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THE DESIGN OF PHOTOGRAMMETRIC PLOTTERS, DISCUSSION
transmission des renseignements ainsi que les servocommandes. Une attention spéciale
est accordée aux différentes manières de résoudre le problème de la réalisation pratique.
Enfin sont décris les deux appareils utilisant au mieux les avantages de cette nouvelle
méthode.
ZUSAMMENFASSUNG.
Im vorliegenden Aufsatz sind die Möglichkeiten für den Entwurf photogrammetri-
scher Auswertegeräte mit Anwendung mathematischer und elektronischer Methoden unter
einen allgemeinen Gesichtspunkt erörtert, um eine Grundlage für eingehendere Studien zu
schaffen. Nach einem geschichtlichen Überblick werden einzelne Probleme betreffend
Berechnungsformeln, Rechenmittel, Datenübertragung, Servosteuerung u.s.w. erläutert.
Ein besonderes Augenmerk ist auf die Konstruktionsprinzipien gerichtet und schliesslich
werden zwei Instrumenttypen hervorgehoben, welche die Vorteile der neuen Methoden am
besten ausnutzen.
Discussion
Mr U. V. HELAvA introduces the subject by
repeating shortly the main points of his invited
paper. Then he calls on Mr Dennis, as expert
on the panel dealing with electronic computa-
tion, to offer his comments.
Mr DENNIS: I feel some responsibility in this
matter, because as you have heard from Mr
Helava's remarks a great many of the problems
that have been dealt with in other ways in the
past have been shifted to the computor and now
great things are expected.
The concept I would like to leave with you
today is that of a computor as an element of the
machine design. The computor portion of this
analytic plotter is designed as a basic element
of the overall system; its function is to compute
the co-ordinates transformations made necessary
by the photogrammetric geometry.
The use of a digital computor for these com-
putations allows great precision. There are
many examples of computors designed as in-
tegral machine parts with fixed mathematics.
Some of these are the navigational computors
that are used today in aircraft, submarines and
missiles. These computors are somewhat similar
in that they have essentially a geometrical prob-
lem to solve. It should be emphasised that the
analytical plotter is a geometric problem; it is
not so much concerned with the dynamics of
the system, and this sets it apart from the
regulating type of computors that are so com-
monly thought of in the field of machine com-
putation, such as auto-pilots and things of that
nature,
Also, it should be emphasised that the com-
putor is not really designed to be a general-
purpose-do-everything computor for book-
keeping and miscellaneous mathematical prob-
lems, it is specifically designed for this problem.
One of the possible solutions to this computation:
problem is the use of the incremental type of
computor. The incremental type of computor
allows the next point to be computed with
knowledge of the previous points, and thus
allows great computing efficiency. Inputs to
such computors are of a pulse nature, that is
incremental pulses; they are by two-phase type,
so that the direction of motion can be distin-
guished. It is necessary to insert fixed constants;
these can be done through either key-boards or
dials and instrumental generators.
Another thing that works well with a com-
putor of these requirements is the use of a
magnetic drum, because you have need for a
fixed programme. It can be optimally pro-
grammed at the beginning so that the serial
nature of such computations is very well suited.
One feature, the flexibility of the digital
computor allows, is that more than one perma-
nently recorded programme may be used, and
solutions may be made using the same computor
hardware; for example, the relative orientation
achieved by matrix multiplication may be done,
and this is done before the computor is used for
the main programme. Therefore, the same com-
putors hardware can be used and the results
stored in proper locations in the memory for the
execution of the main programme.
The concept of the AP.1 computor is, there-
fore, to have a unit as a fixed element of the
overall machine, of such a design that it fills its
function in the overal system without the user
really being aware that the computor is in
existence.
Mr U. V. HELAVA: I would now like to call
on Dr Deker, an expert on mechanical compu-
tation.
Herr Dr DEKER: Herr Präsident, meine
Damen und Herren! Der Gedanke, mechani-
