Note: These formulas have been transcribed from EPSG Guidance Note #7-2. Users are encouraged to use that document rather than the text which follows as reference because limitations in the transcription will be avoided.¶¶Transformation of coordinates from one geographic coordinate reference system into another (also known as a "datum transformation") is usually carried out as an implicit concatenation of three transformations:¶[geographical to geocentric >> geocentric to geocentric >> geocentric to geographic]¶¶The middle part of the concatenated transformation, from geocentric to geocentric, is usually described as a simplified 7-parameter Helmert transformation, expressed in matrix form with 7 parameters, in what is known as the "Bursa-Wolf" formula:¶¶   (Xt)             (  1       -Rz    +Ry)      (Xs)     (dX)¶   (Yt)  =  M *  ( +Rz      1      -Rx)  *  (Ys)  + (dY)¶   (Zt)              ( -Ry   +Rx       1 )      (Zs)      (dZ)¶¶The parameters are commonly referred to defining the transformation "from source coordinate reference system to target coordinate reference system", whereby (Xs, Ys, Zs) are the coordinates of the point in the source geocentric coordinate reference system and (Xt, Yt, Zt) are the coordinates of the point in the target geocentric coordinate reference system.  But that does not define the parameters uniquely; neither is the definition of the parameters implied in the formula, as is often believed.  However, the following definition, which is consistent with the “Position Vector Transformation” convention is common E&P survey practice, ¶¶(dX, dY, dZ)   :Translation vector, to be added to the point's position vector in the source coordinate reference system in order to transform from source system to target system; also: the coordinates of the origin of the source coordinate reference system in the target coordinate reference system.¶¶(Rx, Ry, Rz)   :Rotations to be applied to the point's vector.  The sign convention is such that a positive rotation about an axis is defined as a clockwise rotation of the position vector when viewed from the origin of the Cartesian coordinate reference system in the positive direction of that axis; e.g. a positive rotation about the Z-axis only from source system to target system will result in a larger longitude value for the point in the target system.  Although rotation angles may be quoted in any angular unit of measure, the formula as given here requires the angles to be provided in radians.¶¶M                  :The scale correction to be made to the position vector in the source coordinate reference system in order to obtain the correct scale in the target coordinate reference system. M = (1 + dS*10^-6), where dS is the scale correction expressed in parts per million. ¶¶<<<<<This text continues in the description of the Coordinate Frame Rotation formula>>>>>