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RECENT DEVELOPMENT OF APPROXIMATE INSTRUMENTS, ZORN 183
relative orientation are introduced in advance, and thus are not determined from given
heights.
Very interesting comparisons between Multiplex and Stereotope were published by
Prof. E. Gotthardt (B.u.l. 1958-1959). It was striking to note that the results in altime-
try were superior for the Stereotope and that the time needed was from one third to
one half that required for the Multiplex. The fact that the tests were carried out by
students must, however, be mentioned.
A disadvantage of both Stereotope and Stereomicrometer was previously thought
to be the amount of preparation and calculation work. Originally the Stereomicrometer
was in this respect easier: No point transfer, simpler scale computation, etc. Moreover,
the hyperbolic graduation of the height scale made the height calculation very easy.
Zeiss has now produced a computer for the conversion of parallax to height and vice
versa. This facilitates the work considerably. It is difficult to say now which of the two
instruments is the most elaborate.
Ackermann published a paper on the application in the Stereotope of data obtained
by aero-triangulation. For a great part this paper is also applicable for the Stereomicro-
meter. In my opinion the use of the base height ratio, the flying height over reference
and the height of the reference point can be taken with advantage from the aerial trian-
gulation but I doubt wether setting of the height correctors by means of these data will
be economical.
Dr. Wassef has published a paper on the theoretical backgrounds of our subject:
“Theoretical Inquiry into the Intrinsic Precision of the Photogrammetric Techniques”.
Dr. Wassef now presents: “Theory and Principles of Design of Realizable Photo-
grammetric Instruments Deriving from the Polynomial Representation of the Scale Para-
meter”.
In this paper Dr. Wassef demonstrates how the theoretical background of his former
paper can be applied in practice.
The S.0.M. at Paris has produced an instrument according to a design of Mr. Mas-
son d'Autumne, who will inform us with more details.
As main points for the panel discussion were recommended.
1. Definition of the so called 3rd order instruments.
On a meeting at Brussels, June 1959 was proposed:
Restitution instruments, offering the possibility of continuous tracing of the plani-
metry and altimetry, but not based on a rigorous (that means geometric exact) re-
construction of the two perspective bundles of rays.
In connection with this we may pose the question: *What are the qualities and cha-
racteristies required in general?"
2. A classification of approximate instruments.
In my lectures I use this classification:
a. Instruments using only one camera:
(Sketchmasters, Tracing Stereoscope, Spatial pantograph Dubuisson)
b. Radial Line Plotters (Kail, Hilger and Watts, French Cadastral Service).
c. Stereo sketch masters.
(Stéréoflex, Multiscope, Konschin).
d. Stereometer instruments without correction devices.
(Stereopret, Contourfinder ete.).
e. Orthographic instruments.
(K.E.K. and Wernstedt-Mahan).
f. Stereometer instruments with correction devices working in a plane.
(Stereotop, STD-2 etc.)
