coordinates, determined through partial and complete 
calibrations, together with other data, for classification 
purposes of stereoscopic projection instruments. 
8. Practical experience has indicated that repeated 
partial and complete calibrations of restitution instruments 
at suitable intervals are of great value for the reliability of 
the photogrammetric procedures. 
9. A new device for continuous, automatic testing of 
personal stereoscopic acuity has been found to be pro 
mising for the selection of operators and for the study of 
possible variations of stereoscopic acuity in connection 
with work in practice. 
10. It is for evident reasons desirable that the funda 
mental operations of photogrammetry be carefullv in 
vestigated in connection with experimental projects in 
photogrammetry and that the final results of such experi 
ments be judged with respect to the determined basic 
qualities of photographs, instruments and operators. 
11. This is the third and final report on investigations of 
fundamental problems in photogrammetry. The two 
previous reports were presented at the congresses in Lon 
don 1960 and Lisbon 1964.