Element: projection.datum_transform
Element: projection.datum_transformstring
A string indicating which transformation is to be used when applying a datum shift during co-ordinate conversions from one ellipsoid to another (see projection.datum).
The following table lists the availabe datum shift transformations.
Value
No of
ParamsTransformation
epsg9603 3 Simple 3-parameter translation epsg9604 3 Molodensky transformation epsg9605 3 Abridged Molodensky transformation epsg9606 7 Position Vector Helmert transformation
aka Bursa-Wolfepsg9607 7 Co-ordinate Frame Helmert transformation
Unless specified otherwise, the default transformation for a projection is the 3-parameter Molodensky transform, string value epsg9604, although until datum shift parameters have been supplied for the projection a query on projection.datum_transform will return an emtpty string.
Changing this value may change the projection depending on other projection attributes.