6
the central projection. The analytic relations between variations of the
coordinates due to such disturbances in the adjustment of the lens-
system can be derived and can be inserted in the computations.
By changing the base setting from base in to base out, the instrument
will probably undergo small deformations. These deformations will of
course cause systematic errors in the reconstruction of the pencils of
rays. This fact is of special importance in aerial triangulation. The
effect of such disturbances can be avoided by using the "model triangu-
lation method" [5].
As mentioned, the value of the projector constant can be found when
the measuring procedure is repeated at two different projection distan-
ces. In this case the principal distance could be determined to be 99,888
mm. The standard error of this determination was 0.023 mm.
If high accuracy is wanted in the determination of points of photo-
grammetric models or aerial triangulation strips, the influence of the
systematic errors of the reproduced pencils of rays can numerically be
compensated. This problem has been treated in [6].
References
1. Hallert, B.: A New Method for the Determination of the Distortion and the
Inner Orientation of Cameras and Projectors. Photogrammetria XI 1954
—1955, 3.
— Fifth interim technical report. Basic Factors limiting the Accuracy of
to
Mapping and Aerotriangulation by Photogrammetric Procedures. 1. Jan.
1954 through 31 March 1954. Mapping and Charting Research Laboratory,
Ohio State University, Columbus, Ohio.
3. Rehnlund, E.: Determination of Some Systematic Deformations of the Pencils
of Rays of Photogrammetric Plotting Instruments. Fotogrammetriska
Meddelanden II/5. R. Inst. of Technology, Stockholm, 1956.
4. Hallert, B.: Some preliminary Results of the Determination of Radial Di-
stortion in Aerial Pictures (manuscript).
5. Ekelund, S.: Photogrammetric Triangulation with Separately Orientated Ste-
reo Models. Photogrammetria VIII 1951—1952. 4.
6. Hallert, B.: Über die Fehlertcorie der Aerotriangulation und einzelner Bild-
paare. Zeitschr. f. Verm.wesen 1955, 10 und 12.
