Anyone who's seen the new Google maps has no doubt taken note of the incredible amount of three-dimensional detail in select American cities such as Boston, New York, Chicago, and San Francisco. They've even modeled the trees, bridges and some of the boats in the harbor! Minor architectural details are present. It's crazy.

Looking at it up close, I've found there's a rectangular area around each of those cities, and anything within them is 3Dified, but it cuts off hard and fast at the edge, even if it's in the middle of a building. The edge of the rectangle is where the 3D stops.

This leads me to think it's being done algorithmically (which would make sense, given the scale of the project, how many trees and buildings and details there are), and yet I can't imagine how that's possible. How could an algorithm model all these things without extensive data on their shapes and contours? How could it model the individual wires of a bridge, or the statues in a park? It must be done by hand, and yet how could it be for so much detail!

Does anyone have any insight on this?