The non-linear observation equations for the image coordinates can be 
formulated according to the condition of collinearity: 
  
  
x; pe SP DA OI di) 
i j X » - J ^ ^ t ^ ^ 3 A X ram 
| €? 713,3 0374 725 5, Fa (3, -8,) 
ad f o4, EU me UI, ied, 
i,j V ° . - 3 A ^ Vea ^ ^ 3 P 2 2 
nisl Fel Rs 15, y 35 yii) 
with: 
- image coordinates of point Pi in image I; 
  
A A : ° 
hes Yau = residuals of Xi Yi j 
fj = calibrated. focal length of image Ij 
xi 3 2, = unknown object coordinates of point P, 
X; VIT 2, = Unknown object coordinates of the perspective 
centre of image lj 
^ “A 3 3 ^ 
rud ver 33. j = Unknown elements of the rotation matrix R, of 
image I; with three independent rotation para- 
meters Wy $i Kj 
Because it is not possible to determine the exterior orientation of all 
images I; So-called orientation images Ik (k=1...1) are introduced. The 
exterior Orientation is in fact only computed for the images It. 
The parameters of an image I; are then represented as functions of the 
parameters of neighbouring orientation images. In case of linear func- 
d, |, -d, d.-d, 
Xx. = ki jd X 
j k 
d 17d, di 41 7d, 
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