old ones in many cases. When the question of the acquisition of new maps 
became urgent, photogrammetrical methods were tried in the past 8—10 
years. A characteristic of their methods is — contrary to the methods 
employed in the State forests — the attempt to replace drawn maps by 
aerial photos. The most important of these methods have been developed 
by the companies named below, all situated in Norrland. 
Svenska Cellulosa AB (Swedish Pulp Co.) 
Chief Forester District of Sundsvall (see map fig. 3) 
The area of the district is almost 7 000 sq. km. The photo project in the 
summer of 1949 had to cover 20 000 sq. km because of the dispersion of 
the company’s woodland lots. Management of the forests is carried out 
with a system of big units, often tens of hectares in size, so that maps do 
not have such significance. Forest maps have been lacking altogether or 
what there were dated at least 30 years back. In these circumstances, many 
rangers have acquired the habit of getting along without any maps at all. 
In 1948, however, the company decided that new maps should be made 
without delay. In view of the time factor as also the question of expense, 
the decision was in favor of aerial photos, though a special contract had 
to be made with the Geographical Survey Office for the photos. Photos 
were made to meet the standards stated earlier, on the scale of 1: 20 000. 
Compared with standards of today, the quality was not too good. 
Owing to the urgent need for maps, contact prints were supplied to 
district foresters and rangers without delay, complete with pocket stereo- 
scopes and plastic folders. As the size of the prints, 30:30 cm, caused dif- 
ficulty for stereovision, the stereoscope was equipped with leg supports of 
special design (Simonsson patent), which conveniently fold the edges 
of the photos (fig. 4). In addition, the forest districts were supplied with 
mirror stereoscopes of Nife and Deift type. No special training was given 
in photo interpretation, and each ranger was left to use the photos as he 
thought fit. Nothing but a short instruction in the use of photos was given 
and the stereo-vision was checked. This daring experiment seems to have 
turned out a success. To begin with, the aerial photos were used mainly 
by foresters, but as the years went by most forest rangers became keen 
photo interpreters and have managed well by using aerial photos instead 
of maps, particularly for orientation in the forests and for projection of 
operations. 
However, the map material the company required was of bigger size, 
true to scale and with no photo overlap, which was to be finished by draw- 
ing in some details. This material was intended for use indoors. Before the 
aerial photography was put in hand a good many controls were marked 
on the ground, but many of these did not appear on the photos because of 
shade, overshadow or poor contrast. Nevertheless they furnished an ade- 
quate basis for a mechanical photo triangulation performed by B. H a I- 
lert and P. O. Fagerholm. The photos were subsequently rectified 
to the scale 1: 20 000 and were assembled as mosaics in sections of 50X50 
cm. It is true that errors along the lines of junction amounted to 2—3 mm, 
but this has not materially diminished the usefulness of the mosaics. In 
order to get the most out of these mosaics replacing forest maps, they were 
8 
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