a 19. 
for the automatic addressing of the same points, This technique is 
very useful in cases where the orientation of a number of planes is 
sought, e.g. in crystallography or in determination of strikes and dips 
or rock formations. A possible procedure is to select first the 
surfaces of interest by registering the coordinates of the centroids of 
these surfaces and introducing an identification number for each surface. 
After that the program automatically positions in a predetermined 
sequence the measuring mark on these surfaces, and the operator can 
measure the points needed for the determination of the desired angles. 
If more than three points are measured per surface, the angles and the 
estimators of their accuracy are computed in near-real-time. Simul- 
taneously with the numerical output of these quantities a graphical 
output may be generated (e.g. in strike and dip determination a plot of 
the results in stereographic projection will facilitate the interpreta- 
tion of the results since the surfaces with similar strike and dip 
fogs will be represented by points clustered in the same area of the 
plot). 
In engineering as well as in biometrics similar techniques may 
be used for deformation measurements or determination of changes in 
volumes or comparison with standards. They are especially effective 
when using images made with cameras with smaller formats (e.g. stereo- 
metric cameras). Three or four of them can be placed on each plate 
carrier of an analytical instrument and as many stereo-models may be 
reconstructed at the same time. The basic real-time program will 
address automatically the points with the same model coordinates in 
different models, by automatically changing from one set of orientation 
parameters to the other on the command of the operator. In that way 
only the differential changes of an object, registered on different 
stereopairs, have to be measured by the operator or the automatic con- 
troller. Under the same circumstances if an object is photographed 
from several sides to obtain the full coverage, continuous plotting or 
digitizing may be achieved by switching from model to model. When the 
point on a line is reached beyond which there is no stereo-coverage in 
one of the models, the operator can activate the automatic exchange of 
parameters in the basic real-time program. That will result in the 
addressing of the point with the same model coordinates in the chosen 
model. 
The ability to choose reference systems other than those 
defined by the mechanical axes, is also quite significant both in 
respect to the movement of the measuring mark in the model space and in 
respect to the graphical presentation or digital recording of results. 
The reference system in which the absolute orientation of models is per- 
formed is not always the reference system in which one intends to plot 
or digitize the data. In analytical instruments once the model is 
oriented one can introduce other reference systems or, in other words, 
one can make an auxiliary transformation of coordinates in real-time 
without upsetting the established absolute orientation. For instance, 
when close-range photogrammetry is used in architecture, it is often 
desirable to plot the details on the facade of a building in a reference 
plane that is approximately coincident with the facade. An additional 
transformation of photo-coordinates inserted into the basic real-time 
program, can cause the handwheels to move the measuring mark along two 
chosen axes in that reference plane and the footwheel to move the 
measuring mark along the axis perpendicular to that plane. Similar free