4. FINLAND 
NATIONAL REPORT OF THE FINNISH SOCIETY 
OF PHOTOGRAMMETRY. 
All the redressing of air pictures in Finland is based on known an- 
gles of tilt measured from horizon pictures, the scale being determined 
by control points or check lines. All mosaics are assembled using the wet 
process. 
A) MAPS ON SCALE 1:25 000 AND MINOR SCALES. 
a) Most of them have been done by redressing of single photographs 
assembled to controlled mosaics, the final map scale being 1:100 000. 
Only a few works have been obtained by restitution of couples of stereo- 
scopic plates in Aero-Multiplex, the final map scale being 1:50 000. 
b) The restitution has been executed on scale 1:10 000 and the 
redressing on scale 1:20 000, which are the drawing scales. Both of the 
final maps are trasformed by reproduction camera to the final map scale. 
c) The equidistance of the contour lines is 10 m (in stereoscopic 
works only). 
d) The maps are based on fixed points obtained by triangulation 
or measuring of traverse and completed by mecanical or stereoscopic 
triangulations when necessary. 
e) The accuracy obtained depends on the amount of fixed points 
(about + 15 m in position for the scale 1:100 000 and + 5 m in height 
for stereoscopic works, (Gaussian mean error). 
f) The former are used as economical general maps and the latter 
as special maps in forestry. 
g) Pre-existant economical maps 1:100 000 are put up to date 
with the help of redressed single photographs or controlled mosaics. 
22 —