Mapping position data to a scaled transform

[tokola]

I have the following problem and was wondering if there is a solution. I want to use a scaled version of a top-down map, and have all position data transformed to the scaled map. A visual representation is included in an image. The gray/green map is the scaled version of the actual 3D space, which is superimposed with transparency (delineated also with a red line).

The map has a scale factor of [1,1,1.2]. How can every position passed to the map be automatically transformed to correspond to the correct spot? I use preScale but probably in the wrong way, as it scales the original 3d node, too.

I would appreciate if there is a way that does not involve multiplying every single value passed with a factor, as this would entail a considerable amount of tweaking.

Thanks!