Reference Tool; Figure 3-7 Sample Calibrator - Northern Digital Polaris Vicra User Manual

How the Polaris Vicra System Works
Pivoting
You can also determine the tool tip offset using a process called pivoting, using either NDI ToolBox
or NDI 6D Architect software. During the pivoting procedure, the Polaris Vicra System will
measure the positions of the markers while you pivot the tool. The software collects this data, and
uses it to determine the tool tip offset. Instructions on how to pivot a tool are detailed in
"Determining the Tool Tip Offset" on page
6D Architect User Guide" and online help, and in the NDI ToolBox online help.
3.9

Reference Tool

A reference tool is a tool whose local coordinate system is used as the global coordinate system in
which other tools are tracked. The Polaris Vicra System tracks all the tools, including the reference
tool, and reports the transformations in the coordinate system of the Position Sensor (described on
page 26). Software (such as NDI ToolBox) then calculates and reports the positions and orientations
of all other tools with respect to the position and orientation of the reference tool.
Note
Use a reference tool to ensure minimal drift in the measurements produced; specifically, drift caused by time,
settling and/or temperature.
It is the application software, not the Polaris Vicra System, that calculates the tool transformations with respect
to the reference tool.
For example, in neurosurgery the reference tool can be attached to the patient's head. Then a
registration procedure is performed that defines the reference tool's position relative to the patient's
head. From then on, if either the patient's head or the Position Sensor shifts, the measurements are
36
Probe
Calibrator

Figure 3-7 Sample Calibrator

Clamp Probe in Place
Place Tool Tip at Origin
of Calibrator
45. In addition the procedure is also detailed in the "NDI
Polaris Vicra User Guide - Revision 2