Here is a good guide on how to install the Google Earth Extension in AutoCAD.

There is a workflow which allows the topography from Google to be placed into Revit. You could try:
AutoCAD with Google Earth Extension – Export DWG – Import/Link into Revit
OR
Sketchup – Save SKP – Import/Link into Revit

Installing the Google Earth Extension for AutoCAD-based products – It is Alive in the Lab