PHOTOGRAMMETRIC ENGINEERING 
graphs, a better knowledge can be obtained 
about their occurrence and distribution. 
Based upon this information steps can be 
taken to create possible reservations as a pro- 
tection against extinction. In addition to this 
the department dealing with this subject has 
also used aerial photographs to study the dis- 
tribution and movement of seals and rabbits. 
PORTUGAL 
Based upon the study of aerial photographs 
an Agricultural and Forestry Map in separate 
sheets of the whole country has been pre- 
pared on a scale of 1:25,000. Map compila- 
tion was achieved by transferring agricultural 
and forestry features, interpreted and de- 
lineated on the photographs, to the map. For 
this purpose the military map of Portugal 
(scale 1:25,000) served as a base. The origi- 
nal photographic scale was 1:32,000; occa- 
sionally also photographs on a scale of 
1:16,000 were taken. The results of this gen- 
eral survey revealed interesting information 
regarding the local occurrence of the fig tree, 
the olive tree, the Mediterranean pine, the 
Eucalyptus tree and the Cork oak. 
The total area studied by aerial photo- 
graphs amounts to 89,000 sq. km. This study 
was based partly upon aerial photographs and 
partly upon observations made during the 
feld work. The application of aerial photo- 
graphs achieved a saving in time of about 
10095 compared to conventional terrestrial 
methods. 
SWEDEN 
During the years 1957-1959 approxi- 
mately 2 of the forest area of Sweden (or abt. 
367,000 sq. km) was photographed. In addi- 
tion, the whole country has been photo- 
graphed from an altitude of 10,000 m. Most 
of the photography has been carried out by 
the Geographical Survey Office for the pro- 
duction of the public maps, and only a 
smaller part has been photographed specially 
for forestry purposes. But photographs from 
all these surveys can be utilized for forestry 
purposes. 
The camera used is Wild RC Sa, 23X23 
cm, Aviogon (6 inch). The photography from 
an altitude of 10,000 m has been done with 
the camera Eagle Mk II, 23X23 cm, Ross 
6". 
The negative scale is normally between 
1:20,000 and 1:30,000. As a rule panchro- 
matic film is used, but for experiments, modi- 
fied orthochromatic film and color film have 
also been used. 
[n all parts of the country aerial photo- 
12 
graphs are used for making forest maps. N w- 
adays almost all forestry mapping is based on 
photographs because field work has become 
too expensive. 
There are forestry maps of different kinds 
and they are used mainly for orientation in 
the forest, the general view of forest blocks, 
for the planning of several operations and for 
registering completed work. Both drawn 
maps and photo maps are used. The drawn 
maps are generally made in a simple way. 
Stand boundaries and other mapping details 
are sketched by stereovision on one print of a 
stereo-pair at a scale of about 1:20,000. Then 
with the aid of a projection instrument (optic 
pantograph) the map details are transfused 
directly from the prints to drawing film, 
where the property boundaries and other 
fitting points as roads, buildings etc. are 
plotted at a scale of 1:10,000. 
Photo maps of different types are used. 
Normally stand boundaries are not marked 
on photo maps. During the last few years the 
use of more simple photo maps has increased. 
Mosaics are not so popular owing to costs and 
defects in the points. Instead enlargements 
from a single negative are used as maps. This 
can be done when the photographs have been 
taken from a relatively high altitude. 
In the southern part of Sweden forest maps 
generally have a scale of 1:10,000, and in the 
northern parts 1:20,000. 
Photographs taken from an altitude of 
10,000 m (scale 1:65,000) have also been 
used for preparing maps. From these photo- 
graphs compilation maps can be plotted by 
plotting machines (A 8) at a scale of 1:10,000, 
and this plotting can be done at a low cost be- 
cause every photograph covers a large area. 
Enlargements to the scale of 1:20,000 are 
also used as photo maps. On the photos taken 
from 10,000 m, the displacements of details 
owing to central projection are essentially 
smaller than on those taken from a lower alti 
tude. Naturally the photos taken from a high 
altitude are not suitable for forest interpreta 
tion, but they give a good general view of the 
topography and of forest and non forest-land. 
For many purposes it is suitable to use ex 
tremely small scale photos and photos at nor 
mal scale (1:20,000-1:30,000) in combina- 
tion. 
[n addition to mapping, aerial photographs 
are more and more used for forest interpreta- 
tion purposes. Thus information necessary 
for planning several forest operations can be 
acquired. The use of aerial photos saves much 
field work and at the same time the photos 
give a better view of several conditions in the