Affine general parametric transformation 9624 XT = A0 + A1. XS + A2.YS; YT = B0 + B1. XS + B2.YS; where XT , YT are the coordinates of a point P in the target coordinate system; XS , YS are the coordinates of P in the source coordinate system. Reversibility: The parameter values for an affine transformation cannot be used for the reverse transformation. However, the reverse transformation is another affine transformation using the same formulas but with different parameter values. The reverse parameter values, indicated by a prime ('), can be calculated from those of the forward transformation as follows: D = A1 . B2 - A2 . B1; A0' = (A2 . B0 - B2 . A0) / D; B0' = (B1 . A0 - A1 . B0) / D; A1' = +B2 / D; A2' = - A2 / D; B1' = - B1 / D; B2' = +A1 / D. See Section 2.4.2.1 of EPSG Guidance Note 7. 2 2 A0 8623 A1 8624 A2 8625 B0 8639 B1 8640 B2 8641