COMMISSION V 
INVITED PAPER 
C. SENA POLITECNICO DI TORINO 
ISTITUTO DI GEODESIA, TOPOGRAFIA E FOTOGRAMMETRIA 
DEL POLITECNICO DI TORINO 
USE OF ANALYTICAL PLOTTERS IN ARCHITECTURAL PHOTOGRAMMETRY 
A number of Authors have already pointed out that, during the last few years, Pho- 
togrammetry and Informatics have merged into a profitable match, at higher and 
higher levels. 
This evolution has led to the implementation of Analytical Plotters, in which Pho- 
togrammetry and Informatics reach a high degree of interaction in the solution of 
the problem of geometrical survey in general, utilizing pairs of photograms. 
| deem it useful to remind briefly what we mean for « Analytical Plotter »: it gene- 
rally includes the following instruments: 
a) stereocomparator 
b) digital data processor 
C) coordinatograph 
d) various components, such as interface between stereo and processor and bet- 
ween processor and coordinatograph, checking, reading and communication de- 
vices. 
When the two stereoscopic photograms have been placed into the stereocompara- 
tor this surveys the coordinates of the réperes and of a given number of predeter- 
mined points; it is then possible to obtain the so called « photo-coordinates » (i.e. 
referred to systems pertinent to the plates themselves) of such points. 
Principal distance of camera, distorsion curve of lens and position of principal point 
being known, if we introduce aproximate values of the coordinates of the camera 
stations and values of the rotation parameter of the camera on the two positions qi, 
wi, Ki, and 9» 0», Kz, it is possible to set a relative orientation program on the pro- 
cessor, on the basis of the «photo coordinates » given by the stereocomparator. 
The result of said program being the reckoning and subsequent analytical elimi- 
nation of the paralaxes for the various couples of homologous radiuses taken into 
consideration and the calculation of differences Aw, Aw and AK. 
After the problem of relative orientation has been solved, if both « ground-coordi- 
nates » of an appropriate number of points (topographical coordinates of control 
points), and the relevant couples of « photo-coordinates » (derived from stereocom- 
parator-processor) are read in to processor, it will then be possible to put the model 
to scale and to set it in its right position, following a program of absolute orientation. 
We can now store the matrices of parameters for subsequent correct reading out. 
Thus, a REAL-TIME program (40-50 cycles per secondo) allows the reading out of 
the points of the model to the desired scale, on the drawing table. 
As a matter of fact, it is essential to point out that the above complex cycle of opera- 
tions being a theoretical scheme only, it clearly differs from real procedures adopted 
on the instruments available at present (A.P.C./OMI - Bendix, D.S. Galileo). 
It is widely known that Analytical Plotters present many advantages (together with 
some disadvantage) as compared to analogical instruments: among the advantages 
there is freedom from focal length of camera, from plate size, from lens distorsion, 
etc. for some of these paramenters can be varied according to program. 
Other limitations, peculiar to analogical instruments, are also overcome. 
But, beyond the above general advantages, let's now see why Analytical Plotters are 
likely to become more and more interesting specifically in the field of Architectural 
surveys.