6 
The method of generating the image profile boun 
daries is shown in Figure 3. The magnetic tape con 
taining the digital profile data from the AS-11B-1 is 
read in by the Ampex unit. The decimal shutdown tape 
is read in for the particular photo, allowing the interior 
orientation of the photo to be determined after a reading 
of the four fiducials. The controller then reads in two 
profiles and determines the path to be followed in the 
input photo (between the two elevation profile paths). 
The computer performs a model-to-photo coordinate trans 
formation for the area 1, 2, 3 and 4. This transformation 
can include several corrections such as earth curvature, 
atmospheric refraction, model distortion, and lens distor 
tion. From these four coordinate positions X and Y 
commands are generated to move the input photo from 
point 5 to 6, and commands are also generated to translate 
the output drum in the Model Y direction. Simultaneously 
with this the four photo positions are used by the com 
puter to calculate the commands for the zoom optics 
and rotation of the line element. At the end of the 
first printed swath, the third profile data is read 
in and the first is discarded. The next print path 
is in the reverse direction, using data from profiles 
2 and 3. This process repeats itself for each profile 
in turn, within the boundaries established by the operator, 
until the area has been covered. 
By the process described above the measured co 
ordinate information relates to the terrain along the 
boundaries of the swath being printed, rather than to 
the terrain along the center line of the strip. The 
latter situation would result in possible errors in 
image placement along the edges of strips. Thus, the 
Off-Line Printer provides a continuous image in all 
directions, offering an aesthetic quality not common 
in orthophoto imagery, particularly when fairly wide 
profiles are generated. In the Off-Line printer the 
width of the profile does not affect the quality of 
the image. However, the accuracy of the locations of 
image points between the profile data strings then becomes 
a function of terrain slope or terrain inflection. 
The ability to dynamically rotate the filament, 
change magnification, provide the necessary differential 
movements of the input photo in X and Y, and to analytic 
ally determine the appropriate photo X and Y positions 
provides the universal aspect of the Off-Line Orthophoto 
Printer. With additional software programs the printer 
could provide other transformations - e.g., radar and 
XR restitution.