kind by untiring technical and human efforts and to make in-
ternational friends by using the possibilities of modern
times in which to live he considered a great privilege.
Karl Lofstrom was certainly a unique and great personality,
unforgettable to all who met him. I also had the personal
privilege to have known him for quite some time. The open
and uncomplicated friendship which he extended touched me
deeply. He was the kind of person one meets only very rare-
ly in life and whose memory one cherishes deeply.
I am therefore very happy and consider it a great privilege
and honour to deliver this lecture in his memory. It is
more than a coincidence that the topic deals with auxiliary
data in aerial triangulation. This topic had Karl Lofstrom's
attention throughout his life. I recall vividly his enthu-
siastic interest in the recent results of statoscope trian-
gulation. I consider it a dutiful reverence to Karl Lófstróm
to deploy here the development of auxiliary data and to show
that they will soon have much greater impact on photogram-
metry than he could have anticipated.
2. AUXILIARY CAMERA ORIENTATION DATA IN THE PAST
2.1 The indirect restauration of the orientation of aerial
photographs - known as the fundamental problem in aerial
surveys according to Seb. Finsterwalder - has governed the
working methods of photogrammetry for more than 60 years.
Modern aerial triangulation is only the latest highly
effective step in solving this problem. It is not surprising,
therefore, that there have been many attempts to measure at
least some orientation elements directly during the photo-
flight.
Statoscope and horizon camera (Nenonen, Väisälä, Lofstrom)
originated and were first applied in Finland for photo-
mapping by rectification. The instruments provided, with
scale differences and tilt, the most essential orientation
elements of aerial photographs, allowing rectification
without much control. Soon also the use of statoscope and
horizon camera for spatial strip triangulation was developed.
We recall the method of aerolevelling in which bz, w and ¢
values of photographs were set directly in the triangulation
instrument, after correction for the reference system by
ground control in the first and last model of a strip, /2/.
Particularly statoscope data were effective, as they control
the second summation of the transfer errors of model
connections.
Other camera manufacturers pursued quite early similar ideas
of deriving camera orientation data. We recall briefly
Santoni's solar periscope and Nistri's early attempts to
attach gyroscopes to the camera body for measuring attitude
data, /3/.
It is remarkable how the early pioneers of aerial photogram-
metry conceived quite modern ideas of measuring camera
orientation data directly, although the methods were prema-
ture and had limited success.
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