When figuring that a horse is 2 wide, or 3 wide, what is the distance between horses (center to center) that is used?

In looking at videos, it looks like a horse that is 2 wide is about 4 feet, center to center, from the horse on the rail, and that a horse that is 3 wide is about 8 feet, center to center, from the rail horse, etc.

Any info on this would be appreciated.

Thank you.

TGAB: Determining what path a horse runs in is done by visual observation.

BitPlayer: Since you equate being one path wider around a turn with one length of ground loss, your assumption must be that the center-to-center distance between paths is the length of a horse divided by 3.14 (pi).  On that basis, 4 feet sounds pretty close.