494 
6 c) The differences in elevation, calculated from formula (3) have 
been corrected for 0,§06 difference in nadir-directions. A new 
calculation has then been performed with the formulas given in 
(3). 
The average residual error of the elevation-measured points was 
calculated to be 0.33 metres according to method 6 b. The calculation 
according to method 6 c gave the value 0.05 metres. 
In fig. 3 the results according to 6 a and 6 b have been compared. 
Table 1. 
Circle No. 
Magnitude of radial distortion 
according to method: 
6 a 
6 b 
6 c 
1 
+ 4.1 
+ 8.7 
+ 4.0 
2 
+ 7.5 
+ 9.5 
+ 7.4 
3 
+ 9.5 
+ 6.8 
+ 9.4 
4 
+ 9.4 
+ 4.2 
+ 9.2 
5 
+ 6.5 
+ 1.4 
+ 6.4 
6 
0 
0 
0 
7 
— 10.7 
— 8.5 
— 11.1 
8 
— 26.4 
— 21.5 
— 24.5 
9 
— 47.7 
— 39.1 
— 47.0 
Literature: 
Hallert, B.: The grid method and the Y-parallax method for determination 
of systematic disturbances in aerial and terrestrial photographs. — 
Stockholm 1956. 
Hallert, B.: The influence of radial distortion and other systematic errors 
upon photogrammetric models from approximately vertical pictures. — 
Stockholm 1956. 
Rikets allmanna kartverks meddelande nr 27 — Stockholm 1956 (Some 
Investigations Into Distortion of Survey Cameras). — Also published 
separately in 1956 by L. Ekelund, Stockholm.