Part of you answer can be found here
https://surfer.nmr.mgh.harvard.edu/fswiki/CoordinateSystems

tkregister2 and the .dat file format are obsolete, use tkregisterfv. This is just a front-end for FreeView; it always uses LTA.

I'm not sure if there is documentation for the LTA format. The first 4x4 matrix is the transform that goes from the source (src) to the target (dst). The vox2ras matrix for each is in the file (see the Coord systems docs above). The intrepretation of the transform matrix depends on the type (eg, VOX_TO_VOX or RAS_TO_RAS)

On 3/25/2020 5:00 PM, Xiaojiang Yang wrote:

External Email - Use Caution

Hi everyone,

I am confused by the two types of registration files: .lta and .dat.

.dat file is simpler and easier to understand. But for the .lta files, there seems to be no detailed explanation regarding it. Can anyone point out to me where can I find the detail explanation of the file? And, what's the relationship between .lta and .dat file?

Also, .lta files seem to cause some compatibility issues. For example, if I use the tkregister2 utility to make some changes to the registration file of type .lta (generated by bbregister), like below

tkregister2 --mov $someSeries --reg $SUBJECTS_DIR/$subjectid/mri/transforms/FLAIR.auto.lta --surf pial

and save it from the GUI, then many errors occur in the console window, like below:

......

MatrixAsciiReadFrom: could not scanf parms
ERROR: TransformLTA2RegDat(): type = 2011264000, must be 1 or 0 or 14
Segmentation fault (core dumped)

Actually that is because the registration file has been saved in the format of .dat, although the file extension is still .lta, and the tkregister2 program finally cracks when reading the newly saved .lta file.

Anyone can solve my confusion? Thank you!
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