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I:
PRESENTATION OF THE GENERAL REPORT OF SUB-COMM IV-3 159
eine nähere Beschreibung, Charakterisierung
dieses Gebietes; das liegt in Renfrew, in Kanada,
und die Bearbeiter waren von der ganzen Welt.
Die kannten dieses Gebiet überhaupt nicht, und
es wäre sehr wichtig gewesen, wie ich das jetzt
ganz kurz gesagt habe, diese Gegend etwas zu
charakterisieren, besonders auch hinsichtlich
des Waldes, der ja zum Teil etwas Schwierig-
keiten bereitete, wie und ob man den wieder-
geben soll. Dann auch die Landnutzung, das
ist eine landwirtschaftliche Nutzung aber sehr
typischer Art, und es wäre sehr interessant ge-
wesen und hätte einem auch manchen Fehler
erspart, wenn man da etwas Näheres gehört
hätte. Und dann auch noch ein Hinweis darauf,
was man in einer Auswertung erster Ordnung,
und was man in einer Auswertung zweiter Ord-
nung bringen soll. In einer Auswertung zweiter
Ordnung wird man Verschiedenes weglassen
können, aber was kann und soll man weglassen,
was würde einem nicht als Fehler angerechnet.
Also das wäre auch ganz wichtig gewesen. Und
ich möchte nun schliessen, weil die Zeit schon
sehr fortgeschritten ist, noch mit einer An-
regung.
Sie haben gesehen, ich habe hier das Bild
etwas charakterisiert und sagen wir, vielleicht
eine Art Interpretation dieser Landschaft ge-
geben aber nicht eine solche, wie sie in der
Kommission VII angewendet wird, sondern im
Hinblick auf unsere topographischen Zwecke
und Notwendigkeiten. Und ich glaube, man soll-
te da einen Abschnitt wenigstens bringen in
einem Buch über Photo-Interpretation, und wir
sollten uns überlegen, was wir von einer solchen
Photo-Interpretation für topographische Zwecke
für Nutzen haben. — Also damit darf ich schlies-
sen. Ich danke sehr.
Continuation of the Presentation of the General Report
in the Meeting held on Thursday, 15th September, 1960
by the President, Mr Blachut
I have had occasion already to present the
results of our experimental work, and we should
start the discussion. I do not know if there are
any questions or not, but maybe it would be
practical just to refresh your memories a little
as to the most important results so that I shall
not repeat what we did but will just quote the
conclusions reached from the experimental
work, and describe why we reached such con-
clusions. Of course, if there were to be any
questions and discussion it would be very nice.
As you will remember, the experimental
work has been carried out on a single stereo-
plotter flown over the test area which was estab-
lished for this particular purpose. I should like
to add that as far as the scope of the experiment-
ing is concerned, it was a decision of the special
meeting in Brussels. There may be different
points of view as to whether we did right or not,
personally I think it was an excellent idea that
we decided to limit the scope of our experi-
mental work. As you will remember, four years
ago we had much larger projects and so we left
it to our participants to choose the type of pho-
tographs, equipment, scales, ground control, and
so on. As a result, it was extremely difficult to
reach any conclusion.
This time, because we have used exactly the
same — one stereoplotter and each participant
used identical ground control points — all the
information was identical and it was much easier
to reach certain conclusions.
These conclusions are as follows: the most
serious elevation errors encountered in photo-
grammetric mapping seem to have their origin
in corrected procedures rather than in photo-
graphic material. That is a very important re-
cognition, and it is exceedingly encouraging. It
proves that present photogrammetric equipment
is of very high quality, and if the user of the
photogrammetric material and equipment pro-
ceeds properly we may be sure that the results
will be very good.
Of course, we have been using a single pho-
tograph to start with, which is not a large statis-
tical piece of material, so to speak. However, we
produced in addition about 25 independent
stereo-opers over exactly the same test area and
we tested at the National Research Council all
the stereo-opers in order to find out whether
photographs made in entirety in day and under
different conditions are of the same quality or
not, and we could not find any large deviations.
The second conclusion is that unfortunately
so far there have not been any devices which
would permit of correction for earth curvature
in small-scale mapping. That is obviously one
source of error, and I think it is one of the
results of such investigations that the manufac-
turers of the equipment pay more attention to
our requirements.
Again, I think the next conclusion is quite
novel and very important: that human factors
are greatly responsible for appreciable errors
which may have a systematic error. We analysed
this question and there are surprising results.
TY
dee —