The Geographical Survey Office and the Land Survey Board have in 
collaboration with the Photogrammetric Division at the Institute of 
Technology arranged a camera-testing field on the island of Öland. The 
field is constructed according to the instructions of Professor Bertil 
Hallert, so as to be most useful for the determination of the systematic 
errors of the cameras. The first pictures of this field are now being 
measured. 
Different makes of films and combinations of films and filters, have 
been tried by the Geographical Survey Office with a view to ascertain 
ing the best method of photographing from the air, so as to facilitate 
photo-interpretation of details of special interest to forestry. Photo 
graphs have thus been taken with panero-, ortho-, infrared and colour 
films, and specially made filters have also been used. 
Guided by the results obtained in studying the resolving power of 
the new cameras the Geographical Survey Office has tried to increase 
the flight altitudes from 3 900 to 5 100 m in its routine works. The 
pictures taken from this greater height have with respect to resolution 
proved well suitable for the production of the Photo-Map of Sweden, 
too, and to far the greater height has caused no inconvenience to the 
subsequent work on the map in the Office. The time taken to produce 
the Photo-Map has on the other hand been considerably shortened. The 
number of models to be adapted by stereo-operation, for instance, is 
only half that previously required. 
The air photogrammetric researches of the Photogrammetric Divi 
sion of the Institute of Technology in Stockholm have in particular 
been devoted to the accuracy-limiting factors. See Hallert [69], [73], 
[75] and [78]. These researches have accordingly been concentrated 
upon finding some method of differentiating systematic from random 
errors. The photogrammetric process has therefore been studied syste 
matically in detail. A method of determining systematic deformations of 
the photogrammetric bundle of rays, when photographs are taken, has 
been found, as well as a similar method of determining the systematic 
errors in different types of stereoscopic instruments in reproducing the 
corresponding bundle. The co-ordination of the several photogrammet 
ric moments in the adaptation of single pairs of pictures up to the aerial 
triangulation has been studied. Special attention has been paid to the 
propagation of systematic and random errors from one moment in the 
adaption to the next. Equations have been drawn up expressing the 
accuracy of single and aerially triangulated models. 
The development work of the Rural Survey Organization has aimed 
at determining the accuracy, economy, and possibilities from a practi 
cal point of view of the photogrammetric methods. The accuracy of 
stereo-operations in a Wild A 8 on negatives from a Wild Aviotar 
camera has thus been investigated. This examination gave a ratio of