EE AE ET ERA RES IE APE IR 
FER AURI 
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Y— coordinate of the projection centre 
indicate that for high-precision problems 
the pre-calibration of the  focusabie 
cameras does not satisfy the accuracy 
requirements. It is necessary to use the 
method of simultaneous calibration in 
which the elements of the internal and 
external orientation are determined 
together using photos of the object and 
of control points suitably distributed in 
the object space simultaneously with the 
solution of the photogrammetry problem. 
4. The elimination of the lens distortion 
stabilizes the values of €f and Ys 
obtained from the different photos and 
improves the accuracy. Thus before 
calibration a correction of the image 
coordinates with a pre-set lens 
distortion is recommended instead of 
increasing the number of the control 
points necessary for the analytical 
determination of the lens distortion. 
SIMULTANEOUS CALIBRATION 
The established differences in the 
analytically determined values of f and 
Ys, obtained from different photos 
motivate the necessity for simultaneous 
calibration for each photo, taken with a 
focusable camera. If for the purpose of 
improving the accuracy of the solution of 
the photogrammetric problem a double or 
triple fixing of the object state from 
each camera station is done, simultaneous 
calibration and determination of the 
external orientational elements for each 
photo is necessary. To avoid averaging of 
the photogrammetric results from all 
photos a method for the simultaneous 
adjustment of the data obtained from the 
multiple photography of the object from 
two or more camera stations with a 
simultaneous calibration and 
determination of the external orientation 
elements. The calibration and the 
determination of the external orientation 
elements can be done by common or by 
individual elements for the photos taken 
from the same station. 
The analytical solution is based on the 
collinearity condition and aliows a 
simultaneous adjustment of the data from 
multiple photography of the object from 
two or more camera stations. Each photo 
participates independently in the 
adjustment, and the internal and external 
orientation elements are determined 
simultaneously with the solution of the 
photogrammetric problem. The method is 
analogous to the block phototriangulation 
by bundle adjustment. 
Computer program 
On the basis of the method mentioned 
above a program is created which allows 
the accomplishment of following: 
  
(i) pre-calibration of cameras by a test 
object  -with or without determination 
or elimination the lens distortion 
(ii)calibration of photographs in the 
process of solution of the photogram- 
metric problem: 
- with camera calibration elements 
common to all photos, taken from 
all stations; 
- with orientation elements common 
to ali photos, taken from one 
station; 
- with camera calibration elements 
different for each photo; 
(iiijcalibration of all or of only some 
camera parameters; 
(iv) only a correction of the measured 
values of the camera external 
orientation elements obtained by a 
pre-calibration. 
Experiments 
The method and the program described 
above were experimented on a test object 
photographed from two camera station with 
three photoplates each. The following 
cases were experimented: 
ti) for different number of unknown 
elements of internal and external 
orientation: 
6 elements -the external orientation 
elements only, 
7 elements - the same 6 elements 
plus the focal lenght, 
9 elements - the same 7 elements 
plus the prinsiple point 
coordinates of the photo, 
10 elements - the same 9 elements 
plus the first radial 
distortion coefficent, 
712 elements - the same 10 elements 
plus the second and third 
radial distortion  coeffi- 
cients, 
(iij in the case of simultaneous 
calibration and determination of the 
orientation elements, using one, two 
Or three photographs from each 
station (simultaneous adjustment); 
(iii)in the case of different number and 
distribution of the control points. 
The standard errors and RMS errors 
obtained for some of the experimental 
cases are give in Table 1. 
The photogrammetrically obtained spatial 
coordinates of the points are compared 
with the geodetically determined ones. 
The root mean square errors allong each 
coordinates axis have been computed from 
their differences and used as criteria of 
accuracy of the solution. The following 
accuracy can be considered as realized: 
nm 1,5 mm , m, - 5 mm , m, = | mme