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THE DESIGN OF PHOTOGRAMMETRIC PLOTTERS, HELAVA 131 
to be the only possible solution. Although other solutions are now possible, the advantages 
of the early proposal are still remarkable. The output motions are relatively small and 
slowly changing. This is a favorable situation from the servoing point of view and also 
makes the solution of the computation problem easier. The input motions are easy to 
control by the operator. The design is symmetrical and does not add complications to the 
bridging procedure. It is also a true feedback system in the sense discussed in connection 
with alternative A. Obviously, the general solution may be obtained only by employing 
additional outputs to get X, Y, and Z. However, in the opinion of the author, the solu- 
tion of this part of the problem is better solved by using a separate program and mecha- 
nization, for reasons not pertinent to this discussion. 
There are numerous other solutions. Their number becomes particularly extensive if 
we consider also the possibilities where all the input quantities are not accompanied by 
corresponding physical displacements. The input in such a case consists of numerical 
values only. The merits of a number of solutions not mentioned above have been studied 
by the author. No reason has been found to expect that any solutions that are signifi- 
cantly better than the ones considered above would be discovered. 
5. Outlines of specific solutions. 
Many different types of plotters may be designed following the principles discussed 
above. Advantages are to be expected from the application of these methods in many 
fields of photogrammetry and, undoubtedly, these potentialities will eventually be ex- 
ploited. In some directions, however, the prospects are overwhelmingly attractive, and 
the development will proceed first in those directions. The two types of plotters that best 
utilize the potentialities of the principles discussed above may be called a super-plotter 
and an automatic mapper. 
A super-plotter will be an instrument that aims specifically for the utmost in ac- 
curacy and flexibility of programs. It will have a high precision mechanical viewing- 
measuring device and a computer that is able to handle complicated relationships between 
the final coordinates and the photo coordinates. It has compensation devices for all known 
errors and programs to utilize the method of least squares in the determination of the 
parameters. Its use will be in the field of high accuracy photogrammetry and in the 
solution of complicated problems not solvable by other means. 
An automatic mapper will exploit in part the same advantages of the analytical 
plotter as the super-plotter and partly some others. First of all, it will make use of the 
fact that the plotter is capable of accepting the values of the parameters in the numerical 
form. To make full use of this outstanding feature the “inner orientation” of the photo- 
graphs in the plotter must be done to a high degree of accuracy. This can be accomplished 
by using the measuring devices of the instrument itself for a measurement of the position of 
the photograph. Secondly, the automatic plotter will utilize the fact that in a mathemat- 
ical plotter the photographs need not be tilted, rotated, or shifted. This feature facili- 
tates the handling of the source material. Thirdly, the least squares solutions may be 
used in the determination of parameters. Finally, the flexibility of the basic principle is 
utilized when incorporating image correlation and facsimile printing devices. 
Examples of instruments of both these types are being constructed and may be ex- 
pected to be operational in the near future. At the moment of writing, the details of 
their final designs are not published and so a discussion on this matter is not possible. 
However, when the details are published, the items pointed out above will help in their 
classification and evaluation. 
6. Concluding remarks. 
In this paper an attempt has been made to present the main points in the develop- 
ment of photogrammetric instruments and to gather and organize widely-diversified 
Archives