Methods and apparatuses for ensuring the dimensional constancy of multisegment physical structures, in particular aircraft structures, during assembly are disclosed. The method includes setting up a spatially-fixed three-dimensional coordinate system which encloses the subsequent assembled physical structure and introducing a plurality of segments of the physical structure to be assembled into the spatially-fixed three-dimensional coordinate system. The method includes recording the positions of the individual segments and the positions of already assembled groups of segments repeatedly within the spatially-fixed three-dimensional coordinate system during assembly. The method includes correcting the position of a respective segment or of a respective already assembled group of segments if a respective record shows that the positions of the respective segment or of the respective already assembled group of segments is outside a tolerance band, which is predetermined in accordance with a desired dimensional constancy, by a respective predetermined nominal value.