Request for automatic calculation of transformation parameters for rotate, scale for transform operation between Local Coordinate System <> Geographic Coordinate System. Change request 884946.

Now local Transforms and Pushing or Pulling Geographic Coordinate Systems to or from Reference Attachments require scale to be 1.0. This doesn't work for coordinate systems based on UTM as scale factor is 0.9996 for these systems and need to be adjusted to 1.0 for local transform.

The Helmert transformation as defined in the Geographic Coordinate System expresses the transformation from PE, PN to E, N (the Helmert transformation is expressed from final cartesian coordinate(PE, PN) to Easting/Northing at the output of the projection)

In order to remove the translation component hidden by the fact the scaling is not relative to the origin we distribute.

E=0.9996*PE -0.9996*originY+Y

N=0.9996*PN-0.9996*originX+X


So in fact the linear transform is still possible for Helmert transform if the offset is adjusted.

Custom coordinate systems are much better approach to reference move, scale, rotate as it allows to use background maps like Bing, WMS without need to move elements.