[zodPod]

That's a good question. Not sure!

[Isamu]

Best I could find right now: Lidar point cloud data

http://www.dcnr.state.pa.us/topogeo/pamap/lidar/index.htm#cl...

Looks like Allegheny county was done in 2006.

What is nice about the point cloud data is that they classified each point as ground, road, water, etc