A Similarity Transform, as defined by the IOGP's EPSG working group, is a four parameter mathematical transformation that can be used to identify the relationship between two given coordinate reference systems.
Similarity transformations are also available in two jobs under the name "Helmert Four Parameter." In the Point Database Scale and Translate job and the Vector Data Conversion job (manual transformation option), the parameters are entered manually and can only be saved within the job. The Similarity Transform method allows users to create and save a custom Similarity Transformation object in the Datasource for use across jobs, or for export to other users.
Parameters needed to define a Similarity transformation are:
|
Parameter |
Often Noted as |
|
X Translation |
dX |
|
Y Translation |
dY |
|
Z Rotation |
rZ |
|
Scale |
k |