comparator with the horizon line in nearly vertical position. The other images were one by 
one fixed in the same position in the right frame. On stereoscopical examination the relative 
displacements - now apperaring as horizontal parallaxes - of the horizon line and the 
fiducial marks in three points - in the middle and on the both ends of the horizon line - 
were measured with the floating mark. - The reading accuracy of the parallaxes is about 
+ 2 y, the distance between the remotest fiducial marks in the horizon image 22.0 mm and 
the P a length of the horizon lenses is f= 34.2 mm. 
The accuracy of the obtained relative inclinations of the consecutive photographs was 
greater than expected. The mean value of the inclinations measured and calculated 
independently from the left and right horizon images has a standard error of + 1.37. This in 
oie of the fact, that the right horizon line is considerably, less distingt compared with 
the left one. Consequently the accuracy of the relative inclinations determined only from 
the left horizon image might stil be greater. 
The accuracy of the Horizon Controlled Angular Orientation was tested by means of the 
elements of the absolute external orientation determined in the autograph A7. 
The relative horizon inclinations were transformed into absolute ones using absolute values 
of ¥ and w (reduced on the image coordinate axes of the main camera ) of two models, 
one at the beginning and one at the end of the plotted strip. Thus obtained absolute 
inclination values of the whole strip were compared with the actual ones. 
The deviations from the actual values gave the following standard errors for the absolute 
inclinations, calculated from the horizon measurement: 
  
mu m 
The whole strip NR 613-632 
Monocular horizon measurement tos + 4.4° 
Stereoscopical horizon measurement + 3.5% + 3.2 
1. Half strip NR 613-623 c e 
Stereoscopical measurement t 4.5 * 2.8 
2. Half strip NR 622-632 e c 
Stereoscopical measurement * 1.8 + 3.0 
The time has been to short for detailled study of the results and there are some systematic 
and "gross" deviations { until 7” } that must be througly analysed. The absolute orientation 
in the autograph was not quite satisfactory and especially the Ÿ values are not fully 
reliable. 
The increased accuracy obtained with the new horizon camera compared with earlier 
results might be due to following facts: 
- the optical quality of the lenses and the used filters give a sharper and clearer 
image of the horizon, 
the four horizon images make it possible to choos the best ones for the measurement and 
eventually to use the mean value of two independent measurements. 
  
/ Y / K. G. Lefstróm: LATEST DEVELOPMENT IN THE DIRECT DETERMINATION OF THE 
OUTER ORIENTATION. International Archives of Photogrammetry 
1948 VOLYM X Second Port, page ( 246 ). 
  
  
  
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