10 
For the revision of orthophotos the original profile plates 
have been used together with new aerial photography. A 
research programme has been initiated to facilitate a more 
flexible use of old height information. Colour orthophotos 
have been produced, 
Plotting instruments are checked periodically by grid 
measurements at three Z-levels. The standard error or unit 
weight in the image scale has during the period varied from 
4 to T micrometers for precision plotters. 
5 COMMISSION III Mathematical analysis of data 
Aerial triangulation and block adjustment have been used 
in Sweden for small scale mapping for a long period. Speci- 
fications for large scale mapping have been based on regula- 
tions formulated by the former Land Survey Board (now ) 
National Land Survey). These specifications have, however, 
now been replaced by recommendations prepared by the National 
Land Survey. The recommendations are written in such a way 
that more concern is given to the final result than to the 
methods used. This gives the map producer more freedom in the 
choice of methods. The use of aerial triangulation is, 
accordingly now widespread in Sweden also for large scale 
mapping. 
Measurements for aerial triangulation are mainly made in 
analog instruments but two stereo comparators are also 
used in production. 
Photogrammetric block adjustment in Sweden is up to the 
present time only carried out using the independent model 
method. New programmes have been developed during the last 
four years. Some of these programmes allow for correction 
for earth curvature, refraction, affine film shrinkage 
and for individual camera distorsion as well as for compu- 
tation of orientation data for the separate stereo models. 
At the Royal Institute of Technology Urho Rauhala became 
Technical Doctor in 1974 presenting his doctorial thesis 
"Array Algebra with Applications in Photogrammetry and 
Geodesy". The thesis deals with the use of matrix arrays 
for interpolation and adjustment.