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In more detail the algorithms for solving photometric 
problems are given in the publication (Matiyasevich L # , 1980). 
Estimation of the sample values of mathematical expectation, 
mean-square error and other statistical characteristics is 
accomplished with the use of conventional probability theory 
formulae, and determination of the spatial-frequency spectrum - 
following the standard technique for analysis of random pro 
cesses (Bendat J., Pearsol A., 1974)* 
The computation program is so designed that it is possible, 
depending on the problems being handled, to delete some units. 
In such a case the values of azimuth and height of the Sun, 
required for subsequent computations shall not be computed 
and shall be entered into the computer as initial data. Or the 
operations for computation of the spatial-frequency spectrum, 
density and function of distribution can be eliminated,if the 
size of the object makes it impossible to obtain the sufficient 
volume of sampling of the values of ZLE of the object elements. 
Accuracy of photometric measurements 
The major photometric value the accuracy of determining 
of whicn affects the accuracy of determining of other sought 
values is the ZLE. Theoretically, the accuracy of deter 
mining of the ZLE can be found if the MSEs of the values of 
the arguments are known the function of which the ZLE is. The 
conducted calculations have shown that in determining parame 
ters of the equipment with relative MSE of the order of 5% 
and characteristics of the survey conditions - with MSE 10%, 
the relative MSE of determining of ZLE of dark objects (ZLE = 
0.1) may reach 50%, and for bright objects (ZLE = 0.5) - 25%. 
Having increased the accuracy of determining of the ini 
tial data, we can reduce the above-mentioned values of errors 
in determining the ZLF. Besides, it should be noted that the 
obtained values contain random and systematic components. Eor 
the given film the errors in the parameters of the surveying 
system are constant and systematic in character. Eor the given 
frame the errors of some characteristic of survey conditions 
(intensity of terrain illumination, albedo of the terrain, 
parameters of the atmosphere, etc) also assume constant, 
systematic character.