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system to the machine coordinate system. These constants 
are applied to the equations which define the x-y photocoordinates 
in terms of model coordinates and the rearranged orientation 
matrix elements. The updated equations thereby reflect the 
precise diapositive orientation on the scanning tables. This 
operation takes approximately one minute. 
e. The computer then automatically directs the 
scanning tables to recover conjugate image points on each 
diapositive for a predetermined check point or series of 
check points. All data and operations are verified in this 
manner since the computer uses the preprogrammed XYZ ground 
coordinates and the newly input data to compute and position 
the scanners to the photo coordinate positions on the glass 
diapositive plates. If the check points are off and a quick 
analysis determines the source of the error, it is corrected 
immediately. If not, the model is temporarily by-passed and 
the next model set up. A separate group would recheck 
the input data and data tapes for error and rectify any mi stakes. 
If the check points are within acceptable limits, the 
operator either presses the '"GO" key and enters the symbol 
printout routine, step 7 to follow, or presses the "ADV-AR" 
(adverse atea) key to outline areas where special automatic or 
semi-automatic operating procedures are clearly required. 
f. The Adverse Area routine enables the operator 
to establish sequences of x-y photo coordinates, in 4 millimeter 
increments, which encompass one or more troublesome areas. 
There are separate commands for such areas - i.e., Hold Altitude, 
Manual Profiling, Manual, Positioning, three different speed 
commands, etc. Hold Altitude automatically locks the AZ-counter 
at the last known elevation until the instrument is out of 
the area. Manual Positioning stops the instrument to allow the 
operator to intervene. The Manual Profiling and Speed Control 
commands are self-explanatory. The areas that usually need 
special consideration are extended water areas, cloud covered 
areas, excessively dark or light areas, extremely steep cliff- 
like areas, occluded areas in oblique photography etc. After 
defining all adverse areas the operator presses the "END" key 
and the instrument automatically enters the symbol printout 
mode. 
g. The printout is automatic and follows a predetermined 
program stored on the input data tape. Symbols which can be 
exposed on both the orthophoto and contour film sheets are those 
for: control points, pass points and UTM grid intersections. 
At the end of the symbol printout routine the scanning tables 
are driven to the starting point, which is the lower left 
corner of the compilation limits. The printout tables are 
in turn driven to their starting point. 
39