15 
rate and complete information about the systematic disturbances than 
the y-parallax method. The latter method is particularly limited by the 
considerable correlation between the two pictures. There may be distor- 
tion effects in the two pictures that cannot be distinguished from each 
other in this way. 
None of the two methods can give any absolute determination of the 
elements of the inner orientation under here assumed conditions. 
In fig. 11 the results of an investigation of a lens for non-topogra- 
phic photogrammetric purposes are presented. In this case also absolute 
determinations of the inner orientation are easy to perform. 
Summary 
The two methods for the determination of the radial distortion in 
aerial pictures, the grid method and the parallax method, ought to be of 
considerable practical interest. The distortion correction device in plot- 
ting instruments should be constructed with respect to the real distor- 
tion in the air. Asymmetries and other disturbances of the pencils of 
rays must be determined under real photography conditions. These are 
important conditions for the development of photogrammetry. 
References 
l. Schwidefsky, K.: Grundriss des Photogrammetrie. Fifth edition. Stuttgart 1954. 
Page 211. 
2. Hallert, B.: Über die Herstellung photogrammetrischer Pláne. Diss. Stockholm 
1944. 
3. Hallert, B.: Contribution to Theory of Errors for Double Point Intersection in 
Space. Transactions of the R. Institute of Technology. Stockholm 1950. 
No. 35. 
. Hallert, B.: Some Preliminary Results of the Determination of Radial Distor- 
A 
tion in Aerial Pictures. Photogrammetric Engineering. 1956 Number 1. 
(March.) 
». Hallert, B.: A New Method for the Determination of the Distortion and the 
Inner Orientation of Cameras and Projectors. Photoerammetria, 1954— 
1955, 3. 
0. Hallert, B.: Uber die Fehlertheorie der Aerotriangulation und einzelner Bild- 
paare. Zeitschrift fiir Vermessungswesen. 1955. 10, 12. 
. Leijonhufvud, A.: On Astronomic, Photogrammetric and Trigonometric Re- 
fraction. Diss. Stockholm 1950. 
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