11 
Said parameters are analytically deducible from those of the take dihedral, therefore 
practically from the current topographic parameters of external reciprocal orientation of 
the ground take arrangement adopted. But they also include the value of f (internal 
orientation) in the abscissa r (therefore r — f ctg y) and therefore the reduced represen- 
tation thus obtained, completely characterizes the stereo-retake and so it becomes possible 
to carry out on it all the geometrical-projective operations of the homographic cor- 
respondence between nuclear beams and between homologous points. 
5 
  
  
Fig. 7. Reduced projective diagram of the open-face take dihedral. 
¢) Instrumental analogical solution. 
Also with the true homographic representation so reduced to the strictly indispensable 
dimensions, (on account of the consideration of the fulcrums) the ordinary means of 
graphism would be stil far away from allowing, with their scarce accuracy, the total 
utilization of the normal photographic resolution. 
There is therefore indispensable for such an utilization, a mechanical instrument of 
photogrammetrical centesimal accuracy that permits to reproduce analogically the pro- 
jective correspondence of the nuclear beams in the same reduced outline. 
The homologo-comparator has been planned and constructed for this scope by the 
O.M.I. according to a particularly fortunate instrumental scheme, since, beside offering 
the primary function of a homologoscope, offers also the secondary function of a centesimal 
measurer of the plate's carthesian coordinates and the accessory function of a principal 
point triangulator. The adding of a mirrored stereoscope would also make it become a 
stereocomparator. 
The employ of the homologo-comparator as a simple comparator is made particularly 
expeditious immediately after the homologs have been identified, when a particular 
intrinsical coordinates’ system is assumed for the spatial reference from the numerical 
plotting. 
Fig. 9 shows in its three fundamental phases the genesis of the homolog-comparator 
instrumental scheme, as shall be better illustrated later on, and supplies examples of 
homologs identification as well as of corresponding zones on the two take frames. 
d) Corresponding zones om the photographic take frames. 
Definitions: 1st. A ground take arrangement with non-parallel axes, is defined intrinsıc-