AB- V-MA-00650
01 February 2021
JF/RR
4
LD900 and INS
Commissioning Guide
Reference Frames
It is important to have a basic understanding of reference frames when dealing with INS. Reference frames are
especially important when configuring the systems rotational offsets. Two types of reference frames will be
considered, the Vessel Reference Frame and the IMU Body Frame.
Vessel Reference Frame
The definition of the Vessel Frame is as follows:
X-axis
– points out the starboard side of the vessel
Y-axis
– points out the front of the vessel in the direction of travel
Z-axis
– points up vertically on the vessel
Vessel Reference Frame
IMU Body Frame
The definition of the IMU Body frame is given by the physical axes of the IMU and represents how the sensors
are mounted inside the IMU. Both the IMU Body frame axes and Centre of Navigation markers are on two of
the IMU enclosure sides
The Centre of Navigation markers highlight the centre of the Rotational axes of the IMU, the actual centre of
navigation lies internally in the IMU where the XYZ rotational axes intersect. Therefore, If the user measures all
translational offsets to a single Centre of Navigation
marker
then two of the translational offsets must be
adjusted to be aligned with the Centre of Navigation. The figure below illustrates the position of the Centre of
Navigation markers and the dimensions in millimetres.
IMU-ISA-100C Centre of Navigation Markers
