CAD file format specifications?

[Anthra Norell]

Hi,
   Anyone working with CAD who knows about numeric data entry? I have 3d 
coordinates of a construction site on a slope (borders, setbacks and 
isometric elevation lines). Someone made me aware of Google's Sketch Up. 
It looks very attractive for the purpose of architectural planning, 
especially suited to create visual impressions. Doodling seems easy. But 
I have to start with modeling the terrain and the envelope and the only 
way to do that seems to be in one of several CAD file formats (skp, dwg, 
dxf, 3ds, ddf and dem). So I need to cast my numbers into one of these 
formats. Any suggestions?

Thanks

Frederic