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chosen in the way that s; = s'1». For calculation of the air polygon the angles 
between the polygon sides have to be measured in addition. 
On the ground differences in height influence the results similar to radial 
triangulation." 
No discussion. 
After this the president annouced a paper from Mrs. Dr. Piazzolla Beloch 
(Italy) about graphical aerial triangulation of flat terrain. Since the paper was 
received too late and could not be introduced in the time schedule, it will not 
be read but only published in the Archives (see page (440) ). 
The subject is the following: 
A graphical method for the aerotriangulation of a flat ground is given, 
founded on a new and very simple construction of the homographic corres- 
pondence between two planes (photograph and air survey map), due to the 
author, and the easy execution of which permits practical application. 
For the triangulation with this method, only four fixed ground points are 
needed, and no element of the orientation of the airphotographs is required. 
Mr. Blachut reads the next paper about “Radar profile method and its 
application in photogrammetric mapping". Text see page (486)-142-1. 
Discussion. 
Prof. Zeller asks if there are new experiences in the determination of big 
distances with high precision using radar instruments. 
Mr. Blachut: This question refers to horizontal distances. Since the radar 
profile recorder gives a possibility to determine the flying altitude from which 
the foto-scale can be derived, this instrument might give a contribution to the 
precise determination of horizontal distances. 
Mr. Santoni: I like to know if it is possible to determine with the radar 
instrument the relative or the absolute value of the distance between the plane 
and the ground. In the second case it would be possible to determine in the 
restitution instrument the scale of the model. 
Mr. Blachut: Both results are possible. The radar recorder gives in the 
first place the exact distance between camera and terrain. By the application of 
corrections for the inclination of the surfaces with equal barometric pressure 
the result gives absolute elevations over sea level. It is indeed possible to improve 
the triangulation results by the application of this instrument. 
Mr. Brucklacher (Germany) reads a paper about “Investigations on the 
shrinkage of aerial film”. 
“The problem “Film or Plate” is of prime importance for the design and 
development of new photogrammetric cameras. Without conclusive proof, 
irregular film shrinkage has frequently been held responsible for errors which 
were found in measurements of mapping film. As a consequence, a number of 
survey cameras have been designed which are using plates. However, since the 
use of plates involves a considerable number of drawbacks in the photographic 
and plotting processes, ample experiments have been carried out at the Zeiss- 
Aerotopograph laboratories with the purpose to determine the shrinkage pro- 
perties of the films.