[IGSTK-Developers] calibration (followup to David and James's discussion)

[Ziv Yaniv]

Hi David and James,

   Following your discussion from yesterday I just wanted to comment on 
the use of pivot calibration.
   Pivot calibration only gives the translation between the tool tip and 
the tracked coordinate system .
   The way James uses it to get the orientation of the tool relies on 
the following assumptions:
   1.we have a cylindrical tool (pointer, needle, etc.).
   2. the origin of the tracked coordinate system is on the axis of the 
cylinder.

   This is the case for all the electromagnetic tools we have (needles, 
catheters).
    This approach will not work for many cylindrical tools, as we are 
not guaranteed
     that the origin of the tracked coordinate system  is on the axis of 
the cylinder.
    I do not know of generic calibration routines that will give the 5 
degrees of freedom for pointer like tools without any
    assumptions or specific hardware (in my old lab we used a Traxtal 
calibration jig with the math tailored to it).

    As IGSTK aims for a wide audience I believe pivot calibration to get 
the translation is sufficient.
    Users that want the additional  orientation information will have to 
write their custom code that fits
    their specific setup (calibration jig, assumptions 1+2 are valid, etc.).

                                                    Ziv