that the global X-axis points in the direction of the

sensor while keeping the global Z-axis vertical (along gravity, pointing upwards). In other

words: The new global frame has the Z axis along gravity, pointing upwards, the X-axis in the

plane spanned by the vertical and the sensor X-axis, perpendicular to the global Z-axis and

the Y-axis such that a right handed coordinate system is formed.

NOTE: After a heading reset, the yaw may not be exactly zero, this occurs especially when

the X-axis is close to the vertical. This is caused by the definition of the yaw when using Euler

angles, which becomes unstable when the pitch approaches ± 90 deg.

11.6.5 Object Reset

The object reset function aims to facilitate in aligning the MT coordinate frame (S) with the

coordinate frame of the object to which the MT is attached (O). After an object reset, the S

coordinate frame is changed to S’ as follows:

 the S’ Z-axis is the vertical (up) at time of reset.