4 
mation point C. Here arises an error ö of the true position of the point m, on the ray Sm. 
The value of à = x", — x, can be with a high degree of accuracy obtained from the equation. 
x X 
Ó — e: a (1) 
Therefore, if the point m can be plotted by means of an ordinary spatial lever system, 
then the point m/ on the photograph will be got with aid of a secondary lever system con- 
  
nected with the former by a linkage to 
actuate an additional displacement of 
the photograph on the value ó, ac- 
cording to the equation (1). 
Fig. 4 represents the Stereoprojec- 
tor SPR-2 designed by G. V. Romanov- 
sky. In the lower part of this instru- 
ment is arranged a drawing board on 
Which the map is compiled. Above the 
board are disposed the three carriages 
X, Y,Z.On the carriage Z are set the 
base components b,, b,, kb,. Precise 
levers rotate about the projection 
centers S,, S5; with their lower ends 
the levers are coupled with the gimbal 
systems kb. and b,; with their upper 
ends they are coupled with the gimbal 
systems of the carriages of the photo- 
graphs arranged horizontally. 
The ratio of distance from the 
  
projection centers to photographs, and 
those to the base components, deter- 
mines the model scale, which can be 
changed from 0.5 to 2 as compared with 
the scale of the photographs. By 
changing these distances it is also pos- 
sible to fix the coefficient of stereo- 
model transformation, which coefficient 
remains invariable all the time the plot- 
ting is performed. The vertical dis- 
Fig. 4. placement of the carriage Z gives the 
contour interval of the stereomodel. 
In Fig. 5 is illustrated the scheme of the transformation of directions. Here are: 
1. 
2 
ce 
3, 4 
a vertical line; 
a lever for making resection, connected through a linkage with the carriage of the 
photograph, the orientation elements of which photograph are x, and Ax fia; 
the ends of the supplementary levers, arranged on the picture-carriages; the ends 
Ax 
of the said levers are set on the values of the “decentrations” 5 in order to 
bring these ends to the zero warping point. 
The right-hand supplemental lever carries a platform 5; in the process of orientation, 
the pushing device 6 is set on the value da in relation to the center of the said platform. 
Therefore at the inclination of the system 4-5 a lowering (or raising) of the support car-