generated in the course of planning of the photographic operation. Such 
planning, in turn, is normally accomplished with the aid of the simulator 
to be discussed in due course. 
The least squares resection generates approximate angular elements of 
orientation and revised approximations for the coordinates of the camera. 
It also detects and edits out blunders that may have been made in designa- 
tion of approximate X,Y,Z coordinates of the points used. 
3.4 PRELIMINARY TRIANGULATION 
Once all plates have been measured, a sort is executed by the computer 
to generate a file designating all comparator measurements for each point. 
From this file and from the results of the preliminary resections the reduc- 
tion proceeds to perform a preliminary least squares triangulation in order 
to generate approximate X,Y,Z coordinates for each point. During this 
reduction, automatic editing is again performed to detect blunders which 
at this stage mostly result from misidentification of points. During pre- 
liminary triangulation refinements to the preliminary corrections for lens 
distortion are also made, provided distortion coefficients corresponding to 
two distinct distances have been specified. Otherwise such refinement must 
depend on the process of self-calibration which can be executed in the 
bundle adjustment. 
3.5 THE BUNDLE ADJUSTMENT STAR 
The separately executed processes of triangulation and resection 
employed in the preliminary reduction are executed simultaneously in the 
program STAR which is an acronym for Simultaneous Triangulation And Resec- 
tion which, in turn, is a description of what is accomplished in a bundle 
adjustment. More specifically, STAR is a bundle adjustment with self- 
calibration accomodating as many as 6 different cameras and as many as 24 
separate exposures (not counting the various exposures merged in certain of 
the scenarios for preprocessing of multiple exposures). 
In STAR, any control that may be available is exercised with appro- 
priate a priori constraints specified by covariance matrices. In situations 
involving strong geometrical configurations, STAR may be advantageously 
executed without recourse to control (beyond the bare minimum needed to 
define the coordinate system to be adopted). Whatever control is exercised, 
STAR upon converging will perform an extra iteration dropping all control 
and executing a free net adjustment employing the immer adjustment con- 
straints developed by Blaha (1972). In the free net adjustment, the coor- 
dinate system is so defined as to generate a covariance matrix of the 
entire set of triangulated coordinates having a minimum trace (sum of dia- 
gonal elements). In this sense, the coordinate system is defined to pro- 
duce results of highest possible overall accuracy. 
In the self-calibration mode STAR can exercise up to nine error 
coefficients for each camera. These consist of any combination of: three 
elements of interior orientation Xp,Yp,C; up to four coefficients for 
radial distortion K;,K2,K3,Ky4; and two coefficients for decentering dis- 
tortion, P;,P,. Each exposure taken by a given camera shares a common set 
of error coefficients. When the maximum of 24 exposures from 6 different 
cameras is exercised, the reduced system of normal equations is of order 
198 (6 x 24 = 144 elements of orientationplus 6 x 9 = 54 error coefficients). 
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