(rail transport) A railway passenger car made so as to facilitate seeing the scenery en route, sometimes with glass sides or with a kind of open balcony at the rear.

plural of observation post

plural of observation deck

A rudimentary building used by people making field observations.

plural of observation hut

The situation in which a phenomenon being observed for study is unwittingly influenced by the presence of the observer.

(military) A type of balloon that is employed as an aerial platform for intelligence gathering and artillery spotting.

plural of observation balloon

plural of participant observer

Alternative form of participant observer