Guerra, Francesco 
  
5 THE REFERENCING - CORRESPONDENCE PROCEDURE 
This procedure is from an algorithm point of view practically identical to the referencing-transformation, which it 
differs from only in two points: 
e the interactive management of the correspondences, 
e the type of global transformation used. 
The procedure of referencing-correspondence is based on the application of a global transformation to which a local 
transformation follows; the introduction of this procedure is motivated by the desire to not destroy the image of the 
paper in the cases where the transformations to introduce are of an elevated quantity. If, therefore, the purpose that has 
motivated the definition of the procedure is the preservation of the form, it is opportune to apply this principle not only 
in the local phase, but also in the global phase. Only some types of global transformations are compatible however, the 
conform ones. Among these, it was decided to admit the translations, the rotation and the variation of the isotropic 
scale. 
6 HISTORIC CARTOGRAPHY AND NEW TECHNOLOGIES 
The 2WIN software aids in identifying corresponding points and therefore also the calculation of the co-ordinates in the 
system of the reference map. 
These two actions: 
e identify points, 
e find the co-ordinates of these points, 
the fundamental operations which are carried out on the cartography are: 
e localisation, 
e measurement. 
The software designed and implemented in this way realises in a conclusive way the idea of returning to the historic 
cartography a strict metric support without however modifying the original aspect. This would suggest reflecting on the 
ities offered by the use of informational instruments in the field of , and not of historic nature. 
     
       
Arbol PN Acad 
figure5. 2W user's interface. The crosses in the middle of the windows show the homologous points 
APPENDIX 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B5. Amsterdam 2000. 343