oh yes this is really important. i think google map is only an orientation.
you could switch in the time line back and look is your house exactly on the same location or not. i dont know, could be for sketchup exist a plugin for inserting exact cordinates from GPS. when you will realy work exact, i think you need a very exact GPS and compass.
here a link to an exact GPS (1 inch)
http://www.popsci.com/technology/article/2013-08/global-positioning-down-inches