air observation post observer

forward observer (FO), forward observation officer; (artillery) observer / spotter

forward observation post observer

observation point / observation post (OP)

air observation post

air observation post flight

air observation post squadron

command-and-observation post

artillery observation post

control observation post

amount of command of observation post

antiaircraft observation post

battery observation post

cross-observation post

flash-spotting observation post

fort-observation post

forward observation post

groupment observation post

armored observation post

artillery group observation post

artillery groupment observation post

artillery observation post vehicle

forward artillery observation post

mobile artillery observation post

sound ranging observation post

vehicle-mounted artillery observation post

command p.-observation post

scientific observation post

aiming post lamp / aiming post light

air guard observer

air observer

air tactical observer

upper air observation