In the "normal case" shooting (optical axes parallel to each other and orthogonal to the base) the objects photographed are fixed in an orthogonal Cartesian reference system having the origin in the left chamber, the y axis directed according to the optical axis of the left target, the x axis according to the base and the z axis in the third direction, orthogonal to the xy plane. In the upper photo: a shot with Wild P30 phototeodolite. The axis of the telescope, placed orthogonally to the optical axis of the camera, passes through the center of the target located on the second tripod. Bottom left: a shot with pinhole cameras. The room on the right has been placed in a central position in front of the facade, with the main distance chosen according to the desired scale for the frame. Bottom right: the reference system of the Wild C120 stereocamera, in a shot with an inclined optical axis.