Quite often there is a need to transform the coordinate system of a CAD Model, Survey Model or Station Coordinates from one system to another (Usually National Grid). This can be accomplished with the prior knowledge of at least 3 or more points in both coordinate systems. Depending on the number of points selected to form the basis of the transformation, you will either be presented with the 2 point transformation interface or the 3 point (plus) dialog shown below.
If three or more points are selected, a dialog box similar to that shown below will be displayed.
The left hand side contains a list of the points which were selected to form the basis of the transformation matrix. Click each point in turn, entering new coordinates for the points in the boxes provided. As the new coordinates are entered the Helmhurtz least squares transformation is updated to reflect the new information.
After the new coordinates have been entered, press Ok. If you have opted to save the transformation parameters, you will be prompted for a name. This is so that at a later date you can transform similar data without the need to type in new coordinates for the data being transformed.
When the last set of values has been entered click back to another point in the list and check the transformation parameters. These are...

An overall error with units of m, comparing the calculated coordinates of each point, with the assumed values. I.e. it is the summation of the differences between the calculated coordinates of the points compared their assumed values. This value should obviously be as small as possible, although the final decision as to the degree of allowable error is up to the user. It should also be read whilst taking into account any scaling which was necessary. As the further the scale factor deviates from 1, the less confidence can be assigned to the transformation. 

The total distance the model will move along the X axis after the transformation has been applied. 

The total distance the model will move along the Y axis after the transformation has been applied 

The total angle the model will be rotated by to fit the target coordinate system. 

The further this value deviates from 1 the less confidence can be had as to the suitability of the transformation. It is therefore an indication as to the fit of the data. I.e. does the model need to be scaled in order to fit the new coordinate system. If you want to preserve the scale of your data, enable the Force Scale box and set the value to 1. The survey data will then be translated and rotated but not scaled. 
For QA purposes a Reporting tool is available to print the mathematical proof, giving details of the before and after coordinates along with the errors and other transformation parameters.
Having entered new coordinates for each of the points in the list, the transformation parameters will update to reflect output of the least squares transformation. An example of which is shown below. Note that one of the points has been removed from the transformation, by double clicking it's entry in the list of points.
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