I’m busy mapping some buildings in Belgium, and some Bing imagery is a bit skewed: it seems that the plane didn’t fly straight over the building when taking pictures. Now, as I want to map the building nodes as accurately as possible, do I need to position them at the base of the building, or rather at the roof? I’d think that the former one is more accurate, but I’ve spotted quite some roof-oriented buildings (I’m guessing because it’s far easier to do so).
You are right, orthophotos are usually produced according to the terrain surface and the aim is that the basements of the buildings will project correctly.