A duct fan comprises a housing having substantially the shape of a rectangular parallelepiped and inside thereof an impeller and a motor for rotation thereof. The HA maintains a binding between the home address and a special care of address, where the host ID of MAP-CoA is the identifier, and where the network ID of MAP-CoA is a special code. A computing device matches corresponding pixels in the images by using the local uniqueness of the pattern to produce a disparity map.