What datum (reference ellipsoid) does Google Earth use?
According to Does Google Earth use WGS84 (G1762)?:
Google Earth itself doesnt do any projection or anything, but by convention all the data (imagry, KML etc) 'imported' into Google Earth uses WGS84.
The heights on google earth refer to EGM96 and are, therefore, Geoidal heights. The lat/long are referred to the WGS 84 ellipsoid.