Sweden 11 
The establishment of Airborne Mapping Ltd may be regarded as a 
consequence of the need of up to date accurate maps for prospecting 
and forestry activities. 
Twin motor aircrafts of the type Airspeed Oxford, suitable for 
prospecting, were procured for the air photography. At first the navi 
gator was often a photographer with some knowledge at navigation, but 
nowadays the company lays great stress on his navigational training. 
The cameras used are Wild Aviogon, 9" X 9", and Aviotar, 18 X 18 
cm. 
The company has one Zeiss rectifier SEG V and one Zeiss Radial- 
secator RS 1 as well as simpler stereoscopic instruments, and intends 
to procure more elaborate instruments soon. 
Kjessler and Mannerstrale Consulting Engineers 
Kjessler and Mannerstrale is a consulting engineering firm specializ 
ing mainly on road, street, bridge, factory, water and sewage engineer 
ing designs together with town-planning and architecture. The num 
ber of employees is about 180. 
This firm has for a long time had a mapping section of its own to 
supply the other departments with any maps they may require besides 
accepting mapping commissions. The company has for many years been 
using hired instruments for these purposes, but in 1955 it purchased a 
Wild Autograph A 7. 
Most of this work is applied to drawing large scale maps for project 
ing roads and for reconnaissances of possible alternative routes direct 
ly in the stereo-models. Photo-interpretation and profile measurements 
are essential parts of the latter. The photos are ordered from the Geo 
graphical Survey Office. 
Research and Developments 
Since the Geographical Survey Office began to renew its camera 
equipment in 1952 it has been very urgent to test the new cameras, 
which has been done in several ways. They were first tested by photo 
graphing test-tables from the air to determine their resolving power. 
The results have been partly published by Welander [65]. To determine 
the total distortion there were also taken photographs of plane ice sur 
faces. A distortion curve was computed from the height errors of a 
stereo model. This empirical curve differed remarkable from a corres 
ponding laboratorial curve only contenting optical distortion. After 
computing the distortion effect of the earth curvature, of refraction and 
of errors of the pressure plate, the superimposing of their curves on the 
laboratorial distortion curve gave an expression to the total distortion, 
apparently agreeing with the empirical distortion attained from the ice 
pictures.