1978 ISP COMMISSION V INTER-CONGRESS SYMPOSIUM - STOCKHOLM SWEDEN 
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Grün: What is the amount of the angle of convergence when the stereo im- 
pression vanishes in the TRASTER system? 
Vigneron: The same as with conventional stereoplotters. 
Linkwitz: The instrument which you describe is very powerful, but also 
very sophisticated. How much time would an occasional user need for train- 
ing, and become equipped to do a job like you describe? 
Vigneron: One advantage of analytical stereoplotters is that they do not 
require specific training due to permanent and easy control by the computer. 
For photogrammetric operators, in a maximum of one day they are able to 
operate. There is no specific need for training. I should point out that 
a lot of the work cannot be done in other instruments, so a comparison is 
not really valid. 
Chisholm: In the TRASTER, control of the floating mark in x, and y, is by 
a ball on an air cushion. Can you give us an indication of the repeata- 
bility of operator pointing using this system, as this is perhaps more 
critical in industrial photogrammetry than in normal topographic work? 
Vigneron: For operators who have used conventional wheels for several 
years, it sometimes takes a few days. But there are no difficulties in 
making the measurements. The repeatability is a few microns, exactly the 
same as if you use the wheels. It takes two or three days to adapt for 
following a contour line, for example. To go from one point to another 
the repeatability is exactly the same. 
Kratky: You say to re-orient a model takes about three minutes. Does this 
mean that the photograph has been removed and then put back again so you 
measure all the fiducials? 
Vigneron: Yes. 
Kratky: Even if you leave the photographs in the instrument? 
Vigneron: Yes. You just have to measure the fiducial marks. Of course 
you must measure the fiducial marks very accurately. 
Kratky: In your instrument the magnification is much larger than in any 
other instrument. That would mean that you require more energy for the 
illumination system. How do you solve the problem of cooling? What are 
the temperature changes? 
Vigneron: Around the projector system we have a cooling system, and this 
means that we never have deformations. 
Kratky: Is there any temperature change between the time when you start, 
and after the instrument has been in use for about six hours? 
Vigneron: No. Generally you have to wait about ten minutes after you 
switch on the equipment for the computer anyway. 
Kratky: It doesn't affect the film? 
Vigreron: No. 
Kratky: In one of your pamphlets you make a distinction between relative 
orientation and the "shaping of the plastic image" devised by Hottier. 
Could you elaborate on this? 
Vigneron: The distinction in the pamphlet has no significance.