interval was made on photogrammetric basis over the Abisko region. 
A touringmap of Gotland 1:200 000 without contours was made 
with the Economic Map as basis. 
k) Maps for other purposes. 
I. The State-Railways has drawn about 40 plans of railway stations 
on the basis of redtoned, rectified single pictures 1:1000. 
II. In 1951 civil engineer Stig Thorén made an interesting experi- 
ment of periodical mapping of gravel-pits and determined the amount 
of gravel removed during a certain period. The gravel-pit and some si- 
gnalled passpoints around it were photographed from a helicopter for two. 
Surveyingcamera Kagle 20,12 x 12 for film was used, and the ste- 
reoplotting was made in a Wild A 5. Negative scale about 1:7000 and 
map scale 1:400. Interval for contours 1 meter. Because of the land-slide 
risk the gravel-pit could not be mapped according to classical methods. 
The vibrations of the helicopter unfortunately caused unsharpness in 
several photographs. At the plotting in the stereoinstrument it was im- 
possible to orientate one of the models because of a « dangerous surface ». 
In comparison with classical mapping this method was rapid and econo- 
mical. 
III. Engineer Thorén and the Finnish engineer, now Doctor of Tech- 
nology, Halonen have also made certain terrestrial photogrammetric 
mapping in connection with the projecting of an oil-store in an old mine. 
The purpose was on one hand to map the opening of the mine for 
the projecting of a bed to a concrete roof, on the otherhand to determine 
the thickness of the rockroof in one of the larger minechambers. The 
first task was solved with Zeiss phototheodolite. The photographs were 
taken according to the normal case, and the plotting was made in a 
Wild A 6. The other task was solved with Wild's stereoscopic camera. 
Photographs were taken inside the mine, with several nadir distances, 
and on top of the roof of the mine-chamber. The plotting was made 
in a stereocomparator. Through ground-sounding on the roof of the mine- 
chamber the thickness of the loose earth-layers were determined, after 
which the dimensions of the mine-chamberroof could be decided. 
IV. In 1949 Engineer Thorén and professor Hallert at the Royal 
Institute of Technology mapped photogrammetrically a number of 
coal-hills to determine their volume. A phototheodolitd was placed in a 
crane, hich was moved to a suitable position so that the desired stereo- 
scopic covering was obtained and so that the signalled passpoints should 
fall on the photographs. The determination of the volume according to 
this method appeared to be very exact. The form of the base-surface 
must however be very well known to avoid systematic errors. 
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