ie 
aa 
si psc dte 
te te ts 
     
     
  
  
  
  
    
   
    
  
    
    
   
   
  
  
  
Hem ls en ipi 
  
  
    
(6) 
The limits ot the precision of the Stereotop are defined by the 
accuracy of representation of the height error by the equation of the 
hyperboloid. 
z= a.X + b.y + C. xy. 
Its limitations become evident when we realize tha 
nomial expression of X which can not be accomodate 
is so influential that errors of the order of 1/300 for one degree tilt can 
occur. Even if the range of x is split up in the middle the maximum 
error due to one degree of tip is still about 1/1300 in flat country. 
t the part of the poly- 
d in such an expression 
The design of the correcting mechanism of the cartographic Stereo- 
micrometer is based on the property that the hyperbolic paraboloid is a 
ruled surface. The surface is physically formed near the instrument. 
A feeler moves on the surface and communicates the correction corresponding 
to its position. This mode of generation of the correction does not permit 
the attainment of the high intrinsic precision of the principle. 
Hyperbolic paraboloidal corrections to the parallax are also included 
in the Soviet precision stereometres by the mechanical realization of the 
individual terms of the first order differential of the parallax. The adopted 
solution makes rather heavy demands on the manufacturing precision, and 
it is difficult to see how they can possibly cope with the case of mountainous 
regions. 
5. Prospects of a new Series of Plotting Instruments Derivin I 
from the Polynomial Representation of the Scale Parameter. 
It appears from the previous discussion that the field of stereoplotting 
instruments based on analytical approximation rather than the geometrical 
solutions remain to be fully explored. 
A moment's reflection will show the principal advantage of setting 
out with the generation of the scale parameter to the high degree of 
precision attainable by the polynomial representation. For, with the scale 
parameter correctly evaluated for each point, the determination of the ground 
coordinates becomes simple linear transformations. 
The automatic generation of X as a continuous function of x and 
y in the commendable form is best done mechanically. It can in fact be 
shown that the afore- mentioned precision is attainable by simple means