Hi Don

By far the easiest way to do this is to find the locations of the points on the sphere then compute the length of the great circle arc connecting them, then correct by the ratio of the sqrt of the areas of the two surfaces.

Alternatively I think Rudolph may have had some tools for computing actual geodesics (the procedure about will give you like a 10% error)

Cheers

Bruce

From: freesurfer-bounces@nmr.mgh.harvard.edu <freesurfer-bounces@nmr.mgh.harvard.edu> On Behalf Of Krieger, Donald N.
Sent: Wednesday, July 21, 2021 10:53 AM
To: 'freesurfer@nmr.mgh.harvard.edu' <freesurfer@nmr.mgh.harvard.edu>
Subject: [Freesurfer] shortest distance between two points along the gray/white boundary

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Dear experts,

I would like to compute the shortest distance along the gray/white boundary between two points on the boundary, i.e. between points with “white” parcellation regions. The distance need not be guaranteed to be minimized and the path need not be unique. Can you suggest an approach using the freesurfer tools?

Thanks - Don

Department of Neurological Surgery

University of Pittsburgh