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
Sketchup – Save SKP – Import/Link into Revit

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

The author of RevitToday posted a comment on one of my posts yesterday, so I went to the blog to have a look.
He has provided a couple of extensions you can download:

Export XYZ from Revit 2011

This extension for Revit 2011 exports all coordinates of Point Based Generic Models to an Excel file.

You can locate Point Based Generic Models in your whole model. You are able to nest such a Family within another. These points are exported as well when you make this family Shared.

You can download it here. (It has been compiled for Windows XP 32 bits)

Import coordinates into Revit 2011

I updated the Revit 2010 extension for importing coordinates from a TXT file. You are free to select a family of your own. It should be a Point Based family of course.

You can download the extension here.

(It has been compiled for Windows XP 32 bits)