Import .asc elevation model & contour lines

[HiAlHi]

Hi everyone!

I use Autodesk Map 3D 2013 with Raster Image.

The task I would like to accomplish is to import an ESRI ASCII GRID elevation model and create contour lines.

What I did so far:
- created a drawing with the 3d template.
- assigned LL84 coordinate system
- created connection to my dhm.asc file (ESRI ASCII GRID) with coordinate system CH1903 / height in meters
- add this as layer to the map
- assign theme for nice colors

So far this works but the first strange thing here is that the imported layer it slightly rotated. (Might be due to projection)

Next step:
- create contour lines

A new layer is created with the contour lines and this layer is not rotated so it does not match exactly the surface layer.

My questions are:
Why is the surface layer slightly rotated after import?
Why does the contour line layer not match exactly the surface layer?

Anything I am missing/doing wrong during import?

Thanks
Jochen