One of the techniques used in 2005 is called resistivity.  This is a way of "seeing" what is below the ground by passing electricity through the soil and measuring how much resistance it meets.  Because some materials conduct electricity more than others, we can use the results to make an underground picture.  Below you can see the resistivity picture of the 2005 site next to a map showing the property lines, houses and garages which were on the site in 1951.