Are you concerned about where you go to arrive if you dig a very deep straight infinitous hole on Earth? Your problems are solved! [sic]
Thus begins the site "If I dig a very deep hole…" Using this Google Maps application, you can tell where you would eventually end up if you started digging straight down (ignoring all that heat, pressure, and bothersome magma) and out to the other side. So, for example, if you start digging in Lyman, South Carolina, you would wind up in the Indian Ocean just off the coast of Australia.
I’m just guessing here, but I believe that this application simply changes the sign (direction) for lattitude and longitude. Let’s assume you start digging at Lat 36 degrees, 00′ 56.61" N and Long 114 degrees, 44′ 17.08" W (that would be Hoover Dam.) In theory, you should wind up at Lat 36 degrees, 00′ 56.61" S and Long 114 degrees, 44′ 17.08" E. That’s a fairly easy calculation (assuming the earth is a perfect sphere, which it isn’t.