end- 
nts. 
d to 
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the 
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| rectifier. 
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that. After 
Santoni the 
r do you 
iormal one 
'ectification 
e or aerial 
' ( can be 
Stéréoflex, 
is that for 
of the ter- 
the metric 
statement. 
| if there is 
vill want to 
oped to be 
ust to show 
apparently 
ı time, so I 
nagination. 
u know the 
'rtical posi- 
ent mirrors 
ind against 
two photo- 
same time 
le just over 
of the pan- 
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that means 
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300 metres, 
d. 
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>, only we 
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it Géogra- 
ument has 
  
RECENT DEVELOPMENT OF APPROXIMATE INSTRUMENTS, DISCUSSION 185 
been used mainly for a photo scale of 1 : 50,000 
and a map scale of 1 : 100,000. It is, therefore, 
a reduction, a reduction of two times. The time 
needed for the orientation of such a model was 
in general thirty minutes, and the output was 
about 100 square kilometres per day, that means 
about 40 square miles per day. 
After this talk, I should like to have answers 
to the questions: were those maps compared 
with others? Were there interpretation errors? 
What do you think is a reasonable ratio between 
the image observed, the ocular magnification in 
general and the map you are making? I think 
that is an important question for accurate 
instruments as well as for approximate instru- 
ments. 
Mr Masson D'Autume and Mr Makarovic gave 
answers to the theoretical deformations. They 
determined the theoretical deformations which 
you get in instruments of this kind. Mr 
Makarovic has presented a paper on this subject. 
It is rather a complicated paper with a lot of 
formulae in it, and I am sorry that I have not 
yet had time to check the formulae although I 
have no doubt they will be correct. I think it is 
good to read Mr Makarovic's conclusion of the 
paper, as this contains no formulae at all and 
can be read quite easily at a meeting such as 
this. The conclusions are as follows. “For a 
convenient correction of space model deforma- 
tions on instruments of the third order with the 
space solution, it is absolutely necessary to con- 
sider the elements of external and inner orienta- 
tion. Mechanical correctional installations for 
these elements are not convenient because we 
can place them directly in the instruments. We 
can take the element of external orientation from 
the space aerial triangulation, the most econom- 
ical method of determination of control points. 
The instruments of the type Stéréoflex or Multi- 
scope have the advantage over the use of recti- 
fied photograph on the stereosketchmaster. We 
consider the elements of orientation more ex- 
actly, and the working method is also shorter." 
The next paper on which I should like to 
comment is that of Mr McMillen. Mr McMillen 
gives a review of the applicability of the approx- 
imate instruments in the United States. He is, in 
fact, mainly talking about the American approx- 
imate instruments, the Stereographometer, the 
KEK, the Wernstedt-Mahan plotter, and the 
Multiscope. 
Mr McMillen states that application for 
transfer of interpretation data into maps is very 
good, and that the instruments also may be very 
good for map revision. However, he is not very 
much in favour of new map-making by approx- 
imate instruments, and I think it is useful that I 
read the conclusion of his paper also: “In 
summary, the limited application of third-order 
plotters seems to be a matter of simple econom- 
ics. The only sources of economy with these 
instruments are low first cost and the use of 
paper prints instead of glass-diapositives. Over 
a long period of use, these economics become 
insignificant in comparison to the losses arising 
from the lack of ability to produce a better 
product. The user soon finds that, by making a 
relatively small additional investment (that is, it 
is small when amortized over the life of an 
instrument) he can provide himself with an 
instrument which produces much more satis- 
factory results.” 
I should now like to say a few words about 
my own paper, only the last part of it. I have 
made there some suggestions for discussion. I 
should like to start with the first question for 
discussion, that is the definition which was also 
read out by Mr Vanderheyden a few moments 
ago, the definition of instruments belonging to 
this third order group of instruments. The defi- 
nition which we made at the meeting in Brussels 
in June 1959 was as follows: 
"Restitution instruments, offering the 
possibility of continuous tracing of the plani- 
metry and altimetry, but not based on a 
rigorous (that means geometric exact) recon- 
struction of the two perspective bundles of 
rays. 
| think that is a good definition but last 
night, looking over this dgain, I saw one dis- 
advantage. Here we have planimetry and alti- 
metry. You know the Radial Line Plotter, the 
KEK and the Hilger & Watts, do not allow 
altimetric plotting, but I think they belong to 
this group. Are there any suggestions here to 
change the redaction of this sentence so that 
tracing of the planimetry and altimetry is pos- 
sible? Shall we change that somehow? Are there 
any suggestions here or shall we leave it as it is? 
Mr M. VANDERHEYDEN: Instead of plani- 
metry and altimetry we could say, “planimetry 
and/or altimetry”. 
Mr H. C. ZORN: Thank you, that is a very 
good suggestion. We could also change it by just 
removing the word "plotting". 
Mr M. VANDERHEYDEN: That is another 
solution. 
Mr H. C. ZorN: Mr McMillen, have you any 
idea in this field?