Plus applications user manual  2.9.0.918b199
Software library for tracked ultrasound image acquisition, calibration, and processing.
Definition of commonly used coordinate systems

In Plus the following coordinate systems are used commonly:

Reference frame name Origin Unit Axes directions
Tracker Origin of the tracking system (position of the field generator, camera, etc.) mm as defined by the tracking system manufacturer
Stylus Origin of the marker that is attached to the pointer tool mm as defined by the tracking system / marker manufacturer
Probe Origin of the marker that is attached to the ultrasound probe (transducer) mm as defined by the tracking system / marker manufacturer
Reference Origin of the marker attached to the object of interest (phantom, cadaver, patient, etc.) mm as defined by the tracking system / marker manufacturer
StylusTip Tip of the stylus mm X axis: aligned with the Stylus coordinate system's X axis (unless StylusTip Z axis is parallel with the StylusTip Z axis - in this case the StylusTip Y axis is aligned with the Stylus X axis).
Y axis: chosen to be the cross product of the Z and X axes.
Z axis: the axis that points from the Stylus coordinate system origin towards StylusTip coordinate syste origin.
Image Position of the pixel that is in the origin of the MF oriented image pixel X axis: towards the marked side of the transducer
Y axis: towards the direction that points away (far) from the transducer
Z axis: cross product of X and Y
Transducer Center of the transducer crystal array mm X axis: towards the marked side of the transducer
Y axis: towards the direction that points away (far) from the transducer
Z axis: cross product of X and Y

Coordinate systems overview sketch (3D Slicer compatible interactive 3D model of the figure below is available here):

CoordinateSystemDefinitionsfCal.png