Our guess is they have a car with a panoramic camera/multiple cameras on top. They drive down the road and it takes a photo every 100m or so. Will still take a long time to do the whole planet though

And a lot of hard disk space.
The Vegas stuff is a bit peculiar. If you find the Monte Carlo (pretty much opposite the MGM Grand on LV Boulevard) it looks like it's miles from the road, but in reality it's just a few metres away.
Jim