Computing head model: NAS, LPA, RPA, AC, PC, IH

Hello
Is there exact coordinates for NAS, LPA, RPA, AC, PC, IH to insert when computing head model? I am using default MRI.
Thanks

The position of the NAS/LPA/RPA points need to be set using the same anatomical convention in the MRI and in the MEG or EEG sensor referential.
http://neuroimage.usc.edu/brainstorm/Tutorials/ChannelFile#Automatic_registration

AC/PC/IH don’t need to be set precisely and can be estimated automatically when computing the transformation to the MNI space.
http://neuroimage.usc.edu/brainstorm/Tutorials/ImportAnatomy#MNI_transformation