cameras and theodolites and experiencing the unreliability of photogrammetric materials, knowing 
the metrical advantages of long focal length, narrow angle photography but constrained to use 
other cameras in architectural photogrammetry, has provoked these proposals on photographic 
procedures to allow analytical reduction of radial error in wide-angle, close-range photogrammetry 
which are illustrated in Figures 9 and 10, 
  
Figure 9, Principle of determination of point location in object space from the intersection of narrow segments of 
three planes, one from each of three camera stations employed in analytical photogrammetry. 
In Figure 9 three camera stations are used. Point determinations in object space are not 
on the basis of the adjusted best intersection of three lines of sight but on the basis of the 
intersection of narrow segments of three planes, one from each camera station, Each plane is 
determined by the intersection of the camera axis with the line extending outwards from the 
principal point in the image plane to the image of the point. Measurement of the angle of this 
radialline is from the camera horizon marked in object space and recorded in the image plane. 
Figure 10 illustrates the principle for determining the ray - or line of sight - to a point 
in object space from a single camera station from which the point has been photographed along 
two divergent camera axes. The similarity to the procedure for elimination of radial error in the 
measurement of building movements can be noted. The calculation of the intersection of the planes 
should include the actual small displacement of the exterior principal point of the camera lens, 
caused by change of camera axis. 
In cases illustrated in both Figures 9 and 10 in which the camera must be tilted upwards 
for coverage of a tall building, photographs should first be taken with a horizontal camera axis. 
Then the vertical line between the principal points in the level image plane and the inclined image \ | 
plane is the basis for measurement of the angles of the radial lines to image points in the inclined ) UN 
image plane, The inclined image improves the intersection of planes and determination of points 
near the control in the camera horizon. 
—1t6—