433 
it was found that s 2 = 0.003 mm by using the condition that the 
measure crosses would be located on a straight line. S3 has been com 
puted from s0 and s() according to (25). The result is a follows 
s 3 s 3 
Strip 6010a 0 0.028 mm £2 0.027 mm 
,, 6010b 0 0.013 mm £2 0.016 mm 
„ 6011 0 0.016 mm £2 0.038 mm 
Root mean 
square value 0 0.022 mm £2 0.027 mm 
According to the F-distribution mentioned above the greatest values 
deviate significantly from the lowest values. As the image quality has 
been rather uneven, it must give raise to significant deviations. In the 
strip 6011 one horizon for £2 has been very unsharp, which has caused 
the lower precision. The other horizon have been sharp or partly 
sharp. Three horizon in the strip 6010a have been unsharp. Three 
horizon in the strip 6010 b sharp or partly sharp and one horizon has 
not been measurable. It is obvious that the quality of the pictures and 
the precision are strongly correlated with eachother. The low precision 
values indicate that it has been difficult to measure a great deal of 
the horizon pictures. 
8. The accuracy of the inclinations from the horizon pictures. 
The inclinations from the horizon pictures are compared with those 
from the autograph A8 for determining the accuracy in accordance 
with the method mentioned above. As the horizon camera gives only the 
angle differences between the reference horizon and the other horizons, 
the absolute values are not comparable. Therefore all the A8-values 
have been reduced in such a way that the reference horizon has became 
zero. The differences between the A8-valus and the horizon camera 
values are according to the chi 2 -test normally distributed on the 5 per 
cent level. (See histogram 1.) The laws of error propagation can 
therefore be applied. The accuracy is calculated from the differences. 
The horizon camera values and the A8-values are considered inde 
pendent of each others. As the accuracy of the A8-values was estimat 
ed, the accuracy of the horizon camera values can be obtained accord 
ing to the following formula 
s hk = V / s, lk+Afi 2 — s A8 2 (26) 
where 
S],] { = the standard error of the horizon camera values 
s as = ,, „ „ „ „ A8-values 
s hk-!-A8 = t^ e root mean square value of the differences between 
the both values.