226 
If we connect the equations 3 and 4 with a new equa 
tion 6 where the effective spatial frequency is sub 
stituted by the limiting spatial frequency thus we 
have a basis for planning surveying flights 
(R g - limiting spatial frequency, R* - true 
spatial frequency, h«, - altitude, f - focal 
length) Dependent on a desired result of a surveying 
flight we can forecast seme conditions 
obtainable distinguishing details for given altitude 
objective and fils 
R w =R a If/(hfl-f)3 
highest altitude for a reproduction of details to be 
obtained and given objective and fils 
h g =f[iR a /R w /+11 (S' 
necessary objective for given altitude and reproduc 
tion of details to be obtained 
f=hJR"/(R t 
Vi) 
necessary fils aaterial for a reproduction of details 
to be obtained and given altitude and casera (objec 
tive) 
s F (R a )=l/n8s a (R i 
(18) 
(m F (R g ) - modulation grade of film at limiting 
spatial frequency, m°(R g ) - modulation grade of 
objective at limiting spatial frequency) Based on the 
value of m F {R fl ) we can look into the data sheets 
of different film materials. 
Based on the above mentioned two systems, camera LrSK 
with aerial film VF 45 and camera 8SK 4 with aerial 
film VF 45, we made surveying flights at different 
altitudes. The obtained air photos show the correct 
ness of the above conclusions.