Ap =B In: H-h -Axhj - (x-B)Aho (2) 
ie ana 
  
  
x H-h-Ah 2 H-h 
where Ap ‘ = error in x-parallax 
x 
Ah ‚Ah = profiling errors in the orthophoto and the 
1 2  stereomate, respectively 
X 7 X-coordinate in the stereomodel measured from 
the orthophoto nadir point. 
When Ah -Ah = Ah, which is the case when the orthophoto and the 
i 2 
stereomate are based on identical profiles, equation (2) becomes 
Ab = Bin ' H-h — BAh (21) 
x H-h-Ah H-h 
The following example will demonstrate the effect of a small scanning 
error Àh on the x-parallax error Ap : 
X 
H = 600 mm 
B = 360 mm 
. h = 50 mm 
Ah = 0.2 mm 
Substitution of these values into equation (2') gives 
^p = 0.13093 m» - 0.13091 mm x O0 
x 
It is therefore obvious that the production of stereo-orthophotos 
should be based on identical profiles in order to minimize the effect 
of profiling errors on the x-parallax in the stereo-orthophoto pair. 
In addition, this mode of operation will prevent the introduction of 
y-parallaxes in the stereo-orthophoto model as a result of profiling 
errors. T 
These basic operational requirements could not be realized in the 
temporarily modified SFOM equipment which was used in the experiments 
described later. The effect of Scanning errors on the vertical infor- 
mation obtained with this equipment can be estimated by setting as 
before: 
H = 600 um 
B = 360 mm 
h = 50 mm 
and assuming 
^h = -0.2 m 
1 
Ah = 40.2 mm 
2 
The followin; 
The above ex: 
the orthophot 
the x-parall: 
next are affe 
results are c 
ment, such as 
Experimental 
a. Individuz 
Two stere 
on the modifi 
used for eval 
points. Dist 
corners, were 
points on the 
Their elevati 
the x-paralla 
coordinates w 
the stereomod 
of coordinate 
conformal tra 
. coordinate di 
errors. They 
Err 
  
Orthophoto 
Scale 
  
  
1:4000 
1:2000 
  
  
b. Contour 1 
The accur 
using the Ste 
mapping proje 
at the scales 
the original 
intervals wer