MEN Aa AD 1e 
UJ 
CD ^" — 
m SS 
to be triangulated and drawn in the instruments Wild A 7 respectively 
A 6 using the American pictures. 
Having finished the aerial photography in 1957—58, I had to carry 
out a base map of the Nimba Region at the scale of 1:5 000 which 
was established in the Wild A 8. A geodetic net of the Nimba Region, 
carried out by another group in the years 1958—59, has made it poss- 
ible to adjust this base map due to the scale and the tilt. This map 
is drawn as a second edition.?) 
In 1959, a geodetic group had to carry out a field survey comprising 
control points within the Community Areas of the Nimba Area. The 
map plotting in the Wild A 8, with the aim to draw a detail map at the 
scale of 1:2 000, is now going on. An analogous map of the Buchanan 
Area has been executed earlier.*) 
In addition to that a band-shaped map along the railroad line from 
Buchanan to Nimba has been carried out in the Multiplex plotter as 
controlled mosaics at the scale of 1:10 000.5) 
3. Photogrammetrical treatment 
The following section deals with the principal theme of this paper. 
Before then, I should like to call the attention to some basic points 
concerning the lens distortion and the camera calibration, which in the 
professional discussions have faced most divergent opinions. In fact, it 
should be highly appreciated if the IX. International Congress could 
contribute to purify the technical flora in this field [12]. 
In that question I should like to state some views of my own, as 
follows: 
l. The determination of the lens distortion curve and the calibration 
of the photogrammetric cameras manufactured by companies, known 
to all the world, must be considered as reliable when delivered — until 
something happens that will prove the contrary. 
2. Up till now, the continous control has been carried out as a) exa- 
minations in the laboratory, b) theoretical investigations or c) practical 
tests viz. 
a) in the laboratory by the manufacturer again or by the user him- 
self, 
b) as a mathematical treatment in a way of calculation of the single 
picture or of the stereoscopical model, the latter method known 
as "the y-parallax method" [6—10]. 
C) by means of tests in practice, e. g. by using astronomical methods, 
tests fields or ice-covered lakes etc. [3]. 
3) The group, under the author's management, consisted of Messr. R. Källbrink, 
T. Källbrink, Smith, Strömgren and Äkerblom. 
^) The group, under the author’s management, consisted of Messr. T. Käll- 
brink and Nilsson. 
5) The stereo-instruments belong to the Geographical Survey Office and to 
Sentab (LAMCO).