473 
Replicated measurements gave a setting precision of 6.46 ¡xm, which 
does not differ significantly from sx,y- 
Then, a small wire of 1.3 mm 0 was introduced between the frame 
and the glass plate. Four plates were exposed with the wire in various 
positions. The results of the computations are shown in table 1. A 
comparison between the standard error of unit weight s 0 and the 
precision sx,y can be performed with an F-test. If the ratio s 0 2 /s 2 x, y 
exceeds F0.95 (2,40) = 3.23, it is necessary to investigate whether the 
plate has been bent or lacks of flatness. However, it would be best to 
discard that plate. 
Table 1. 
Plate 
dc lx m 
dX H / W m 
dY H' 
SO n m 
F 
Note 
1 
+ 710 
— 1538 
+ 1300 
103 
149.5 
Cannot be used. 
2 
+ 679 
— 1355 
— 323 
29 
11.8 
Can be used after correc- 
3 
+ 594 
— 543 
+ 920 
11 
1.70 
tion. 
Can be used after correc- 
4 
+ 1158 
+ 213 
+ 3130 
7 
0.69 
tion. 
References: 
1. Finsterwalder, S.: Über die Konstruktion von Hôhenkarten aus Ballonauf- 
nahmen. K. Bayer. Akad. d. Wiss .1900, Bd XXX Heft II, S. 149—164. 
2. Hallert-Ottoson: General differential formulae of the complete projective 
relations between planes. Transactions of the Royal Institute of Tech 
nology Stockholm, Sweden. No 140, 1959. Udc 526.918.7.