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5. Determination of the most effective relation between 
flying altitude h and triangulation distance S 
We assume that an aerial triangulation is to be performed between 
control points at a distance of S. The most suitable flying altitude 
shall first be determined. It is evident that too low an altitude will 
require too many photographs and models to cover the distance S and 
that consequently the error accumulation in the triangulation procedure 
will become unfavourable. On the other hand, flying at too high an 
altitude will give too small a scale in the photographs and consequently 
too strong an enlargement of the inevitable errors in the photographs 
and measurements. 
There must evidently exist a certain flying altitude which will allow 
the aerial triangulation to be performed with a maximum of accuracy 
or a minimum of the standard errors of the final coordinates. 
Here we will determine the relation between flying altitude and 
triangulation distance which makes the radial standard error of the 
n 
coordinates in the middle of the strip | p =] a minimum. We will 
distinguish between the three different types of aerial triangulation 
which were treated above. 
5.1. Stereo-radial triangulation 
n 
For p = - we find from (351) 
h / n ; : 
m, — 8. — [54 (6 n? + 132) (354) 
For the triangulation distance S and the average base length b the 
number of bases n will become approximately 
S 
n (355) 
b 
Further, for the base-height ratio ó we have the relation 
b = h (356) 
Consequently from (356) and (355) 
357 
" hô ( 7) 
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