I am new to creating surfaces in c3d with Google Earth (GE). My coordinates are correctly set (NAD83 Oregon State Planes (Polyconic), North Zone, Intn'l Foot) and my surfaces come out beautiful except for one thing - where the actual survey and google earth may differ by a few feet, c3d is off by more than a hundred. For example: The actual contours range in elevation from 184' to 196'. In panning GE the elevations range from 180' to 200'. In C3d, however, they range from 55' to 61'. What's up with that?
Check your settings and orientation in Google Earth. You need to ensure that the Elevation Exaggeration setting = 1, and that your viewpoint is straight down, with North up before importing data.
I noticed that the elevation errors reported in the original post would be about right for a feet to meters conversion. Is it possible that your drawing units are metric, or that the labels are displaying that way?