1. Method for monitoring a spatial volume ( 10 ) enclosed by a pass-through compartment for persons using a plurality of camera pairs ( 11 , 11 ′) comprising cameras being disposed in pairs above the spatial volume ( 10 ), which are oriented from different spatial directions on the spatial volume ( 10 ) and are connected to computer hardware for digitalizing camera images ( 34 , 34 ′) detected by means of the cameras and for calculating, in each instance, a three-dimensional spatial image by means of superimposing the camera images ( 34 , 34 ′) of one camera pair ( 11 , 11 ′), in each instance, whereby a three-dimensional spatial image is prepared from the camera images of each one camera pair by means of the computer hardware and a height profile is determined therefrom, and whereby a common height profile being completed in that spatial points that cannot be represented due to shadows cast in one spatial image or height profile are supplemented using spatial images or height profiles of other camera pairs ( 11 , 11 ′).