The problem here is not about the datum. It is about how you get the coordinates. You can’t just take them directly from the image on google earth. You need a precission GPS equipment certified, a corrected satellite image or other means of point designation like and Air to ground litening pod from a fighter aicraft.
This precission on the coordinates is measured by the TLE(Target Location Error) and it will let you know how precise are the coordinates you are getting.