Hi pt,
Sorry that I have another question about this.
Calculating the distance is just one analysis we're doing. Another analysis we're trying to do, and this might actually requires a flat map:
We want to put the interested voxels within a cluster into a flat map and average the feature values through different axis that go through the center of the cluster.
I think this could only be done on a flat map. If this is the case, do you have any suggestions on the error I encountered at the beginning?