What we're all saying is that there is no way you can do it just with google maps. If you insist on using google maps, you'll have to add something to it, and a compass rose is pretty good, especially if it has marks between, for instance, south and southwest.
Or you can do it without google maps using tvfool.com.
But in any case you need to get the actual azimuth, and the online tool is good. So is the tool in the DirecTV receiver's satellite setup.
Here's a nice one, and jeez, this is what it looks like after they reduce it in size!