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Inner Orientation. The flowchart in Appendix A-2 describes control during 
the inner orientation of photographs. In the first phase the operator 
identifies the photographs and determines if fiducial transformation is 
needed or supported by available information. If the answer is negative the 
fiducial pattern attribute is entered, which allows for an automatic stage 
positioning from fiducial to fiducial. When fiducial transformation is 
requested, the available information table is loaded from disk. . From the 
format and number of” records in this table the computer recognizes 
automatically which type of transformation is feasible and a corresponding 
attribude TRFM is assigned. The first hardware related function is the 
approximate centration of photographs followed by indefinite measurement 
cycles, interrupted by switch Al to record fiducial coordinates or, for a 
non-standard pattern, by switch A4 to terminate the measurement cycle. 
Depending on the transformation flag (TRFM-F) and attribute (TRFM) a suitable 
transformation is computer selected.  Affine transformation (with three 
parameters) is standard when four calibrated fiducials are available, whereas 
bilinear transformation (with four parameters) is applied for photos with 
more than four fiducials. When only calibrated distances are computer 
detected in the fiducial information, a simple transformation (with two 
parameters) to correct for film shrinkage is implemented. 
Model Formation. The operational control during the main triangulation phase 
is flowcharted in Appendix A-3. Here again, an indefinite program loop 
allows for measurements in a real-time positioning mode RTP/B (see Figures 1 
and 3), interrupted for recording when action switch Al is depressed, or 
terminated with action switch A4 when driving pattern is completed. Other 
action switches support ancillary functions, such as the display of current 
orientation parameters (A2), visiting of other points (A3) or the 
cancellation of the last point (A5). When A4 is applied two times in a 
sequence data snooping and display is activated. The computer controlled 
recording and computations are eventually followed by data editing. The 
operator's interaction here is conversational and allows for three functions: 
ADD, REPLACE and DELETE. When editing is finished and mode switch M4 engaged 
the RESEAU subroutine is called which facilitates auxiliary measurement on 
réseau marks. Before all measured information is finally stored in data 
banks a mandatory check on a suitable reference point makes it possible to 
discover potential coordinate encoder malfunction during the model 
orientation, so that the whole process MODEL can be repeated. 
Tie Point Identification and Transfer 
Ties between Models. In NRC triangulations the tie points within a single 
strip are selected during the operations, without any preliminary 
identification, marking and numbering. The tie points in the following 
models are then identified by their photo coordinates in the common 
photograph. As long as the number and position of required tie points 
between models is standard, the computer also takes care of automatically 
assigning them unique identification numbers. These tie points do not even 
have to be well defined in planimetry, as long as their parallaxes can be 
measured accurately. In order to measure a tie point in the current model 
the computer positions the old photograph using the coordinates recorded from 
the previous model, and blocks any unwanted manual displacement from this 
given position until the stereomeasurement in the new photograph and the 
recording is completed. 
If it happens that the tie point position in the new model is established 
with some minute discrepancies caused by an imperfect function of the servo-