Subhash R. Lele & Joan T. Richtsmeier 
Invariant Approach to Statistical Analysis of Shapes [PDF ebook] 

Natural scientists perceive and classify organisms primarily on the basis of their appearance and structure- their form , defined as that characteristic remaining invariant after translation, rotation, and possibly reflection of the object. The quantitative study of form and form change comprises the field of morphometrics. For morphometrics to suc