- 
  
19. 
Table III. Comparison between A-7 and automatic contouring 
for 1:50, 000 photographs 
  
Contour Length Average Average 
Errors, cm? 
  
  
Average height, used planimetric elevation Average, 
slope, % m km error, mm positive negative error,m m 
2 120 4.1 3.6 2.2 12.6 0.7 
2.5 160 3.4 10.0 2.8 31.2 2.5 
3 150 0.6 6.8 1.3 2.8 2.0 1.7 
3.5 160 2.4 6.9 0.0 16.6 2.4 : 
4 140 0.9 2.6 0.7 1.6 1.0 
4 130 1.8 3.9 3.4 3.7 1.6 
8 140^ 13.2 4,1 4.5 49. 6 3.3 ) 2.7 
8 140 1.0 2.6 0.0 2.1 2.1 : 
20 170 0.6 3.9 0.0 2.3 6.4 
20 150 0.6 3.3 0.0 2.0 6.6 | 6.2 
20 160 0.6 2.8 0.0 1.7 5,6 
28 150 0.6 2.1 0.0 1.3 6.1 
28 170 0.6 2.0 0.0 1.2 5.6 ; 5.0 
28 170 0.6 1.2 0.0 0.7 3.3 
  
* The only contour line whose entire length was used. 
In columns 5 and 6 of Table III the positive and negative error surfaces 
are given separately so that the approximate shift is directly visible. For all con- 
tour lines negative errors prevail and often the whole portion of a contour line under 
investigation was on one side of the corresponding A-7 contour line. Figure 14 shows 
the comparison between the A-7 and the automatic contours and the theoretical 
error curve for photo scale 1:50, 000, for which a theoretical contouring accuracy of 
mh = 1.5 + 10 tan 4, in meters, 
was accepted. 
A ACCURACY OF AUTOMATIC CONTOURING 
FROM 1:50 O00 PHOTOGRAPHS 
O Differences: Automatic -A 7 
O Theoretical accuracy 
my, =(1.5 +10 tan e)m 
  
Average height errors of contours 
T 
4A 
  
Slope in % 
30% 
Oo 
a 
o 
o 
ro 
o 
ro 
on