How accurate is GPS?

How accurate is GPS?

I am just playing around with a GPS datalogger which allows you to track your movements... OK before you get all "Conspiracy Theory" on me, you can use a datalogger to keep track of where you have been, cross-reference that data to photos you take, and then embed that GPS data into the photos so you know where each photo was exactly taken.

So I turn the device on, while sitting at my kitchen island. The first point it picks up, I load into Google Maps and look at that... not only is it close, it is bang on. I am sitting in the NE quadrant of my house, and according to Google Maps, and the funky little green arrow, that really is where I am sitting.

How accurate is GPS? Darn Accurate!