Qinertia uses the following geographical and mathematical conventions. If not specified otherwise, always consider that measurements are expressed using these conventions.
IMU Coordinate Frame
This frame defines the acceleration and rotations rate measurements and is, by definition the body coordinate frame. It is using a standard right hand rule X,Y,Z frame that is aligned to the NED frame when the unit is leveled and pointing north.
According to the "Right Hand Rule", rotations are positive clockwise in the axis direction:
Vehicle Coordinate Frame
Depending on application, a vehicle coordinate frame is defined as follows: X axis is turned in Forward direction, Z axis is turned Down, and Y axis, thanks to right hand rule is turned to the right of vehicle.
Ship Motion Conventions
The ship motion outputs are in a specific vessel coordinate frame:
Heave is the vertical position, with positive sign downwards
Surge is the longitudinal position, horizontal and turned toward the vessel bow
Sway is the transverse position; horizontal and turned in boat starboard
