I chose that one because here, we dig footers down to 36" to protect for frost. Waterlines get 40"-48" of cover. And I agree, I've never seen frost that deep. The point is though, that you can get frost well SOUTH of the Mason Dixon Line. A couple hundred miles NORTH of that, it can be lots deeper. :cool2
See if you like this frost map any better. I have seen it pushing 18" here, but it was a really cold winter.
And to get things back on topic, the second pic is of a Link Belt 135 zero tail swing excavator. It was a rental that we had on the job for a couple of months. Nice, because it was on rubber tracks, so it could walk all over the neighborhood without tearing up the streets. I didn't get much time on it, but I got enough to say I have a positive impression. (Only real complaint is that they only put steps on the side of the undercarriage at two of the corners. If you want to stop and climb down, you need to have the boom lined up with the tracks. Stop it with the boom swung to the side, and there's no step there. How much would it cost to put one at every corner??)