Bel gr N TE 
  
  
  
  
  
  
  
  
  
  
  
  
2 
have also been measured in the control points which are located in ac- 
cordance with the figures 1—3. 
7. The measured y-parallaxes have been corrected with respect to the 
systematic errors under point 2 and, if necessary, the discrepancies un- 
der point 3. The standard errors of the y-parallax measurements have 
been computed according to the formulas in for instance [2]. 
8. The preliminary machine coordinates of all points have been cor- 
rected in accordance with a method, described in [2]. The procedure is 
in summary: From the measured and corrected y-parallaxes in the usual 
6 orientation points and from the corrected elevation discrepancies in 
the scale transfer points, corrections are computed to the individual 
projectors according to the Bachmann formulae. Then, the preliminary 
machine coordinates in each model are corrected from the individual 
projector corrections. The necessary formulae have been summarized 
in [2], expressions 6.1 — 6.5, 7.1 — 7.6, 4.1, 4.3 and 4.5. 
9. 'The final machine coordinates have been transformed into ground 
coordinates by scale change, translations and rotations of the entire strip 
with the aid of the control points. Three different cases concerning the 
number and locations of the control points are assumed. See fig. 1—3. 
For the coordinate transformation the weights of the corrected ma- 
chine coordinates with respect to the accidental errors of the measure- 
ments of parallaxes and coordinates have been introduced and finally 
the weights of the transformed coordinates have been determined under 
the three different assumed conditions. 
Below the formula systems will be summarized and the standard er- 
rors of the final ground coordinates will be graphicaily demonstrated 
for the different cases. A more detailed derivation of the formula 
systems will be published later. 
The fundamental error propagation formulae 
In [4] Bachmann has derived the fundamental summation formulae 
for the aerotriangulation. With slight changes of signs as indicated in 
[2] we have the total errors of the elements of the external orientation 
of the n:th picture after the triangulation as: 
i—n 
Di, = > du, (1) 
i—1 
Dg, = Ÿ dy; (2) 
i—1 
Des, = 3 des, (3) 
i _— 1 
— n 
Dby, — b $ (n — i)dx, + Ÿ dby, (4) 
id ii