Analysis of body surfaces in a body-fixed coordinate system

Visualisation of shape and shape change e.g. by contour lines depends on the selection of the coordinate system of the contour levels. This is elucidated by using the plaster cast of a scoliotic back being rotated in front of a 3-D measurement and analysis system. Axial rotation through an axis parallel to the contour planes results in a dramatic change of the contour patterns on the back. This is in contrast to the expectation of the ingenuous viewer interpreting the contour line pattern like a fingerprint. To meet this attitude shape analysis must be referenced to a body fixed coordinate system, which may be defined by anatomical landmarks. It is shown, that vertebra prominens and the lumbar dimples provide anatomical landmarks capable for this purpose.