CALCULATING ORIENTATIONS IN UNDEFORMED STATE As shown by Ramsay (1967, Ramsay and Huber 1983), if the finite strains in the three principal planes are known together with the orientation of a line or a plane in these three principal planes (e.g. the angle between S plane trace and X in XY plane or between Y ans S plane trace in YZ plane and between S plane trace and X in XZ plane) then based on the information of these final angles and the strain ratio in each principal plane, the original angle that plane or line that made in the undeformed state can be known. The theoretical basis and the output of a related computer program are given.
