521 
On the one hand it was obvious that the planning of the mine, the 
railway and the harbour must be based on aerial photography and 
mapping. On the other hand it was clear that the existing map of 
Liberia, i. e. the American aerial mosaic based on aerial photographs 
taken in 1952——53, could be used only for the first outlines. The lack 
of a vertical control system was a vital point. 
For time-saving reasons it was desirable, however, to start the plann 
ing by means of the already existing American aerial material. Thus, 
at the end of 1956 the first map of the Nimba Area was prepared by 
means of photographs delivered by the US Air Force in Washington. 
The vertical control points required were furnished by the Lamco 
geologists at Nimba by means of a barometric measurements. At the 
same time the staking of the railway line, made in Stockholm as an 
interpretation study, was pursued in a forced way. This preliminary 
proposal of the railway line required an up-to-date photography for 
Lamco. 
Thus, the first aerial photography was carried out in 1957 and the 
second one in 1960. 
In 1958, when it was decided that a more accurate mapping had to 
be carried out it was considered necessary to establish geodetic net 
works of such an order that an aerial mapping would give the accuracy 
needed even for the large-scale maps in question. 
According to these plans, a first order geodetic network, called the 
Nimba Geodetic Network, was planned including the total area of the 
Nimba Concession Area and surroundings. It was carried out as a 
trilateration in combination with a common triangulation. 
The network consisted of six (6) first order points and twenty- 
two (22) second order points. 
3.1 Connection of the Network 
The next step was to connect the local Nimba network with the offi 
cial map of Liberia, i. e. to the co-ordinate system of the American 
Aerial Mosaic. The primary reason for that was the requirement to get 
the mapping areas of Nimba and Buchanan locally connected with the 
surroundings for any measuring extended out of this area. It was also 
considered desirable to connect the areas due to the levelling system of 
the railway line. 
When the connection problem was scrutinized it proved to be a 
complicated task. 
It was obvious that only a few places identified on the American 
mosaics could be recognized on the Lamco photographs of 1957. Since 
the American aerial photography in 1952—53, taken from an altitude 
of 6,000 m, the changes have been so far-reaching that the larger towns 
only could be recognized on the photographs of 1957. 
From this point of view, the only features well defined in the both