Abstract Biostereometrics is an accurate anthropometric system for quantifying geometric changes of facial form and the relationship of features as they are influenced by growth and by surgery. Facial features distant from the site of surgical intervention are influenced in their geometric relationship to each other by changes in the soft-tissue drape brought about by manipulation of skeletal tissues. The most accurate coordinate system should be elsewhere than on the surface of the face, but if this is not possible it should be in an area farthest removed from the surgical site. This investigation demonstrates that a usable coordinate transformation system can be created by connecting points supernasale and subnasale for establishing the Y Z plane and the construction of the X Z plane at subnasale. Accurate comparative numerical measurements can be made by using soft-tissue landmarks.